Latest / Daniel and Kelly’s Extraordinary Universe / Can something be both a conductor and insulator?

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Can something be both a conductor and insulator? · Daniel and Kelly’s Extraordinary Universe

0:01
Speaker 1: Hi, it's Jorge and Daniel here. And this holiday season,
0:03
Speaker 1: if you're looking for a gift for yourself, for a friend,
0:06
Speaker 1: or for your family, why not get him the Gift
0:09
Speaker 1: of Answers about the Universe. To check out our new
0:11
Speaker 1: book Frequently Asked Questions about the Universe, you can find
0:14
Speaker 1: details at Universe f a Q dot com. Thanks for
0:18
Speaker 1: supporting the podcast. Happy holidays everyone, Y Daniel, I've got
0:31
Speaker 1: a really easy question for you. Oh, those the trickiest
0:34
Speaker 1: ones relaxed. I'm sure it'll be trivial, but here we go.
0:38
Speaker 1: What is a medal? Kind of depends on what temperature. Actually,
0:45
Speaker 1: it depends on whether you're an astronomer, a geophysicist, or
0:49
Speaker 1: a solid state physicist. But those are all physicists. You
0:52
Speaker 1: can't agree on what a medal is. No astronomers think
0:56
Speaker 1: that anything heavier than helium is a metal, and a
0:58
Speaker 1: solid state physicist thinks that anything that conducts electricity is
1:02
Speaker 1: a metal. Sounds like a little disaster. Don't get me
1:05
Speaker 1: started on how we define heavy metal, well, because you
1:09
Speaker 1: have to call the music physicists. It depends on the
1:13
Speaker 1: number of electric guitars involved. And how do you define
1:16
Speaker 1: space elevator? Music. Who do you call that? Hi, I'm
1:35
Speaker 1: or handmade cartoonists and the creator of PhD comics. Hi.
1:38
Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
1:40
Speaker 1: u C Irvine. And while I do want to ride
1:43
Speaker 1: in this space elevator, I've given no thought to what
1:45
Speaker 1: kind of music I want to hear as I'm writing
1:48
Speaker 1: up into space. I guess you want maybe um cosmologically
1:54
Speaker 1: classical music. Maybe maybe I want the opening music to
1:58
Speaker 1: our podcast, which is sort of space. You must want
2:00
Speaker 1: electric music, because you know that's a physical property. Yeah,
2:04
Speaker 1: I definitely don't want anything catastrophic or electromagnetic orchestra email music.
2:09
Speaker 1: But anyways, welcome for a podcast. Daniel and Jorge explain
2:12
Speaker 1: the university production of I Heart Radio. We are your
2:15
Speaker 1: mental musical accompaniment to our ride through the universe, elevating
2:20
Speaker 1: ourselves up into understanding the very nature of space and
2:25
Speaker 1: time and fields and particles. We go up and down
2:29
Speaker 1: while we examine what we do know and what we
2:31
Speaker 1: don't know about some of the deepest questions in the universe.
2:35
Speaker 1: Where did the universe come from? How is it gonna end?
2:38
Speaker 1: What does it all mean? Anyway? We talk about all
2:41
Speaker 1: of these things on the podcast, and we try to
2:42
Speaker 1: explain as much as we understand to you. Yeah, because
2:46
Speaker 1: it is a pretty musical universe. It's it sounds a
2:48
Speaker 1: little melodious and sometimes kind of chaotic and definitely epic.
2:53
Speaker 1: Definitely has an epic score for quality to the universe,
2:55
Speaker 1: that's right, And definitely kudos to the audio engineers for
2:58
Speaker 1: the universe. There's so many really rul sounds out there,
3:01
Speaker 1: and you just sit out there and listen. You hear
3:03
Speaker 1: all sorts of squishing and banging and squeaking, and wow,
3:06
Speaker 1: the universe is definitely chock full of cool special effects. Yeah,
3:09
Speaker 1: and we listen to the universe in all kinds of ways, right,
3:12
Speaker 1: Like there's sound waves, there's electromagnetic waves, there are gravitational waves.
