July 21, 2020 • 41 mins
Daniel and Jorge talk about phonons, magnons, excitons, anyons and explainons.
Learn more about your ad-choices at https://www.iheartpodcastnetwork.com
See omnystudio.com/listener for privacy information.
Mark as Played
Transcript
Episode Transcript
Available transcripts are automatically generated. Complete accuracy is not guaranteed.
Speaker 1 (00:08):
Hey, Daniel, what am I made out of? You're made
of particles? Uh? And my lunch particles? What about the sun?
Also particles? Okay? Now what are all of those particles
made out of? Probably smaller particles, says it. Particles all
the way down. Is there anything that's not a particle?
You're asking a particle physicist, So what else do you
(00:29):
expect to hear? An actual particle of explanation? Well, I
think this podcast is basically a particle. Is it made
out of? Explain eons? Bad punions? Bad? I had a
bad punion last week. Didn't go over well? Hi or
(01:00):
handmade cartoonists and the creator of PhD Comics. Hi, I'm Daniel.
I'm a real particle physicist, not a quasi particle physicist.
Welcome to our podcast, Daniel and Jorge Quasi Explain the Universe,
a real production of Radio That's Right, in which we
talk about all the things that are real, all the
things that are crazy, and all the things that are imagined,
and our interpretation of all of them. We break them
(01:23):
down for you and try to give you an understanding
of what's going on out there and how scientists are
thinking about it all the mysteries of the universe, all
the unanswered questions, and all the amazing facts that we
have learned. We bring it all to you with a
pun or two. It's right, all of the things that
are out there and all the things that might also
be out there that scientists are not sure actually exist
(01:44):
or are even real, even some things that could be
semi real. Isn't that a weird term, Daniel, semi real
almost real? It's semi weird. Yeah. Yeah, Well, you know
there's a whole rabbit hole we could get down into
there by like what is real even mean? Man? But
I don't think we've smoked enough banana pee is yet
today to get there, or like our rabbits even real.
That's another rabbit hole in itself. And why are they
(02:05):
chasing bananas down rabbit holes? Like that never made any sense. Yeah,
So everything's a particle. It seems like, you know, all
matter in the universe, And so it kind of begs
the question like what are particles themselves made out of
and what is not made out of particles? And could
there be something else that's not a particle but still
make up matter? Yeah, And particles are sort of an
idea that we have. I mean, we look out in
(02:27):
the universe and we break things up and we see
them as smaller and smaller bits, and then we have
this notion that the smallest piece might be this dot.
But the whole concept of a particle is a little
bit fuzzy. We've talked on the podcast about the discovery
of particles. Whate really means to be a particle? You know,
the first particle ever discovered was the electron. It was
really just the identification of a point in space that
(02:49):
where you had charge and mass at the same time,
like this little cluster of quantum labels. And since then
we've added stuff to it. You know, particles can have spin,
that can have magnetic moments, that can do all sorts
of crazy stuff. But still this concept of like what
is a particle what does it mean remains a little
bit fuzzy. You know, they don't have any volume, They
do all sorts of weird things. Sometimes they act like waves,
(03:12):
and so it begs the question of like our particles
real or they're just something sort of in our mind?
And can we apply this notion of particles to other things? Also, now, Daniel,
as a disclaimer, we we should say that you are
a particle physicist, so you might not be entirely neutral
on this subject, might be a little biased. Or I'm
an expert, right, so you should you should listen carefully
(03:32):
to my thoughts about it, because I'm well informed. No,
it's certainly true, and I like to think of the
universe in terms of particles. I'd like to think that
the universe can be explained in terms of a bunch
of little microscopic things, that everything is really just an
emergent phenomena of the microscopic I guess a particle physicists,
everything looks like a party, just like I've heard astronomers say,
we're all made out of stars. I'm like, mmmm, that's convenient. Yeah,
(03:57):
And it's sort of a question of scale. Even astronomers
some times they treat like the whole sun as a particle.
You know, when you're doing your gravitational calculations about you know,
moving a planet around a star, you don't really care
about how big the star is. You're so far from
it that you can effectively treat the whole star as
if it was a point mass at the center of
mass of the star. And that's basically calling it a particle.
(04:19):
It's saying, I don't care about any other details. I'm
just gonna put it as a point. So it's a
very powerful concept, even if you're not gainfully employed in
the field. Right, And generally speaking, it just kind of
means like a packet of stuff, right, Yeah, it's sort
of like a little cluster of labels. You know, you
can put a mass on and a spin on it,
you know, other kind of quantum labels. But yeah, it's
like a little cluster of labels. Yeah, like a whole
(04:41):
bunch of little labels moving around together. Yeah. Like we've
talked about how the new trino, you know, it carries
a weak label but doesn't carry one for the strong force,
and if photons don't carry any mass, but they do
carry information about electromagnetic fields. And so to me, I
think about these things having their little dots in space
that have labels on them. And so there's this concept
in physics called a quasi particle. Is it quasi or
(05:04):
quasi part I'm quasi sure that it's quasi particle. Obviously
quasi experts in vocabulary here and pronunciation. If we're wrong,
we're only quasi wrong. It's better than being semi wrong,
I guess or pseudo wrong, pseudo experts. There you go.
And this came to us from listeners actually who had
a question about what these things are. Listeners, Linda Campbell,
(05:26):
Nick Beatrice, Jack Case, Tim Davis, they all wrote to
us asking what a quasi particle is. That's right. If
you have a question about something you'd like us to
talk about, right to us, because we will actually answer
your email and sometimes even do a podcast on it.
And these folks had seen articles about quasi particles and
(05:49):
asked us to explain it. What is a quasi particle?
What does it mean? And have we gone too far
with this concept of particles? Impossible? You can't have enough particles,
said to a particle physicist, you can't have too many particles.
I mean, it's such a nice idea. Now we don't know, right,
like we don't know if particles go on forever, if
you can get down to the smallest possible particle, or
if you get small enough particles doesn't really work and
(06:11):
you need something else, like you know, pixels of space
or little strings or something else. But so far, it's
a very nice idea to explain the world around us,
Like if you have a hammer, everything looks like a nail.
If you have a particle collider, everything looks like a particle. Yeah.
And if particles have worked, then you extend the idea.
You're like, well, let's see if this would also help
us understand this other problem. And we do that in
(06:32):
physics and in math all the time. We take strategies
from one field and we apply them somewhere else to
see if we can make connections. You know, one of
Newton's greatest leaps forward conceptually was understanding that the same
rules applied in the heavens and on Earth. And that's
all we're trying to do. We're trying to use the
concept we discovered in particle physics, the group theory, the symmetry,
the conservation laws, and apply them other places. Yes, Daniel,
(06:54):
but what is heaven made out of particles? Particles, angel ons, halons?
There you go? Um. So, as usually, we were wondering
how many people out there actually had heard of this
concept or knew what it was. So Daniel went out
there into the wilds of the Internet to ask this
question and get people's responses. So before you listen to
(07:15):
these answers, think about it. For a second. Have you
heard of quasi particles and if somebody asked you, what
would you say. Here's what people had to say. Sounds
like something that has some of the properties of particles,
but perhaps doesn't satisfy all of the conditions. Either that
or some guy named quasi came up with a new particle,
probably something that wants to trick you that it's a particle,
(07:39):
and it's not guess that there are particles with more
than one. Quasi particles are virtual particles that don't follow
the rules. Crazy particles, particles which are created in the
vacuum because of the background energy of space that's sort
of there and they're not there. Maybe how that's how
(08:01):
that's something? Is that like a virtual particle or maybe
something that we've seen in the data when we've been
looking for particles that we can't quite explain. Particles have mass,
and quasi particles maybe doing maybe don't. Maybe they go
through a filter in the universe. Something that's almost a
(08:22):
particle or something very similar to one. I'm not a
native speaker and I had to look quasi in dictionary.
It can semi so coarse particle is semi particle, Quasi
means something that looks like something else. So I'm assuming
the quasi particle is a particle that looks like a
(08:45):
particle but really isn't. I would say a quasi particle
is a particle that may appear to be real, but
actually it's not. There was something super tiny. Well those
are some pretty good guesses. Yeah, I like the person
who looked it up in a dictionary. I'm like, I
know there's some rules here. You're not supposed to look
anything up or google anything, but you know, not being
a native speaker, I'll forgive them, right, Maybe there's just
(09:07):
quasi rules. So yeah, let's jump right into a daniel um.
What is a quasi particle. So a quasi particle is
called a quasi particle because it's something that behaves like
a particle, has some of the same properties that we
typically use to describe particles, like it's persistent, you know,
it sticks around. It's quantized. You know you can have
(09:27):
one or two without one and a half. Usually they're discreet,
but it's not actually fundamental. It's not like something that
is the building block of the universe. It's not a
ripple in the quantum field. It's usually like an excited
state of some macroscopic solid. It's something that behaves like
a particle, but it's not actually a particle. So does
that include like the protons and neutrons, you know, the
(09:51):
behavior like particles, but they're actually made out of smaller
particles inside. Is that kind of what you mean or
is it are you talking more like bigger scale? We're
talking bigger scale, I mean, and you could argue you
that protels and neutrons are not particles because they're not
fundamental and they don't have their own quantum fields, and
so in that sense, they really are an emergent phenomenon.