3:16
Speaker 1: It's like the universe is a symphony using all kinds
3:19
Speaker 1: of instruments. Do you think any collection of sounds is
3:22
Speaker 1: a symphony? Like when you pick up your kids from
3:24
Speaker 1: daycare when they're two, you consider that sound a symphony
3:27
Speaker 1: tense screaming children? Depends on my mood, I guess, am
3:31
Speaker 1: I feeling like a cacophony of two year olds? Or
3:34
Speaker 1: would some peace and quiet be nice as a parent
3:37
Speaker 1: sort of like early heavy metal. All they're doing is shouting. Anyway,
3:40
Speaker 1: one person's music is another person heavy metal screaming. But
3:44
Speaker 1: it's true that the university is filled with incredible and
3:46
Speaker 1: amazing things, and as we look around, we're continually impressed
3:50
Speaker 1: by the complexity of stuff that we see around us.
3:53
Speaker 1: You know, it's not just one kind of sound or
3:54
Speaker 1: one kind of object or one kind of material we
3:57
Speaker 1: find out there in the universe. There's all sorts, and
3:59
Speaker 1: in them is variety and complexity of things that we
4:02
Speaker 1: get to dig into and try to understand. Yeah, because
4:05
Speaker 1: I guess even after millions of years of being humans
4:08
Speaker 1: and looking at the world and listening to the world,
4:10
Speaker 1: there are still things about it that's surprises, Like we
4:12
Speaker 1: are still finding out new kinds of materials and new
4:16
Speaker 1: ways in which matter behaves. That's right, because it turns
4:19
Speaker 1: out that the things around us are not the basic
4:22
Speaker 1: building blocks of the universe. It's not like there's a
4:24
Speaker 1: fundamental ice cream particle and a fundamental tuna sandwich particle
4:28
Speaker 1: that makes up the things you eat or the things
4:30
Speaker 1: that are you. Everything around us is actually made of
4:33
Speaker 1: really small little particles arranged in different ways. And those
4:37
Speaker 1: arrangements can do startling things. You take a set of
4:40
Speaker 1: particles and you can make a kitten. Rearrange those same particles,
4:43
Speaker 1: and you can make lava or neutron star or a
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Speaker 1: blueberry sandwich. It's all the same bits, just arranged in
4:50
Speaker 1: different ways, and we're continuing to discover other ways to
4:53
Speaker 1: arrange those bits to make new, even weirder kinds of stuff. Yeah. Wait,
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Speaker 1: are you telling me that ice cream is not i
5:00
Speaker 1: the mental particle in the universe? It should be. I mean,
5:03
Speaker 1: I know it seems like fundamental to our existence as
5:06
Speaker 1: and it's hard to imagine being human without ice cream.
5:09
Speaker 1: But you know, most humans who have ever lived and
5:12
Speaker 1: never had ice cream, and that is called the human
5:14
Speaker 1: tragedy in literature. Think about it this way. That means
5:17
Speaker 1: there might be some dessert invented by future humans that
5:20
Speaker 1: you never taste. The future humans can't imagine life without.
5:25
Speaker 1: I find it hard to believe that they can improve
5:27
Speaker 1: on ice cream. I take open the fact that in
5:29
Speaker 1: the long run there will partably be more humans that
5:32
Speaker 1: have even ice cream than U have. Not. Well, that's
5:34
Speaker 1: an optimistic view, but I think ice cream is a
5:36
Speaker 1: great example because it's obvious to us that ice cream
5:40
Speaker 1: is not fundamental to the universe, right like ice cream
5:43
Speaker 1: takes special conditions in order to exist, and nobody would
5:46
Speaker 1: be surprised to learn that there might have been a
5:47
Speaker 1: time in the universe when there was no ice cream.
5:49
Speaker 1: It's the same kind of question we ask about other
5:52
Speaker 1: things about whether they're fundamental. Is it necessary to have
5:55
Speaker 1: electrons in the universe? Are they fundamental? Or could there
5:58
Speaker 1: have been a time before or was electrons? Could there
6:01
Speaker 1: be a time in the future without electrons. That's sort
6:04
Speaker 1: of the question about whether something is fundamental or whether
6:07
Speaker 1: it emerges from the complex interplay of fundamental things. So
6:11
Speaker 1: more humans used electrons than not used electrons. Humans are
6:15
Speaker 1: made partially out of electron So I guess we've used
6:17
Speaker 1: them and everything we do right well. I look forward
6:19
Speaker 1: to our future episode about the physics of ice cream.
6:23
Speaker 1: Today on the podcast, we'll be asking a different question
6:25
Speaker 1: about matter and the different ways that it can come
6:28
Speaker 1: together and do interesting and new things. So our question
6:31
Speaker 1: for today is what is topological matter? Topological matter? That's
6:42
Speaker 1: not an everyday word. It's not an everyday word. It's
6:45
Speaker 1: a very recent discovery. Physicists working in their basements, with
6:49
Speaker 1: their lasers and their supercold temperatures and their bizarre materials,
6:52
Speaker 1: have been able to concoct kinds of things no human
6:55
Speaker 1: has ever seen before, to put these same ingredients together
6:58
Speaker 1: in new recipe, to make weird, new kinds of matter
7:02
Speaker 1: that can do things that are familiar matter just cannot do.
7:06
Speaker 1: Man physicists. First, we're talking about physicists as musicians. Now
7:09
Speaker 1: we're talking about them as cook or mad scientists. I
7:12
Speaker 1: wasn't quite sure what you were going for there. I
7:14
Speaker 1: think there's a big overlap between cooks and mad scientists.
7:17
Speaker 1: I think a big part of being a baker is
7:18
Speaker 1: being a mad scientist. You know, Like what happens if
7:20
Speaker 1: I just put a lot of butter in this recipe?
7:23
Speaker 1: Let's see. I don't think that's what I want to
7:26
Speaker 1: hear from when I go to a restaurant. It's like
7:28
Speaker 1: the mad scientist today has a very special treat for you.
7:31
Speaker 1: That's how all of French cooking was invented. Let's just
7:34
Speaker 1: add more butter and see what happens. Oh man, you
7:36
Speaker 1: just call it all a French culture. Man, No, there's
7:40
Speaker 1: an insanity to their creativity which has led to this
7:43
Speaker 1: exquisite discovery of their pastries. They're creative. Yes, yes, that's
7:47
Speaker 1: what we call those kids in class. That kids really creative.
7:51
Speaker 1: I'm looking forward to when the French invent the topological pastry.
7:54
Speaker 1: How do you know they haven't? Can you deform a
7:56
Speaker 1: cross on so that it's equivalent to another pastry? What
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Speaker 1: is the shape of a croissland? Really? And is it
8:01
Speaker 1: a croissant if it's not that shape? Yeah? Well, you know,
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Speaker 1: sometimes we ask if the universe is actually the shape
8:06
Speaker 1: of a doughnut, but maybe we should be asking if
8:08
Speaker 1: it's the shape of a croissant, right, And each quantum
8:11
Speaker 1: field is like a layer in the flakiness of the croissant.
8:13
Speaker 1: That's right. Quantum lamination theory, quantum croissant, quantum heart attack? Really?
8:19
Speaker 1: What is what should call it? For all the ridiculous
8:22
Speaker 1: quantum things out there? I don't know if anybody's ever
8:24
Speaker 1: done quantum pastry yet, I mean much idea. Yeah, but
8:28
Speaker 1: you know, every time I say it on the podcast,
8:29
Speaker 1: we can email from a listener who's like, actually, here's
8:32
Speaker 1: an example. They sell this around the corner. So folks
8:35
Speaker 1: out there, if you've eaten a quantum pastry, send me
8:37
Speaker 1: the recipe. Actually, um, here's a season this this letter.