And we can get into that later on. I think
that's a fascinating question. But I think typically people think
(10:13):
when they talk about emergent phenomenon, they think about sort
of a larger scale. You know, imagine like you have
a glass of water in front of you and it
has that's sparkling. Water has bubbles. You can see those
bubble sort of move up through the water, and they
move sort of the way a particle does. They hold
their shape, they're consistent, you know, they're coherent. They move
through the water the same way a particle does. You
(10:34):
can apply a lot of the same mathematics and understanding
intuition that you apply to particles to that bubble in
the water, even though nobody thinks that bubbles are a
fundamental unit of the universe or that there's like a
quantum bubble fielding as a manifestation of maybe quarks are
made out of bubbles that we have yet discovered. Yeah,
it's bubble theory, you know, the same way you can
(10:55):
look at like the ocean and you can see a
wave moving through it. A wave is not a fundamental
proper of the universe. It's an emergent phenomena of all
these thousands and millions and trillions of particles all moving together.
But mathematically it's much more convenient to talk about the
wave than to track all the little particles that make
it up. So quasity particles in the same way, but
not really that big a scale on the scale, like
(11:17):
bubbles and waves, but you know, like excited states of solids,
like wiggles that pass through solids, or rotations of things
that move in a coherent way and and sort of
keep their identity as they pass through a solid, right
like sound waves. Also could a sound wave like a
shout or a screen be considered a quasi part of Yes,
sound waves like vibrations. Basically, if you break them down,
(11:39):
you can go down to like the quantum. The smallest
possible sound wave is like the vibration of a single
particle that is a quasi particle. It's called a phone on.
A phone on is like the I did not just
make that up. You can phone anybody and ask them
about it. It's seriously then, no, it's sort of like
(12:00):
a you know, it's a more general sense of what
a particle is. And here you have like a single
particle might be vibrating, and then it passes that vibration
off to the next particle and to the next particle
and the next thing. It's yeah, and it's quantized, right,
because these particles that are vibrating the atoms or whatever
in your lattice. You know, say, for example, I knock
on the desk in front of me, it sends sound
(12:22):
waves to the desk, or if I speak through the air.
Then those particles, the ones that are doing the wiggling,
their quantum particles. They have quantum states. It's like a
minimum amount of vibration that they can have. And so
if you have that minimum amount of vibration, they could
pass to the next one and pass to the next one.
And that's what keeps it like a coherent thing can't
just disperse out into infinitely smaller things. It sticks around
(12:45):
because of these quantum minimum They're almost like packets of stuff.
And it's sort of a mental game you can play
with yourself, like what's a particle and what's a quasi particle?
You know. Another great and classical example of a quasi
particle is the absence of a particle. What. Yeah, Like
you ever play that game where you have like a
bunch of tiles and there's one open slot and you
(13:07):
have to slide the tiles around, like get them in
the right order, like the little puzzles. Yeah, those little puzzles. Well,
you can think about it like as the motion of
a bunch of tiles, or you can think about it
as the motion of a hole of a gap. Right,
that gap is sort of moving through the puzzle. You're
moving that gap around, so that little hole is like
a particle. That little hole is sort of like another tile, right,
(13:28):
And so in the same way, if you have like
a whole bunch of electrons, you can think about one
missing electron moving around like they have a ten slots
for electrons, but only nine electrons, so there's one hole, right,
and then if all the electrons move over, then the
whole moves the opposite way, right, the opposite way precisely.
So you can either think of it as moving like
(13:49):
every single electron over one slot, or you can just
think of it as the whole moving over one in
the other direction. There's two equivalent ways to think about it,
but one of them is simpler because you've abstracted away
a lot of complications, so you can think about it
and just this one blob in the same way that
like watching a bubble rise through water is simpler than
thinking about all the billions of little particles that are
(14:11):
making that happen. So you sort of like abstracted away
some stuff so you can apply your particle brain to
this new kind of thing. I see, you just kind
of blew my mind a little bit. Yeah, just to
think of that. Bubbles are not actually a thing. They're
just like water, molic is moving out of the way.
That's a bubble, Yeah, exactly, They're just getting pushed out
of the way by that air. But the arrangement is
(14:32):
sort of static. There's like a minimum size to those bubbles,
right because of surface tension or whatever. The bubbles can't
just break up into infinitely small bubbles and that's why
they stick around right until they eventually they pop. And
in the same way, like electrons can't split in half,
and so that's why you don't get these holes like
gradually filled in with partial electrons. Now, this sounds kind
of very macro like, you know, we're talking about bubbles
(14:54):
and ways. Now, is this something that you use a
particle physics deals with or is it more like a
bigger things physics. Neither. Actually, it's not something that I
deal with because I usually deal with actual particles, real particles,
you know, particles that are excitations of quantum fields. But
it's also not something that happens on the macro scale.
Usually it's most often on the micro scale. So it's
(15:16):
something in the adjacent field of condensed matter physics. People
who build like weird materials and you know, super fluidity
and think about super conductivity. I mean, another great example
of a quasi particle are pairs of electrons that cause
super conductivity. You know, one reason that metals have a
hard time being super conductive is because electrons are fermions.
(15:37):
They don't like to be in the lowest state together
with another one. But in super conducting materials, we did
a whole podcast episode about that, electrons like to group
together into pairs. They're called Cooper pairs, and they're pushed
together into these pairs and together they're actually bosons. They
have the opposite rules from fermions, and so they can
cool down and all occupy the same state and flow
(15:59):
smoothly over each other. So a Cooper pair is like
a pair of electrons sort of acting like a particle.
And so that's another example of a quaty particle. They're
often at this micro level. I guess the common thread
is that they maintain some sort of quantum property, right,
like a dust particle. Physics wouldn't call a quasi particle, right,
It has to sort of maintain that quantuminez feeling about it. Yeah,
(16:21):
And you know, you could probably argue that anything as
a quasi particle, but I would say that it should
be persistent, and it should be quantized, and it should
be discreete. So many Q words quanti quasi qualitative, quantity
of particles exactly and so it's fun. It's like an extrapolation.
And this is always really fascinating in science when you
(16:41):
can see something in the world and then apply those
same ideas somewhere else and gain some insight because it
kind of works, you know, it helps you. It simplifies
the problems so you can see the larger dynamics and
gives you an insight into what's going on. It lets
you use your intuition from somewhere else. And that's what
science is all about. It's not about figuring out the
rules for a and there for being there for see,
we want rules that explain everything. We want rules to
(17:03):
tie everything together. And so yeah, if you have a
hammer and you've hit a bunch of nails successfully, you're
gonna go around and hit everything else with that hammer
until they look like nails, until they break apart into particles.
Very convenient. It all works, See, it all works. All right,
let's get into what are some examples, some fun examples
of quasi particles, and then let's talk about whether they
(17:23):
or not they're actually real. But first let's take a
quick break. Al Right, I know we're quasi talking about
quasi particles. I'm really talking about real particles. And even
(17:46):
this podcast is sort of a quasi particle, right, I guess,
because you know, it sort of exists as electrons moving,
which are particles, and it gets toward as information and
it gets turned into sound ways, which are sort of
quasi particles too. That's right. This part cast cannot be
broken up into smaller pieces, and so it's therefore a
quantized podcast and cannot disperse the universe and must be
(18:07):
accepted into your brain. In total. It's both good and
bad at the same time. You're welcome, of course, to
listen to the podcast in five minute increments or twelve
minute increments or five all at once, so do with
as you please, of course. Oh my goodness. All right, well,
what are some examples of quasi particles, Like we talked
a little bit about phonons being like sound waves particles. Yeah,
(18:28):
Phonons are vibrations, they're like the quantum of sound waves,
are like the minimum component of sound waves. All sound
waves in a solid are built out of phonons, and
so the smallest possible sound wave you can have in
a solid is one phone on and you know, it's
just like energy moving through the solid. This atom vibrating
in a lattice, and then the next one vibrates and
(18:49):
the next one vibrates, and so you can think of
that as the phone on moving through. And I think
phone on is pretty cool word to ye. It makes
me think of like some sort of like Star Trek gun,
like you know, set your phone on, blasters on, wiggle um,
I don't know, it's it's very reminiscent for me of
phoning it in. I feel like physicists phoned it in
(19:11):
when they came up with this name. They're like, what
do we call a sound wave particle? I know, a
phone on and I think it's awesome. Yeah, and then
all the other quasi particles all have sort of similar names.
You know, the kind of thing that's getting wiggled or
you know, moved through and then on at the end
of is it related to sort of like the medium
on which these things propagated or move around in, Because
(19:34):
I feel like a sound wave is quantized because the
underlying thing that they're on is quantized. So it's at
some point, you know, you can't make a smaller sound
wave because run into particle, that's right, because those particles
have quantized energy levels. Like, they can't wiggle at half
of their energy level. They can wiggle at one energy
level or two or three, but there's a minimum amount
(19:56):
of wiggle and that's why it's quantized. You know. That's why,
for example, they can't accept a photon of arbitrary energy.
They're resonant frequencies frequencies that solids like to accept photons
because it helps them move exactly one energy level up.
And also that's why solids give off light at certain frequencies,
because you know that's the resonant frequencies for that gas.
(20:17):
For example, I can excite up by absorbing a photon
and excite down by giving off that photon. And when
absorbs the photon, like, where does that energy go? It
goes into a phone on? Right. A phonon is the
energy moving through the gas. So photons get turned into phonons, right. Well,
that's fun to say. And so what are some other
(20:37):
examples of quasi particles? Well, basically every quantum property that
a particle can have when you put it in a lattice,
you can think about that property moving through the ladder.
What is like a like a grid of particles? Yeah,
every solid you can think of is like a grid
of particles, like a three D like a lego set
of particles put together. And so they're all back together,
(20:58):
back together. Each one is touching the one above and
below it into its left, into its right, forwards and backwards,
and they're sort of tied together by these bonds. And
that's what makes a solid, right, it's sort of like
a loose crystal. And so they're in this lattice so
they can pass information. Right, It's like if you're in
a crowd of people and everybody's whispering into their neighbor's ear,
you can pass information through the crowd, and so that
(21:19):
same way, like that's how these bonons get passed through
the crowd. But you can do it also with other
quantum properties like the particle spin. You said we could
do it with holes, but you can also do it
with like quantum properties like charge and mass and things
like that. That's a good point. I mean, for charge,
it's sort of holes, right. Holes essentially is the moving
of charge around, but they're the actual particle moves over,
(21:41):
like the electrons have to move over. You can't pass
charge from one particle to another the way you can
pass energy and electron moves from here or there, it
moves the charge with it, creating sort of like a
like a hole in the charge. Yeah, so you can
have quasi particles in like a particle gas right with
the electrons are free to move around. Then the apps
and of a particle is a quasi particle that whole.
(22:02):
But also in a lattice, you can have quasi particles
like the phonon, but also things like the magnon, which
is the the quantum of particle spin that helps create
the magnetic field that metals can have. For example. Now
that one does sound like a transformer, I have to say,
which I'm all for. Waits. A particle spin can also
(22:24):
move around like a wave. How does that work, Like
the orientation of it or what does that mean? Yeah,
the orientation of it. Remember, the particle spin is quantized.
So for example, an electron can be spin up or
spin down. So say you have a bunch of electrons
that are all spin down except for one that's spin up.
Then it can sort of pass that spin to the
next electron making its spin up, And it can pass
(22:45):
that spin to the next electron it can make its
spin up, so the spin up nous can move through
this sort of grid of electrons, and you can think
of that it's like, oh, well, I got a bunch
of electrons summer spin up and summer spin down. Or
you can think of it like, oh, I have a
magnon that's moving through a sea of electrons because like
one particle will give it's been to the next particle,
(23:08):
or or just from the gap of it. Yeah, they
can transfer because they couple to each other a little bit.
You know, Electrons talk to each other, they bounce around,
they share energy, they interact, and spin is conserved. So
you can't just like have them all be spin up.
If they're all spin down except for one, then you
have to have one electron spin up. It's just a
question of which one. And because it's quanti as, you
can't have like half spin up and a third spin up.
(23:31):
You need to pass the whole thing over from electron
to electron. And so the magnon moves around. Is it
like the potato in a game of pot potato? Exactly exactly,
But I'm not sure. Maybe the electrons want to be
spin up, right, Maybe it's like, hey, give me that
hot potato. No, give me that hot potato. I can't
speak for the electrons. We should just rename the game
to magnons or quasi potatoes, and then every time you
(23:55):
want to play with your four year olds, you have
to explain to them quasi particles, and then you know
they're not interested in anymore, and then nobody wants to play.
But these are actually really cool and they have other
applications and particle physics, like if you search for magnons,
you can be sensitive to really small effects. Like if
you get a field of particles and they're really quiet,
then you can look for magnons as evidence of like
(24:15):
maybe dark matter has come through and hit one of
these electrons and given it a spin, and so you
can try to measure these things using very very sensitive
magnetometers because remember the spin of the particle effects it's
magnetic field, and so that's why we call it a magnal.
It all goes back to dark matter, doesn't it. In
the end, it's only exciting if it can help you
find dark matter. I guess maybe right, because it motivates
(24:39):
why you want to study it. Maybe it's a big mystery. Yeah,
But here it's just like this is a cool idea
and it gives us a new way to look for
something really cool, and it's an example of why it
is good to use like particle physics ideas in other areas,
Like you can get this inside into condensed matter and
how spin moves around in the lattice of electrons, and
then that gives you an idea for how to look
(24:59):
for some thing else cool and news. So you know,
it's sort of like refreshes you creatively intellectually to like
look at something from a new perspective. So is the
idea then that, like if I have a whole bunch
of electrons and they're just hanging out and suddenly there's
like a potato in the middle, they're like, You're like,
must have been dark matter that gave us that potato, right,
or you know spin obviously, But is it kind of
(25:20):
like that, Like if there's suddenly a potato in the middle,
you've gotta wonder where that potato came from. Yeah, exactly,
And eventually one dark matter experiment will have to be
called potato based on this podcast, Yeah, physics ordinary what's
the right acronym there? Transfer Well, while you work on that,
you know, these things actually do have special power to
discover dark matter because the kind of dark matter experiments
(25:41):
we have right now are mostly waiting for dark matter
to bump into the nucleus of the atom, you know,
the big heavy protons and neutrons, and we see that
kind of nuclear recoil, You see that getting kicked, and
that requires kind of heavy dark matter, because you've got
to be big enough to like give it a kick.
The dark matter is really really whispy, then won't move
those neutrons and protons even if it does bump into them.
(26:03):
But these magnon detectors could be much more powerful as
a way to search for a very very light, very
low mass dark matter. And since we haven't found dark
matter at the higher masses where we've looked for it,
it's quite exciting to say, oh, look, we can build
new detectors that might be sensitive to even whispy or
dark matter. Because electrons are more sensitive than protons and neutrons,
(26:25):
well they're just lighter and so they're easier to kick. Right,
if you are a very light particle, then you're gonna
have a bigger effect bumping into an electron. Then you
are bumping into a proton or neutron, which is like
you know, a boulder in comparison. So if dark matter
can interact with electrons, then you would see it in
a very kind of maybe bigger way if you look
for these quantum spin quasi particles. Yeah, if you look
(26:50):
for Magnon's exactly. I feel like you don't want to say.
Magna is such a fun word. Yeah, Magnon, Magnon. And
there are lots of other kinds of quasi particles. You know,
there are polarns. This is when electrons interact with the
polarization of ions. Wait, I just came up with a joke, Daniel.
If you make this project, if you set up this experiment,
(27:10):
you should call it the Magnon Particle Interface Maximon Particle
Infation mp I, No Magnan p I. The ready for
prime time. Everybody has to unbutton their shirt two buttons
to work on this experiment. Yeah, and have a month.
I'll start growing it. Then there's the like there are
rotons if you have like a fluid rot If you
(27:32):
have a fluid, then you can get like vortices in it, right,
you can like little whirlpools and the sort of the
minimum amount of vortex that you can get turns out
to be quantized because of how these particles can spin,
and so that's what a roton is. It's like the
minimum quantum of vortices, I guess, because the medium again
is quantized, so you know, a little like vortices also
(27:55):
have to quantize because there's a minimum size to these particles. Yeah,
and they have energy levels, and just the same way
that phonons exist because solids and allattics have energy levels
to their vibrations. Fluids also have energy levels, and these
particles inside them, these vortices have sort of a minimum
energy level, and so that's that's where you get routons,
and then you get other really weird things. And you
(28:15):
can apply this really broadly, and it's been like an
explosion of different kinds of quasi particles people have sort
of created or or conceived of. You know, they even
have like weird two dimensional quasi particles. All right, let's
get into the rest of these quasi examples of quasi particles,
and then let's get into whether or not they're actually real,
(28:35):
like philosophically, could we call them real things? And how
does that maybe put into question the particles and we're
being out of But first let's take another quick break,
(28:57):
all right. I know, so we covered the phone on
the magnan and the rotons. What other ons of people
sort of discovered or study. One of my favorites is
this weird one. It's an excitation in plasma. So plasma
is like you take gas and you heat it up
so much that the electrons and the nucleus separate, right,
the electron becomes free, and you have like a charged
(29:19):
gas and this is really hot and nasty stuff, and
it's you know, it's what the sun is made out of,
and it's what we used to try to do fusion.
And sometimes you can get it acting in sort of
like sheets. You can get these like sheets of plasma
layering on top of each other because these things have
charges and so like you can get like a negatively
charged sheet and then a positively charged sheet, and then
(29:40):
a negatively charged sheet sort of like stack up on
top of each other, and weird ripples passed through these
two d sheets of plasma. And these things are called plasma.
That would be a good one, but no, they're called
for reasons I don't understand. They're called an eons but
(30:01):
like a n y on and you know, It makes
me wonder, like, how did they come up with that name?
Like maybe all the other as were taken and somebody said,
is there anything left ding oh anyon nons or something, Daniel,
what do you call a quasi particle made out of
quasi particles? A quasi quasi particle an on? Of course, Man,
(30:24):
I walked into all these terrible jigs you are, I
am just firing off the quasi pat chokes here. But
there's some really cool mathematical features of these things, Like
these anions they actually act like two dimensional particles. It's
like a mathematical system that we don't see in reality.