8:41
Speaker 1: Stop talking about my product. But yeah, topological matter. That's
8:45
Speaker 1: a pretty interesting idea for a name for a kind
8:49
Speaker 1: of material. And I imagine, I mean, the word topological
8:52
Speaker 1: comes up a lot in like mat makers, right, and
8:54
Speaker 1: I guess architects in you know, people who build houses,
8:57
Speaker 1: they have to deal with topological maps a lot, right,
8:59
Speaker 1: exactly In the field of topology is the one that
9:02
Speaker 1: studies questions about shapes and surfaces and asks questions like
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Speaker 1: can you take a donut and smoothly deform it so
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Speaker 1: that it turns into a coffee cup, for example? And
9:13
Speaker 1: the answer is yes, you can. So a topologist says
9:16
Speaker 1: that like, a coffee cup and a doughnut are basically
9:19
Speaker 1: the same shape, and they're both different from like a sphere,
9:22
Speaker 1: because the sphere has no holes in it, and a
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Speaker 1: doughnut and a coffee cup both have one hole in it.
9:27
Speaker 1: So that's the field of topology interesting. And so if
9:30
Speaker 1: you take a donut and dip it into a coffee cup,
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Speaker 1: what does that give you? It gives you a soggy donut.
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Speaker 1: Is that a new kind of shape? But the same
9:39
Speaker 1: as a fear if it sogs, it doesn't it become
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Speaker 1: a sphere. It requires an entirely new field of math.
9:44
Speaker 1: Soggy topology hasn't been invented yet. Deep questions here today
9:48
Speaker 1: and new fields being invented around every corner. But yeah,
9:51
Speaker 1: it's kind of an interesting question. What is topological matter?
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Speaker 1: Maybe it's not something people have heard, or maybe it
9:57
Speaker 1: is something people have heard those usual Daniel went out
9:59
Speaker 1: there to ask people on internet this question. So be
10:02
Speaker 1: grateful to these volunteers who were willing to answer a
10:05
Speaker 1: random question without preparation and have their voice played on
10:08
Speaker 1: the podcast. If you would like to play along for
10:10
Speaker 1: a future episode, please, I totally encourage you. Right to
10:13
Speaker 1: me two questions at Daniel and Jorge dot com. Think
10:17
Speaker 1: about it for a second. How would you answer the
10:19
Speaker 1: question what is topological matter? Here's what people had to say.
10:23
Speaker 1: So I hear the word topological, and I think of
10:25
Speaker 1: a topological map, which sort of gives you an idea
10:28
Speaker 1: for how things are spaced out and organized the elevations.
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Speaker 1: So I'm wondering if topological matter has to do with
10:37
Speaker 1: like the number of protons and neutrons and a nucleus
10:43
Speaker 1: or something. I don't know. I think topology is the
10:47
Speaker 1: study of two day and three day shipes and their properties,
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Speaker 1: and I think there's some rules about how you can
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Speaker 1: compare different shipes topologically. So my guess is the topological
11:00
Speaker 1: comata is matter that conforms to the rules of topology.
11:05
Speaker 1: Topological matter I haven't heard of before, but I imagine
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Speaker 1: it's matter with measurable geometry to it existing in three
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Speaker 1: D space instead of point matter, which might be black hole.
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Speaker 1: I have never heard the term topological matter before, but
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Speaker 1: I think topological is some geometry which has fixed properties.
11:29
Speaker 1: So maybe topological matter is matter whose properties does not change,
11:34
Speaker 1: but I don't know which properties. I'm guessing it's when
11:38
Speaker 1: we're talking about matter and topological I'm guessing it's the
11:41
Speaker 1: shape of sub atomic particles. I have no idea what
11:46
Speaker 1: topological matter is. Is it something that you make maps
11:49
Speaker 1: out of? Topological topography? Is method? Is map making? Right?
11:54
Speaker 1: And I don't know. Topological matter is all of the
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Speaker 1: matter we can see in a three universe? All right?
12:02
Speaker 1: Pretty interesting questions to feel like there's a deep level
12:05
Speaker 1: of knowledge about physics here because I hear a lot
12:08
Speaker 1: of words related to physics. Yeah, people definitely get the
12:12
Speaker 1: clue also that it's related to topology and geometry and
12:16
Speaker 1: thinking about shapes and structures and maps. I like the
12:19
Speaker 1: person who said it's all the matter in the universe technically, yeah,
12:22
Speaker 1: I mean in the universe or there's all kinds of matter.