You know, our universe is in three dimensions, so our
particles move in three dimensions, and there's different mathematics that
(30:46):
apply to two dimensions, the surface of things and the
surface area of things, and how things diffuse, you know,
instead of going like one over our square, that goes
like one over our And these anions actually exhibit those
mathematical properties as if they were too d particles. And
that's really kind of cool. That's just like test out
these mathematics in real life interesting because then then you
(31:08):
can have like different kinds of physics, right like you
can have too D physics, which could be totally different. Yeah,
it is totally different, and it's fascinating to see it.
And like, of course it's made out of three D things,
so it's not really two D, but it's sort of
like a physical simulation of two D, which is really
pretty cool because you see these effects happening, but sort
of you know, quasi, there's like on the meta level,
(31:29):
you're like abstracted it out. And in this interpretation of
these plasma wiggles where I call these an eons and
treat them like particles that I see, that follows exactly
the math you would expect for actual two D particles,
and that's pretty cool. Like you can describe them with
wave functions even though they're they're not like they're just
gaps in other wave functions. Yeah, exactly, exactly. You can
(31:51):
describe them with wave functions and all the mathematics we
use for particle physics, but in two D. So that's
pretty awesome. All right, what are some other cool quasi particles?
I think maybe the That's what I'm excited about is
the exciton. There's actually a part of the exciton. Yeah,
and it's not like the quantum unit of Daniel's enthusiasm
(32:12):
for science. You know, it's has a minimum are you
saying there's a minimum excitability threshold always above zero? It's
always above zero. And this is when you get an electron,
which is a particle, you know, and a whole. So
a hole is already a quasi particle, right, it's the
absence of an electron. It's where it's a gap where
you might expect an electron. But sometimes electrons and holes
(32:36):
can interact with each other because that a whole is
in effect positively charged, right, The absence of a negative
charge is like a positive charge, and so the electron
and the whole can interact and they can actually form
these bound states. One electron will will drag a hole
behind it, and so they're sort of moving together. The
electron would drag the whole, Yeah, the electron will drag
(32:58):
the hole behind it, because you know, whole is sort
of like the absence of an electron. And you know,
these are all things that come out of like complex
interactions between the electrons and the positive ions that they're
embedded in. And you know, not all these things last
for that long, you know, like Cooper pairs don't tend
to last for very long in super conducting materials, but
you can still apply the mathematics to them for as
(33:19):
long as they do live. And so do you call
that carrying another particle? So a quasi particle with a particle,
you can group them into a quasi particle too, Yeah, exactly.
So it's just like you were saying before, it's a
quasi particle made out of a particle, and a quasi
particle seems really meta. It's pretty meta, and it lets
us explore sort of the theoretical space for particles that
(33:40):
we don't see in terms of fundamental particles. Like we
talked on the podcast recently about whether neutrinos are their
own anti particle. And this is a special kind of
particle called a myrona for me in invented by an
Italian guy and toward a marna. And we've never seen
a myrona for meon Like, we don't know if neutrinos
are their own antiparticles. We're curious about it. We've never
(34:01):
seen it. But in quasi particles, we've seen quasi particles
that have this property that are their own anti particles,
where two of them when they bump into each other,
they annihilate, And so we sort of have seen the
mathematics of my ironic formons work on the level of
quasi particles, even if we haven't seen it work for
(34:21):
fundamental particles. And that tells you that, okay, well the
math is right. If those particles exist, they're out there,
we know what they would do. All right. Well, let's
get into the question of maybe the more philosophical question,
which is our quasi particles real? Are they just kind
of like phenomenon or do you think there's something fundamental
(34:42):
about them in the universe. We don't know if they're real,
or I guess we don't know if they're fundamental. We
don't know if anything is real, right, I mean, quasi
particles are a mathematical way to describe, like some information,
some labels, moving through a material. You could say the
same thing about particles, except there the material is not
like a solid or crystal. It's a quantum field, right. Particles.
(35:06):
We say this on the podcast all the time. Particles
are just excited little blobs of energy moving through a
quantum field. And we had a listener question recently, like
why do we have particles at all? And we said
that there there's like a minimum energy that quantum fields
can store, and that energy moves around and that's what
we think of as a part of it. So maybe
this whole particle idea is a human idea. It's just
(35:28):
our interpretation of a localized packet of energy, and we
apply that to what we call fundamental particles that we
don't know if they're fundamental, and also to sort of
larger groupings of things. So I find that argument kind
of persuasive that there really is nothing fundamental interesting, Like
maybe everything should just be called an energy on or
something like that, you know what I mean, Like everything,
(35:50):
like everything is just an excitation, Like everything is just
a lip in something else. Yeah, exactly. And maybe it's
not fair to have a distinction between particles and quasi particles.
That all particles, right um, they're all really the same.
It's just a question of like what are you wiggling?
Are you wiggling some other matter or you're wiggling a
quantum field. What it makes me think is like what
(36:11):
if quantum fields are actually made out of other little things?
You know what I mean? Like maybe but we just
can't see them. Yes, very likely they are because our
description of the universe in terms of quantum fields doesn't
really work at some levels. So a lot of open
questions we've talked about, you know, why do we have
so many of these fields? Why do we have like
(36:31):
several different kinds of forces, each of their own kind
of field. Are they all just part of one field?
Is there even really a field? Or is it an
emergent property of something deeper? And so I think that
you know, this era of particle physics, where we talk
about the universe in terms of particles and the fields
that they wiggle on, this is probably a temporary phase
in the sort of the longer history of physics, before
(36:52):
we dig in and we find some other concept, right,
because you know, the concept of particle is only like
a hundred and something years old. We could very well
come up with a new mathematical concept that the universe
is based out of. That's what string theory is the onion,
I'm telling you man, you heard it here first, folks.
That's right. It has layers. Is a theory that has
(37:13):
layers and makes you cry. It makes me cry the
more I hear about it, exactly, but slice into it. Yeah,
but you know what I mean like like maybe what
we think of as fundamental right now, like quirks and
the electron, maybe they're just like holes in the medium
of other stuff, smaller particles. Yeah. Absolutely, and everything that
we have, all these ideas, we have, this understanding we
(37:35):
have about the universe. These are just ideas in our
head to describe the experiments that we do and the
observations we make. We don't know that any of it
is like true in any sense. It's just useful and
seems to work, and it seems awfully true because it
really really works. We're gonna do an episode next week
about like the super high precision of the predictions, Like
(37:55):
the mathematics of these fields and these particles gets things
right on to like twelve fifteen decimal places. So it
seems really true, but we don't know that it is.
I I remember having this moment in college when I
was learning about quantum mechanics and seeing one of these
calculations where the calculation was done and the experiment was
done and the two agreed to like fifteen decimal places,
(38:18):
and I remember thinking, Wow, it's like this theory is
not just good, it's like what the universe is doing
and that could be true. It could be that the
universe has field and it's doing these field calculations to
describe how particles move. But it could also be that
that's totally wrong and it's just an emergent picture or
something much simpler, much deeper, that hopefully we'll stumble across soon.
(38:39):
Like maybe it's just a big coincidence. It could just
be And it could be, you know that the way
that we think about it, and who happened to be
around when we started thinking about it, and the ideas
that they had. If you ran like history twice or
ten times or fifteen times, you might get very different
mathematics and therefore very different sort of like intellectual notions
about how to organize our knowledge about the universe. And
(39:00):
that's really what a particle is. It's a human organization
of our knowledge of the universe. So you might have
come up with a different idea and science could have
followed a very different path. Well, Daniel, I feel definitely
a few excitans about the whole endeavor and to learning
more about this. It is kind of a cool way
to so to see the universe, like maybe the universe
(39:23):
we see when we look at the stars, and when
we look at ourselves in the mirror, you know, we're
all just kind of like little packets of excitability, of
little pockets of energy. It's just kind of rippling around. Yeah,
and it's fun to think that you can explore that
on the micro micro micro level. You can break yourself
up and and think about the smaller and smaller particles.
But it also works the other direction. You can build
(39:43):
up from there and think of like particles at another
level and a meta level, and it's still kind of works.
And then that's sort of amazing. That tells you that
you know, this concept of like a packet of energy
or packet of excitation moving around, maybe that is something
real and true in the universe. Interesting, Like everyone listening
to this podcast is you on, A person on a person,
(40:05):
a person on Daniel, It's already there. I bet they're
hoping that you will move on from this jew All right,
let's let's phone it in and phone on it in
and wrap it up. Time to go on. All right, Well,
thanks for joining us. We hope you enjoyed that discussion,
that that quasi discussion and maybe look at the universe
in a slightly a different way and Thanks to everybody
(40:26):
for writing in with your curiosity. We love hearing what
you are curious about. The goal of our podcast is
to bring you to the forefront of science, and so
when you hear something talked about you don't understand, send
it to us. We will break it down for you.
We will explain it to you in a way that
makes sense and hopefully makes you giggle on See you
next time. Thanks for listening, and remember that Daniel and
(40:54):
Jorge Explain the Universe is a production of my Heart Radio.
For more podcast from my Heart Radio and visit the
I Heart Radio, Apple Apple Podcasts, or wherever you listen
to your favorite shows. H
Hey, Daniel, what am I made out of? You're made
of particles? Uh? And my lunch particles? What about the sun?
Also particles? Okay? Now what are all of those particles
made out of? Probably smaller particles, says it. Particles all
the way down. Is there anything that's not a particle?