12:25
Speaker 1: M Yeah, that's true, it's something in the universe. That's
12:28
Speaker 1: a good answer the generic physics question. But do you
12:31
Speaker 1: say something in a universe or the universe or in
12:35
Speaker 1: our universe? All right, So it's kind of an interesting
12:37
Speaker 1: question let's dig into and this conversation is going to
12:40
Speaker 1: get pretty mind blowing and pretty technical and in detailed here.
12:44
Speaker 1: So let's start with the basic question, Daniel, what is
12:47
Speaker 1: topological matter? Yeah, topological matter is something we've only recently
12:52
Speaker 1: invented in the last twenty years or so, and it's
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Speaker 1: something that's different from anything we've ever seen before because
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Speaker 1: it's neither an insulator something that cannot conduct electricity, nor
13:04
Speaker 1: a metal something that can conduct the electricity. So solid
13:07
Speaker 1: state physicists used to divide all kinds of stuff into
13:10
Speaker 1: two categories insulator or metal, and now they've developed this
13:14
Speaker 1: thing which is sort of like neither and both. I see.
13:19
Speaker 1: So solid state physicist is like a physicist that studies
13:22
Speaker 1: I guess solid things, like they don't study energy or
13:25
Speaker 1: particles that they study like materials, yeah, exactly. Sometimes they're
13:29
Speaker 1: called condensed matter physicists, and you know they deal with
13:33
Speaker 1: things like in a lattice, like a crystal, like a
13:35
Speaker 1: big blob of stuff, not plasma, not liquid, but like
13:39
Speaker 1: just a blob of stuff. And the name of the
13:41
Speaker 1: game there's like can you rearrange stuff so it has
13:43
Speaker 1: weird properties? Because you know, I, as a particle physicists,
13:46
Speaker 1: I study like one proton at a time or two
13:49
Speaker 1: of them smashing into each other. But we know that
13:51
Speaker 1: when these protons get together with electrons and make all
13:53
Speaker 1: sorts of interesting structures, crazy things happen. You can get carbon,
13:56
Speaker 1: you can get diamond, you can get all sorts of
13:58
Speaker 1: bizarre stuff. You get ice cream croissance. Yes, yeh. It's
14:01
Speaker 1: sort of studies for like how properties of materials emerge
14:06
Speaker 1: from rearranging the little bits inside matter into new arrangements. Right,
14:10
Speaker 1: And it's like solid stuff. It's not stuff that's like
14:13
Speaker 1: flying around or you know, moving or it's like what
14:16
Speaker 1: can you do with this solid thing? Exactly? And the
14:19
Speaker 1: question of you know, what's a metal what's a conductor
14:22
Speaker 1: is very important because some of this stuff goes into
14:25
Speaker 1: fueling lack our electronics industry. You know, we need insulators
14:29
Speaker 1: and we need conductors to make circuits, and so you
14:32
Speaker 1: can make like new kinds of stuff that has interesting properties.
14:35
Speaker 1: You might be able to make like new weird electronic
14:37
Speaker 1: do hikeys that power the next generation of quantum computers
14:41
Speaker 1: that you're use in your phone as you ride the
14:43
Speaker 1: space elevator up to the moon. Yeah, listening to space
14:46
Speaker 1: elevator music on your quantum phone. And so that you're
14:50
Speaker 1: saying that they see the world as or they see
14:53
Speaker 1: materials usually as either insulators or conductors. That's right. The
14:57
Speaker 1: whole theory of condensed matter physics until about twenty years
15:01
Speaker 1: ago was that materials are either insulators or metals. And
15:04
Speaker 1: they have this whole theory about electrons in bands inside
15:08
Speaker 1: the material that helped them understand that. Okay, so let's
15:11
Speaker 1: get into how do you define conductivity and what makes
15:15
Speaker 1: something not conductive or an insulator. So it's easiest to
15:18
Speaker 1: start out with an individual atom. You remember that atom
15:21
Speaker 1: has a nucleus of right at the core where you've
15:23
Speaker 1: got protons and neutrons, that's where most of the stuff
15:25
Speaker 1: is of the atom, and then around it are the electrons.
15:28
Speaker 1: And electrons around an atom have these energy levels, right
15:31
Speaker 1: because they're quantum particles. But now we want to think
15:33
Speaker 1: about a whole bunch of atoms, right, you want to
15:35
Speaker 1: put them together, stack them together like legos to make
15:38
Speaker 1: a blob of stuff, because that's what condensed matter solid
15:41
Speaker 1: state physics is about. It is about like a crystal
15:44
Speaker 1: lattice of stuff. So material is sort of like a
15:46
Speaker 1: grid of atoms. And now we want to think about
15:49
Speaker 1: like how electrons can move through that grid of atoms.
15:52
Speaker 1: And you know, an individual atom has its electrons and
15:54
Speaker 1: the next one has its electrons, and the material is
15:57
Speaker 1: a conductor when an electron can hop from one atom
16:00
Speaker 1: to the next, when you can sort of like jump
16:02
Speaker 1: around slide around easily. And material is an insulator when
16:05
Speaker 1: you can't, when it's sort of like stuck on one
16:07
Speaker 1: atom no matter how hard you push it. Well, I
16:09
Speaker 1: think this is something that maybe a lot of people
16:11
Speaker 1: don't think about when you know, I think when you
16:13
Speaker 1: grow up and you learn about like a wire conducting electicity,
16:16
Speaker 1: you think of like one electron going into the wire
16:18
Speaker 1: and then traveling through the wire and then coming out
16:20
Speaker 1: the other end. But really that's not what's happening in
16:23
Speaker 1: conducting metals. It's it's more like electrons are being passed,
16:27
Speaker 1: traded around from one end to the other, right, that's right.
16:30
Speaker 1: You should sort of think of it like a hose,
16:32
Speaker 1: but instead of an empty hose that you're passing one
16:34
Speaker 1: electron all the way through, think about like a hose
16:37
Speaker 1: it's already filled with electrons. You're pushing one in and
16:41
Speaker 1: then another electron pops out the other side. So all
16:44
Speaker 1: the electrons slide down the whole like one notch, and
16:47
Speaker 1: one electron pops out the other side, but not the
16:49
Speaker 1: one that you put in originally, you know, on your
16:51
Speaker 1: side or maybe right, like, we don't know. It's like
16:54
Speaker 1: it's it's a bit of a mess. It's like you
16:55
Speaker 1: put an electron on one end and maybe that one
16:58
Speaker 1: will hop to the next one, or maybe it'll stay in,
17:00
Speaker 1: but it will kick off an electron from the existing atom,
17:03
Speaker 1: and that one will go to the next atom, and
17:04
Speaker 1: who knows what's going to happen, right, Yeah, Well, the
17:06
Speaker 1: more orderly it is, the more it happens, Like you know,
17:09
Speaker 1: everybody's sliding down one chair in the bus or something.
17:12
Speaker 1: Then the better the conductivity, the more messy it is,
17:14
Speaker 1: the more electrons bounce around and go in the wrong direction,
17:17
Speaker 1: the worst the conductivity is. That's why we have some
17:19
Speaker 1: conductors that are excellent in the conductors that are sort
17:21
Speaker 1: of poor conductors. Right, And so what makes something more
17:24
Speaker 1: conductive or one atom more prone to conductivity than others.
17:28
Speaker 1: Is it just that it's electrons aren't like held on tightly,
17:31
Speaker 1: or that there are at the surface and you know,
17:33
Speaker 1: the atom can sort of take them relieve them. The
17:35
Speaker 1: key thing is what energy levels are available to the electron.