You're asking a particle physicist, So what else do you
(00:29):
expect to hear? An actual particle of explanation? Well, I
think this podcast is basically a particle. Is it made
out of? Explain eons? Bad punions? Bad? I had a
bad punion last week. Didn't go over well? Hi or
(01:00):
handmade cartoonists and the creator of PhD Comics. Hi, I'm Daniel.
I'm a real particle physicist, not a quasi particle physicist.
Welcome to our podcast, Daniel and Jorge Quasi Explain the Universe,
a real production of Radio That's Right, in which we
talk about all the things that are real, all the
things that are crazy, and all the things that are imagined,
and our interpretation of all of them. We break them
(01:23):
down for you and try to give you an understanding
of what's going on out there and how scientists are
thinking about it all the mysteries of the universe, all
the unanswered questions, and all the amazing facts that we
have learned. We bring it all to you with a
pun or two. It's right, all of the things that
are out there and all the things that might also
be out there that scientists are not sure actually exist
(01:44):
or are even real, even some things that could be
semi real. Isn't that a weird term, Daniel, semi real
almost real? It's semi weird. Yeah. Yeah, Well, you know
there's a whole rabbit hole we could get down into
there by like what is real even mean? Man? But
I don't think we've smoked enough banana pee is yet
today to get there, or like our rabbits even real.
That's another rabbit hole in itself. And why are they
(02:05):
chasing bananas down rabbit holes? Like that never made any sense. Yeah,
So everything's a particle. It seems like, you know, all
matter in the universe, And so it kind of begs
the question like what are particles themselves made out of
and what is not made out of particles? And could
there be something else that's not a particle but still
make up matter? Yeah, And particles are sort of an
idea that we have. I mean, we look out in
(02:27):
the universe and we break things up and we see
them as smaller and smaller bits, and then we have
this notion that the smallest piece might be this dot.
But the whole concept of a particle is a little
bit fuzzy. We've talked on the podcast about the discovery
of particles. Whate really means to be a particle? You know,
the first particle ever discovered was the electron. It was
really just the identification of a point in space that
(02:49):
where you had charge and mass at the same time,
like this little cluster of quantum labels. And since then
we've added stuff to it. You know, particles can have spin,
that can have magnetic moments, that can do all sorts
of crazy stuff. But still this concept of like what
is a particle what does it mean remains a little
bit fuzzy. You know, they don't have any volume, They
do all sorts of weird things. Sometimes they act like waves,
(03:12):
and so it begs the question of like our particles
real or they're just something sort of in our mind?
And can we apply this notion of particles to other things? Also, now, Daniel,
as a disclaimer, we we should say that you are
a particle physicist, so you might not be entirely neutral
on this subject, might be a little biased. Or I'm
an expert, right, so you should you should listen carefully
(03:32):
to my thoughts about it, because I'm well informed. No,
it's certainly true, and I like to think of the
universe in terms of particles. I'd like to think that
the universe can be explained in terms of a bunch
of little microscopic things, that everything is really just an
emergent phenomena of the microscopic I guess a particle physicists,
everything looks like a party, just like I've heard astronomers say,
we're all made out of stars. I'm like, mmmm, that's convenient. Yeah,
(03:57):
And it's sort of a question of scale. Even astronomers
some times they treat like the whole sun as a particle.
You know, when you're doing your gravitational calculations about you know,
moving a planet around a star, you don't really care
about how big the star is. You're so far from
it that you can effectively treat the whole star as
if it was a point mass at the center of
mass of the star. And that's basically calling it a particle.
(04:19):
It's saying, I don't care about any other details. I'm
just gonna put it as a point. So it's a
very powerful concept, even if you're not gainfully employed in
the field. Right, And generally speaking, it just kind of
means like a packet of stuff, right, Yeah, it's sort
of like a little cluster of labels. You know, you
can put a mass on and a spin on it,
you know, other kind of quantum labels. But yeah, it's
like a little cluster of labels. Yeah, like a whole
(04:41):
bunch of little labels moving around together. Yeah. Like we've
talked about how the new trino, you know, it carries
a weak label but doesn't carry one for the strong force,
and if photons don't carry any mass, but they do
carry information about electromagnetic fields. And so to me, I
think about these things having their little dots in space
that have labels on them. And so there's this concept
in physics called a quasi particle. Is it quasi or
(05:04):
quasi part I'm quasi sure that it's quasi particle. Obviously
quasi experts in vocabulary here and pronunciation. If we're wrong,
we're only quasi wrong. It's better than being semi wrong,
I guess or pseudo wrong, pseudo experts. There you go.
And this came to us from listeners actually who had
a question about what these things are. Listeners, Linda Campbell,
(05:26):
Nick Beatrice, Jack Case, Tim Davis, they all wrote to
us asking what a quasi particle is. That's right. If
you have a question about something you'd like us to
talk about, right to us, because we will actually answer
your email and sometimes even do a podcast on it.
And these folks had seen articles about quasi particles and
(05:49):
asked us to explain it. What is a quasi particle?
What does it mean? And have we gone too far
with this concept of particles? Impossible? You can't have enough particles,
said to a particle physicist, you can't have too many particles.
I mean, it's such a nice idea. Now we don't know, right,
like we don't know if particles go on forever, if
you can get down to the smallest possible particle, or
if you get small enough particles doesn't really work and
(06:11):
you need something else, like you know, pixels of space
or little strings or something else. But so far, it's
a very nice idea to explain the world around us,
Like if you have a hammer, everything looks like a nail.
If you have a particle collider, everything looks like a particle. Yeah.
And if particles have worked, then you extend the idea.
You're like, well, let's see if this would also help
us understand this other problem. And we do that in
(06:32):
physics and in math all the time. We take strategies
from one field and we apply them somewhere else to
see if we can make connections. You know, one of
Newton's greatest leaps forward conceptually was understanding that the same
rules applied in the heavens and on Earth. And that's
all we're trying to do. We're trying to use the
concept we discovered in particle physics, the group theory, the symmetry,
the conservation laws, and apply them other places. Yes, Daniel,
(06:54):
but what is heaven made out of particles? Particles, angel ons, halons?
There you go? Um. So, as usually, we were wondering
how many people out there actually had heard of this
concept or knew what it was. So Daniel went out
there into the wilds of the Internet to ask this
question and get people's responses. So before you listen to
(07:15):
these answers, think about it. For a second. Have you
heard of quasi particles and if somebody asked you, what
would you say. Here's what people had to say. Sounds
like something that has some of the properties of particles,
but perhaps doesn't satisfy all of the conditions. Either that
or some guy named quasi came up with a new particle,
probably something that wants to trick you that it's a particle,
(07:39):
and it's not guess that there are particles with more
than one. Quasi particles are virtual particles that don't follow
the rules. Crazy particles, particles which are created in the
vacuum because of the background energy of space that's sort
of there and they're not there. Maybe how that's how
(08:01):
that's something? Is that like a virtual particle or maybe
something that we've seen in the data when we've been
looking for particles that we can't quite explain. Particles have mass,
and quasi particles maybe doing maybe don't. Maybe they go
through a filter in the universe. Something that's almost a
(08:22):
particle or something very similar to one. I'm not a
native speaker and I had to look quasi in dictionary.
It can semi so coarse particle is semi particle, Quasi
means something that looks like something else. So I'm assuming
the quasi particle is a particle that looks like a
(08:45):
particle but really isn't. I would say a quasi particle
is a particle that may appear to be real, but
actually it's not. There was something super tiny. Well those
are some pretty good guesses. Yeah, I like the person
who looked it up in a dictionary. I'm like, I
know there's some rules here. You're not supposed to look
anything up or google anything, but you know, not being
a native speaker, I'll forgive them, right, Maybe there's just
(09:07):
quasi rules. So yeah, let's jump right into a daniel um.
What is a quasi particle. So a quasi particle is
called a quasi particle because it's something that behaves like
a particle, has some of the same properties that we
typically use to describe particles, like it's persistent, you know,
it sticks around. It's quantized. You know you can have
(09:27):
one or two without one and a half. Usually they're discreet,
but it's not actually fundamental. It's not like something that
is the building block of the universe. It's not a
ripple in the quantum field. It's usually like an excited
state of some macroscopic solid. It's something that behaves like
a particle, but it's not actually a particle. So does
that include like the protons and neutrons, you know, the
(09:51):
behavior like particles, but they're actually made out of smaller
particles inside. Is that kind of what you mean or
is it are you talking more like bigger scale? We're
talking bigger scale, I mean, and you could argue you
that protels and neutrons are not particles because they're not
fundamental and they don't have their own quantum fields, and
so in that sense, they really are an emergent phenomenon.
And we can get into that later on. I think
that's a fascinating question. But I think typically people think
(10:13):
when they talk about emergent phenomenon, they think about sort
of a larger scale. You know, imagine like you have
a glass of water in front of you and it
has that's sparkling. Water has bubbles. You can see those
bubble sort of move up through the water, and they
move sort of the way a particle does. They hold
their shape, they're consistent, you know, they're coherent. They move
through the water the same way a particle does. You
(10:34):
can apply a lot of the same mathematics and understanding
intuition that you apply to particles to that bubble in
the water, even though nobody thinks that bubbles are a
fundamental unit of the universe or that there's like a
quantum bubble fielding as a manifestation of maybe quarks are
made out of bubbles that we have yet discovered. Yeah,
it's bubble theory, you know, the same way you can
(10:55):
look at like the ocean and you can see a
wave moving through it. A wave is not a fundamental
proper of the universe. It's an emergent phenomena of all
these thousands and millions and trillions of particles all moving together.
But mathematically it's much more convenient to talk about the
wave than to track all the little particles that make
it up. So quasity particles in the same way, but
not really that big a scale on the scale, like
(11:17):
bubbles and waves, but you know, like excited states of solids,
like wiggles that pass through solids, or rotations of things
that move in a coherent way and and sort of
keep their identity as they pass through a solid, right
like sound waves. Also could a sound wave like a
shout or a screen be considered a quasi part of Yes,
sound waves like vibrations. Basically, if you break them down,
(11:39):
you can go down to like the quantum. The smallest
possible sound wave is like the vibration of a single
particle that is a quasi particle. It's called a phone on.
A phone on is like the I did not just
make that up. You can phone anybody and ask them
about it. It's seriously then, no, it's sort of like
(12:00):
a you know, it's a more general sense of what
a particle is. And here you have like a single
particle might be vibrating, and then it passes that vibration
off to the next particle and to the next particle
and the next thing. It's yeah, and it's quantized, right,
because these particles that are vibrating the atoms or whatever
in your lattice. You know, say, for example, I knock
on the desk in front of me, it sends sound
(12:22):
waves to the desk, or if I speak through the air.
Then those particles, the ones that are doing the wiggling,
their quantum particles. They have quantum states. It's like a
minimum amount of vibration that they can have. And so
if you have that minimum amount of vibration, they could
pass to the next one and pass to the next one.
And that's what keeps it like a coherent thing can't
just disperse out into infinitely smaller things. It sticks around
(12:45):
because of these quantum minimum They're almost like packets of stuff.
And it's sort of a mental game you can play
with yourself, like what's a particle and what's a quasi particle?
You know. Another great and classical example of a quasi
particle is the absence of a particle. What. Yeah, Like
you ever play that game where you have like a
bunch of tiles and there's one open slot and you
(13:07):
have to slide the tiles around, like get them in
the right order, like the little puzzles. Yeah, those little puzzles. Well,
you can think about it like as the motion of
a bunch of tiles, or you can think about it
as the motion of a hole of a gap. Right,
that gap is sort of moving through the puzzle. You're
moving that gap around, so that little hole is like
a particle. That little hole is sort of like another tile, right,
(13:28):
And so in the same way, if you have like
a whole bunch of electrons, you can think about one
missing electron moving around like they have a ten slots
for electrons, but only nine electrons, so there's one hole, right,
and then if all the electrons move over, then the
whole moves the opposite way, right, the opposite way precisely.
So you can either think of it as moving like
(13:49):
every single electron over one slot, or you can just
think of it as the whole moving over one in
the other direction. There's two equivalent ways to think about it,
but one of them is simpler because you've abstracted away
a lot of complications, so you can think about it
and just this one blob in the same way that
like watching a bubble rise through water is simpler than
thinking about all the billions of little particles that are
(14:11):
making that happen. So you sort of like abstracted away
some stuff so you can apply your particle brain to
this new kind of thing. I see, you just kind
of blew my mind a little bit. Yeah, just to
think of that. Bubbles are not actually a thing. They're
just like water, molic is moving out of the way.
That's a bubble, Yeah, exactly, They're just getting pushed out
of the way by that air. But the arrangement is
(14:32):
sort of static. There's like a minimum size to those bubbles,
right because of surface tension or whatever. The bubbles can't
just break up into infinitely small bubbles and that's why
they stick around right until they eventually they pop. And
in the same way, like electrons can't split in half,
and so that's why you don't get these holes like
gradually filled in with partial electrons. Now, this sounds kind
of very macro like, you know, we're talking about bubbles
(14:54):
and ways. Now, is this something that you use a
particle physics deals with or is it more like a
bigger things physics. Neither. Actually, it's not something that I
deal with because I usually deal with actual particles, real particles,
you know, particles that are excitations of quantum fields. But
it's also not something that happens on the macro scale.
Usually it's most often on the micro scale. So it's
(15:16):
something in the adjacent field of condensed matter physics. People
who build like weird materials and you know, super fluidity
and think about super conductivity. I mean, another great example
of a quasi particle are pairs of electrons that cause
super conductivity. You know, one reason that metals have a
hard time being super conductive is because electrons are fermions.
(15:37):
They don't like to be in the lowest state together
with another one. But in super conducting materials, we did
a whole podcast episode about that, electrons like to group
together into pairs. They're called Cooper pairs, and they're pushed
together into these pairs and together they're actually bosons. They
have the opposite rules from fermions, and so they can
cool down and all occupy the same state and flow
(15:59):
smoothly over each other. So a Cooper pair is like
a pair of electrons sort of acting like a particle.
And so that's another example of a quaty particle. They're
often at this micro level. I guess the common thread
is that they maintain some sort of quantum property, right,
like a dust particle. Physics wouldn't call a quasi particle, right,
It has to sort of maintain that quantuminez feeling about it. Yeah,
(16:21):
And you know, you could probably argue that anything as
a quasi particle, but I would say that it should
be persistent, and it should be quantized, and it should
be discreete. So many Q words quanti quasi qualitative, quantity
of particles exactly and so it's fun. It's like an extrapolation.
And this is always really fascinating in science when you
(16:41):
can see something in the world and then apply those
same ideas somewhere else and gain some insight because it
kind of works, you know, it helps you. It simplifies
the problems so you can see the larger dynamics and
gives you an insight into what's going on. It lets
you use your intuition from somewhere else. And that's what
science is all about. It's not about figuring out the
rules for a and there for being there for see,
we want rules that explain everything. We want rules to
(17:03):
tie everything together. And so yeah, if you have a
hammer and you've hit a bunch of nails successfully, you're
gonna go around and hit everything else with that hammer
until they look like nails, until they break apart into particles.
Very convenient. It all works, See, it all works. All right,
let's get into what are some examples, some fun examples
of quasi particles, and then let's talk about whether they
(17:23):
or not they're actually real. But first let's take a
quick break. Al Right, I know we're quasi talking about
quasi particles. I'm really talking about real particles. And even
(17:46):
this podcast is sort of a quasi particle, right, I guess,
because you know, it sort of exists as electrons moving,
which are particles, and it gets toward as information and
it gets turned into sound ways, which are sort of
quasi particles too. That's right. This part cast cannot be
broken up into smaller pieces, and so it's therefore a
quantized podcast and cannot disperse the universe and must be
(18:07):
accepted into your brain. In total. It's both good and
bad at the same time. You're welcome, of course, to
listen to the podcast in five minute increments or twelve
minute increments or five all at once, so do with
as you please, of course. Oh my goodness. All right, well,
what are some examples of quasi particles, Like we talked
a little bit about phonons being like sound waves particles. Yeah,
(18:28):
Phonons are vibrations, they're like the quantum of sound waves,
are like the minimum component of sound waves. All sound
waves in a solid are built out of phonons, and
so the smallest possible sound wave you can have in
a solid is one phone on and you know, it's
just like energy moving through the solid. This atom vibrating
in a lattice, and then the next one vibrates and
(18:49):
the next one vibrates, and so you can think of
that as the phone on moving through. And I think
phone on is pretty cool word to ye. It makes
me think of like some sort of like Star Trek gun,
like you know, set your phone on, blasters on, wiggle um,
I don't know, it's it's very reminiscent for me of
phoning it in. I feel like physicists phoned it in
(19:11):
when they came up with this name. They're like, what
do we call a sound wave particle? I know, a
phone on and I think it's awesome. Yeah, and then
all the other quasi particles all have sort of similar names.
You know, the kind of thing that's getting wiggled or
you know, moved through and then on at the end
of is it related to sort of like the medium
on which these things propagated or move around in, Because
(19:34):
I feel like a sound wave is quantized because the
underlying thing that they're on is quantized. So it's at
some point, you know, you can't make a smaller sound
wave because run into particle, that's right, because those particles
have quantized energy levels. Like, they can't wiggle at half
of their energy level. They can wiggle at one energy
level or two or three, but there's a minimum amount
(19:56):
of wiggle and that's why it's quantized. You know. That's why,
for example, they can't accept a photon of arbitrary energy.
They're resonant frequencies frequencies that solids like to accept photons
because it helps them move exactly one energy level up.
And also that's why solids give off light at certain frequencies,
because you know that's the resonant frequencies for that gas.
(20:17):
For example, I can excite up by absorbing a photon
and excite down by giving off that photon. And when
absorbs the photon, like, where does that energy go? It
goes into a phone on? Right. A phonon is the
energy moving through the gas. So photons get turned into phonons, right. Well,
that's fun to say. And so what are some other
(20:37):
examples of quasi particles? Well, basically every quantum property that
a particle can have when you put it in a lattice,
you can think about that property moving through the ladder.
What is like a like a grid of particles? Yeah,
every solid you can think of is like a grid
of particles, like a three D like a lego set
of particles put together. And so they're all back together,
(20:58):
back together. Each one is touching the one above and
below it into its left, into its right, forwards and backwards,
and they're sort of tied together by these bonds. And
that's what makes a solid, right, it's sort of like
a loose crystal. And so they're in this lattice so
they can pass information. Right, It's like if you're in
a crowd of people and everybody's whispering into their neighbor's ear,
you can pass information through the crowd, and so that
(21:19):
same way, like that's how these bonons get passed through
the crowd. But you can do it also with other
quantum properties like the particle spin. You said we could
do it with holes, but you can also do it
with like quantum properties like charge and mass and things
like that. That's a good point. I mean, for charge,
it's sort of holes, right. Holes essentially is the moving
of charge around, but they're the actual particle moves over,
(21:41):
like the electrons have to move over. You can't pass
charge from one particle to another the way you can
pass energy and electron moves from here or there, it
moves the charge with it, creating sort of like a
like a hole in the charge. Yeah, so you can
have quasi particles in like a particle gas right with
the electrons are free to move around. Then the apps
and of a particle is a quasi particle that whole.
(22:02):
But also in a lattice, you can have quasi particles
like the phonon, but also things like the magnon, which
is the the quantum of particle spin that helps create
the magnetic field that metals can have. For example. Now
that one does sound like a transformer, I have to say,
which I'm all for. Waits. A particle spin can also
(22:24):
move around like a wave. How does that work, Like
the orientation of it or what does that mean? Yeah,
the orientation of it. Remember, the particle spin is quantized.
So for example, an electron can be spin up or
spin down. So say you have a bunch of electrons
that are all spin down except for one that's spin up.
Then it can sort of pass that spin to the
next electron making its spin up, And it can pass
(22:45):
that spin to the next electron it can make its
spin up, so the spin up nous can move through
this sort of grid of electrons, and you can think
of that it's like, oh, well, I got a bunch
of electrons summer spin up and summer spin down. Or
you can think of it like, oh, I have a
magnon that's moving through a sea of electrons because like
one particle will give it's been to the next particle,
(23:08):
or or just from the gap of it. Yeah, they
can transfer because they couple to each other a little bit.
You know, Electrons talk to each other, they bounce around,
they share energy, they interact, and spin is conserved. So
you can't just like have them all be spin up.
If they're all spin down except for one, then you
have to have one electron spin up. It's just a
question of which one. And because it's quanti as, you
can't have like half spin up and a third spin up.
(23:31):
You need to pass the whole thing over from electron
to electron. And so the magnon moves around. Is it
like the potato in a game of pot potato? Exactly exactly,
But I'm not sure. Maybe the electrons want to be
spin up, right, Maybe it's like, hey, give me that
hot potato. No, give me that hot potato. I can't
speak for the electrons. We should just rename the game
to magnons or quasi potatoes, and then every time you
(23:55):
want to play with your four year olds, you have
to explain to them quasi particles, and then you know
they're not interested in anymore, and then nobody wants to play.
But these are actually really cool and they have other
applications and particle physics, like if you search for magnons,
you can be sensitive to really small effects. Like if
you get a field of particles and they're really quiet,
then you can look for magnons as evidence of like
(24:15):
maybe dark matter has come through and hit one of
these electrons and given it a spin, and so you
can try to measure these things using very very sensitive
magnetometers because remember the spin of the particle effects it's
magnetic field, and so that's why we call it a magnal.
It all goes back to dark matter, doesn't it. In
the end, it's only exciting if it can help you
find dark matter. I guess maybe right, because it motivates
(24:39):
why you want to study it. Maybe it's a big mystery. Yeah,
But here it's just like this is a cool idea
and it gives us a new way to look for
something really cool, and it's an example of why it
is good to use like particle physics ideas in other areas,
Like you can get this inside into condensed matter and
how spin moves around in the lattice of electrons, and
then that gives you an idea for how to look
(24:59):
for some thing else cool and news. So you know,
it's sort of like refreshes you creatively intellectually to like
look at something from a new perspective. So is the
idea then that, like if I have a whole bunch
of electrons and they're just hanging out and suddenly there's
like a potato in the middle, they're like, You're like,
must have been dark matter that gave us that potato, right,
or you know spin obviously, But is it kind of
(25:20):
like that, Like if there's suddenly a potato in the middle,
you've gotta wonder where that potato came from. Yeah, exactly,
And eventually one dark matter experiment will have to be
called potato based on this podcast, Yeah, physics ordinary what's
the right acronym there? Transfer Well, while you work on that,
you know, these things actually do have special power to
discover dark matter because the kind of dark matter experiments
(25:41):
we have right now are mostly waiting for dark matter
to bump into the nucleus of the atom, you know,
the big heavy protons and neutrons, and we see that
kind of nuclear recoil, You see that getting kicked, and
that requires kind of heavy dark matter, because you've got
to be big enough to like give it a kick.
The dark matter is really really whispy, then won't move
those neutrons and protons even if it does bump into them.
(26:03):
But these magnon detectors could be much more powerful as
a way to search for a very very light, very
low mass dark matter. And since we haven't found dark
matter at the higher masses where we've looked for it,
it's quite exciting to say, oh, look, we can build
new detectors that might be sensitive to even whispy or
dark matter. Because electrons are more sensitive than protons and neutrons,
(26:25):
well they're just lighter and so they're easier to kick. Right,
if you are a very light particle, then you're gonna
have a bigger effect bumping into an electron. Then you
are bumping into a proton or neutron, which is like
you know, a boulder in comparison. So if dark matter
can interact with electrons, then you would see it in
a very kind of maybe bigger way if you look
for these quantum spin quasi particles. Yeah, if you look
(26:50):
for Magnon's exactly. I feel like you don't want to say.
Magna is such a fun word. Yeah, Magnon, Magnon. And
there are lots of other kinds of quasi particles. You know,
there are polarns. This is when electrons interact with the
polarization of ions. Wait, I just came up with a joke, Daniel.
If you make this project, if you set up this experiment,
(27:10):
you should call it the Magnon Particle Interface Maximon Particle
Infation mp I, No Magnan p I. The ready for
prime time. Everybody has to unbutton their shirt two buttons
to work on this experiment. Yeah, and have a month.
I'll start growing it. Then there's the like there are
rotons if you have like a fluid rot If you
(27:32):
have a fluid, then you can get like vortices in it, right,
you can like little whirlpools and the sort of the
minimum amount of vortex that you can get turns out
to be quantized because of how these particles can spin,
and so that's what a roton is. It's like the
minimum quantum of vortices, I guess, because the medium again
is quantized, so you know, a little like vortices also
(27:55):
have to quantize because there's a minimum size to these particles. Yeah,
and they have energy levels, and just the same way
that phonons exist because solids and allattics have energy levels
to their vibrations. Fluids also have energy levels, and these
particles inside them, these vortices have sort of a minimum
energy level, and so that's that's where you get routons,
and then you get other really weird things. And you
(28:15):
can apply this really broadly, and it's been like an
explosion of different kinds of quasi particles people have sort
of created or or conceived of. You know, they even
have like weird two dimensional quasi particles. All right, let's
get into the rest of these quasi examples of quasi particles,
and then let's get into whether or not they're actually real,
(28:35):
like philosophically, could we call them real things? And how
does that maybe put into question the particles and we're
being out of But first let's take another quick break,
(28:57):
all right. I know, so we covered the phone on
the magnan and the rotons. What other ons of people
sort of discovered or study. One of my favorites is
this weird one. It's an excitation in plasma. So plasma
is like you take gas and you heat it up
so much that the electrons and the nucleus separate, right,
the electron becomes free, and you have like a charged
(29:19):
gas and this is really hot and nasty stuff, and
it's you know, it's what the sun is made out of,
and it's what we used to try to do fusion.
And sometimes you can get it acting in sort of
like sheets. You can get these like sheets of plasma
layering on top of each other because these things have
charges and so like you can get like a negatively
charged sheet and then a positively charged sheet, and then
(29:40):
a negatively charged sheet sort of like stack up on
top of each other, and weird ripples passed through these
two d sheets of plasma. And these things are called plasma.
That would be a good one, but no, they're called
for reasons I don't understand. They're called an eons but
(30:01):
like a n y on and you know, It makes
me wonder, like, how did they come up with that name?
Like maybe all the other as were taken and somebody said,
is there anything left ding oh anyon nons or something, Daniel,
what do you call a quasi particle made out of
quasi particles? A quasi quasi particle an on? Of course, Man,
(30:24):
I walked into all these terrible jigs you are, I
am just firing off the quasi pat chokes here. But
there's some really cool mathematical features of these things, Like
these anions they actually act like two dimensional particles. It's
like a mathematical system that we don't see in reality.
You know, our universe is in three dimensions, so our
particles move in three dimensions, and there's different mathematics that
(30:46):
apply to two dimensions, the surface of things and the
surface area of things, and how things diffuse, you know,
instead of going like one over our square, that goes
like one over our And these anions actually exhibit those
mathematical properties as if they were too d particles. And
that's really kind of cool. That's just like test out
these mathematics in real life interesting because then then you
(31:08):
can have like different kinds of physics, right like you
can have too D physics, which could be totally different. Yeah,
it is totally different, and it's fascinating to see it.
And like, of course it's made out of three D things,
so it's not really two D, but it's sort of
like a physical simulation of two D, which is really
pretty cool because you see these effects happening, but sort
of you know, quasi, there's like on the meta level,
(31:29):
you're like abstracted it out. And in this interpretation of
these plasma wiggles where I call these an eons and
treat them like particles that I see, that follows exactly
the math you would expect for actual two D particles,
and that's pretty cool. Like you can describe them with
wave functions even though they're they're not like they're just
gaps in other wave functions. Yeah, exactly, exactly. You can
(31:51):
describe them with wave functions and all the mathematics we
use for particle physics, but in two D. So that's
pretty awesome. All right, what are some other cool quasi particles?
I think maybe the That's what I'm excited about is
the exciton. There's actually a part of the exciton. Yeah,
and it's not like the quantum unit of Daniel's enthusiasm
(32:12):
for science. You know, it's has a minimum are you
saying there's a minimum excitability threshold always above zero? It's
always above zero. And this is when you get an electron,
which is a particle, you know, and a whole. So
a hole is already a quasi particle, right, it's the
absence of an electron. It's where it's a gap where
you might expect an electron. But sometimes electrons and holes
(32:36):
can interact with each other because that a whole is
in effect positively charged, right, The absence of a negative
charge is like a positive charge, and so the electron
and the whole can interact and they can actually form
these bound states. One electron will will drag a hole
behind it, and so they're sort of moving together. The
electron would drag the whole, Yeah, the electron will drag
(32:58):
the hole behind it, because you know, whole is sort
of like the absence of an electron. And you know,
these are all things that come out of like complex
interactions between the electrons and the positive ions that they're
embedded in. And you know, not all these things last
for that long, you know, like Cooper pairs don't tend
to last for very long in super conducting materials, but
you can still apply the mathematics to them for as
(33:19):
long as they do live. And so do you call
that carrying another particle? So a quasi particle with a particle,
you can group them into a quasi particle too, Yeah, exactly.
So it's just like you were saying before, it's a
quasi particle made out of a particle, and a quasi
particle seems really meta. It's pretty meta, and it lets
us explore sort of the theoretical space for particles that
(33:40):
we don't see in terms of fundamental particles. Like we
talked on the podcast recently about whether neutrinos are their
own anti particle. And this is a special kind of
particle called a myrona for me in invented by an
Italian guy and toward a marna. And we've never seen
a myrona for meon Like, we don't know if neutrinos
are their own antiparticles. We're curious about it. We've never
(34:01):
seen it. But in quasi particles, we've seen quasi particles
that have this property that are their own anti particles,
where two of them when they bump into each other,
they annihilate, And so we sort of have seen the
mathematics of my ironic formons work on the level of
quasi particles, even if we haven't seen it work for
(34:21):
fundamental particles. And that tells you that, okay, well the
math is right. If those particles exist, they're out there,
we know what they would do. All right. Well, let's
get into the question of maybe the more philosophical question,
which is our quasi particles real? Are they just kind
of like phenomenon or do you think there's something fundamental
(34:42):
about them in the universe. We don't know if they're real,
or I guess we don't know if they're fundamental. We
don't know if anything is real, right, I mean, quasi
particles are a mathematical way to describe, like some information,
some labels, moving through a material. You could say the
same thing about particles, except there the material is not
like a solid or crystal. It's a quantum field, right. Particles.
(35:06):
We say this on the podcast all the time. Particles
are just excited little blobs of energy moving through a
quantum field. And we had a listener question recently, like
why do we have particles at all? And we said
that there there's like a minimum energy that quantum fields
can store, and that energy moves around and that's what
we think of as a part of it. So maybe
this whole particle idea is a human idea. It's just
(35:28):
our interpretation of a localized packet of energy, and we
apply that to what we call fundamental particles that we
don't know if they're fundamental, and also to sort of
larger groupings of things. So I find that argument kind
of persuasive that there really is nothing fundamental interesting, Like
maybe everything should just be called an energy on or
something like that, you know what I mean, Like everything,
(35:50):
like everything is just an excitation, Like everything is just
a lip in something else. Yeah, exactly. And maybe it's
not fair to have a distinction between particles and quasi particles.
That all particles, right um, they're all really the same.
It's just a question of like what are you wiggling?
Are you wiggling some other matter or you're wiggling a
quantum field. What it makes me think is like what
(36:11):
if quantum fields are actually made out of other little things?
You know what I mean? Like maybe but we just
can't see them. Yes, very likely they are because our
description of the universe in terms of quantum fields doesn't
really work at some levels. So a lot of open
questions we've talked about, you know, why do we have
so many of these fields? Why do we have like
(36:31):
several different kinds of forces, each of their own kind
of field. Are they all just part of one field?
Is there even really a field? Or is it an
emergent property of something deeper? And so I think that
you know, this era of particle physics, where we talk
about the universe in terms of particles and the fields
that they wiggle on, this is probably a temporary phase
in the sort of the longer history of physics, before
(36:52):
we dig in and we find some other concept, right,
because you know, the concept of particle is only like
a hundred and something years old. We could very well
come up with a new mathematical concept that the universe
is based out of. That's what string theory is the onion,
I'm telling you man, you heard it here first, folks.
That's right. It has layers. Is a theory that has
(37:13):
layers and makes you cry. It makes me cry the
more I hear about it, exactly, but slice into it. Yeah,
but you know what I mean like like maybe what
we think of as fundamental right now, like quirks and
the electron, maybe they're just like holes in the medium
of other stuff, smaller particles. Yeah. Absolutely, and everything that
we have, all these ideas, we have, this understanding we
(37:35):
have about the universe. These are just ideas in our
head to describe the experiments that we do and the
observations we make. We don't know that any of it
is like true in any sense. It's just useful and
seems to work, and it seems awfully true because it
really really works. We're gonna do an episode next week
about like the super high precision of the predictions, Like
(37:55):
the mathematics of these fields and these particles gets things
right on to like twelve fifteen decimal places. So it
seems really true, but we don't know that it is.
I I remember having this moment in college when I
was learning about quantum mechanics and seeing one of these
calculations where the calculation was done and the experiment was
done and the two agreed to like fifteen decimal places,
(38:18):
and I remember thinking, Wow, it's like this theory is
not just good, it's like what the universe is doing
and that could be true. It could be that the
universe has field and it's doing these field calculations to
describe how particles move. But it could also be that
that's totally wrong and it's just an emergent picture or
something much simpler, much deeper, that hopefully we'll stumble across soon.
(38:39):
Like maybe it's just a big coincidence. It could just
be And it could be, you know that the way
that we think about it, and who happened to be
around when we started thinking about it, and the ideas
that they had. If you ran like history twice or
ten times or fifteen times, you might get very different
mathematics and therefore very different sort of like intellectual notions
about how to organize our knowledge about the universe. And
(39:00):
that's really what a particle is. It's a human organization
of our knowledge of the universe. So you might have
come up with a different idea and science could have
followed a very different path. Well, Daniel, I feel definitely
a few excitans about the whole endeavor and to learning
more about this. It is kind of a cool way
to so to see the universe, like maybe the universe
(39:23):
we see when we look at the stars, and when
we look at ourselves in the mirror, you know, we're
all just kind of like little packets of excitability, of
little pockets of energy. It's just kind of rippling around. Yeah,
and it's fun to think that you can explore that
on the micro micro micro level. You can break yourself
up and and think about the smaller and smaller particles.
But it also works the other direction. You can build
(39:43):
up from there and think of like particles at another
level and a meta level, and it's still kind of works.
And then that's sort of amazing. That tells you that
you know, this concept of like a packet of energy
or packet of excitation moving around, maybe that is something
real and true in the universe. Interesting, Like everyone listening
to this podcast is you on, A person on a person,
(40:05):
a person on Daniel, It's already there. I bet they're
hoping that you will move on from this jew All right,
let's let's phone it in and phone on it in
and wrap it up. Time to go on. All right, Well,
thanks for joining us. We hope you enjoyed that discussion,
that that quasi discussion and maybe look at the universe
in a slightly a different way and Thanks to everybody
(40:26):
for writing in with your curiosity. We love hearing what
you are curious about. The goal of our podcast is
to bring you to the forefront of science, and so
when you hear something talked about you don't understand, send
it to us. We will break it down for you.
We will explain it to you in a way that
makes sense and hopefully makes you giggle on See you
next time. Thanks for listening, and remember that Daniel and
(40:54):
Jorge Explain the Universe is a production of my Heart Radio.
For more podcast from my Heart Radio and visit the
I Heart Radio, Apple Apple Podcasts, or wherever you listen
to your favorite shows. H
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
Popular Podcasts
Stuff You Should Know
If you've ever wanted to know about champagne, satanism, the Stonewall Uprising, chaos theory, LSD, El Nino, true crime and Rosa Parks, then look no further. Josh and Chuck have you covered.
24/7 News: The Latest
The latest news in 4 minutes updated every hour, every day.
Crime Junkie
Does hearing about a true crime case always leave you scouring the internet for the truth behind the story? Dive into your next mystery with Crime Junkie. Every Monday, join your host Ashley Flowers as she unravels all the details of infamous and underreported true crime cases with her best friend Brit Prawat. From cold cases to missing persons and heroes in our community who seek justice, Crime Junkie is your destination for theories and stories you won’t hear anywhere else. Whether you're a seasoned true crime enthusiast or new to the genre, you'll find yourself on the edge of your seat awaiting a new episode every Monday. If you can never get enough true crime... Congratulations, you’ve found your people. Follow to join a community of Crime Junkies! Crime Junkie is presented by audiochuck Media Company.