17:39
Speaker 1: So for an atom, you just have like a ladder
17:41
Speaker 1: of energy levels and the electron can go up or
17:43
Speaker 1: down those energy levels. But when you put all these
17:45
Speaker 1: atoms together to make a material, something different happens. Instead
17:49
Speaker 1: of having just like a full ladder of energy levels,
17:52
Speaker 1: you get these bands that the electron can be into.
17:54
Speaker 1: You have like a bunch of energy levels clustered together,
17:57
Speaker 1: and then a gap where like electrons are not allowed
17:59
Speaker 1: to have those energies, and then maybe there's another band
18:02
Speaker 1: above it. And so this makes something an insulator. If
18:05
Speaker 1: for example, a band is all full if a band
18:08
Speaker 1: is all filled with electrons, is like no room for
18:11
Speaker 1: electrons to jump in there unless they have crazy high energy.
18:15
Speaker 1: So an insulator is one where you would need to
18:17
Speaker 1: give the electron enormous energy so it could jump up
18:20
Speaker 1: into the next band to move around. But normally electrons
18:23
Speaker 1: don't have that energy, so they're sort of stuck where
18:26
Speaker 1: they are. I feel like we're talking about heavy metals
18:28
Speaker 1: and bands here. Hand. It's confusing my brain a little bit.
18:32
Speaker 1: I think what you mean is, you know, electrons are
18:35
Speaker 1: happy in certain energy levels around an atom, but when
18:38
Speaker 1: you put a lot of atoms together, you know, things
18:40
Speaker 1: get kind of fuzzy now, and an electron can be
18:43
Speaker 1: happy sort of a multiple levels because it's near another atom, right,
18:47
Speaker 1: But sometimes it can work out that there are big
18:49
Speaker 1: gaps in like these energy levels. That's what you mean
18:51
Speaker 1: by a band, right, It's like a sort of like
18:53
Speaker 1: a gap in the sort of the different levels that's right,
18:56
Speaker 1: the band are the allowed energy levels, and then there's
18:58
Speaker 1: gaps between these bands, and an insulator has a really
19:01
Speaker 1: big gap between the bands, and the lower band is
19:04
Speaker 1: like all filled up, so that if an electron is
19:06
Speaker 1: in that lower band, it can't just like jump to
19:09
Speaker 1: the next atom, because the next atom is also filled up,
19:12
Speaker 1: there's like no empty chairs and a conductor and a metal.
19:16
Speaker 1: Then the band is only half filled, and so the
19:18
Speaker 1: neighboring atoms have empty chairs for an electron to jump into.
19:21
Speaker 1: They can slide over to the next one, sort of
19:23
Speaker 1: like if you have a bottle and it's half filled
19:26
Speaker 1: with water, it's a lot easier to slash the water
19:29
Speaker 1: around than if you have a bottle it's totally filled
19:31
Speaker 1: with water, because it's sort of like packed in there.
19:33
Speaker 1: Nothing can move. And so if you have your band
19:35
Speaker 1: half filled, then the electrons can slide around from atom
19:38
Speaker 1: to atom. If your band is totally filled, that's an insulator.
19:41
Speaker 1: Then the electrons are sort of all stuck and nobody
19:43
Speaker 1: can go anywhere. Right, But I guess you make it
19:45
Speaker 1: sound like it's just a matter of having too many
19:47
Speaker 1: or too little electrons. It's really, But but really it's
19:50
Speaker 1: more of a question of like the structure of the crystal,
19:52
Speaker 1: right exactly. These bands come from the structure of the crystal.
19:56
Speaker 1: Like you might wonder, why are there bands in a
19:58
Speaker 1: crystal when there aren't band for an atom, There aren't
20:01
Speaker 1: like these gaps where electrons are not allowed to have
20:03
Speaker 1: the energy level in an atom, where do they come
20:05
Speaker 1: from in a crystal? And that's the really interesting thing, right,
20:08
Speaker 1: is that when you put atoms together into a crystal,
20:10
Speaker 1: they get properties that the individual atoms don't have. And
20:13
Speaker 1: what's going on is the spacing between the atoms. As
20:17
Speaker 1: an electron passes through the crystal, sometimes it reflects off
20:22
Speaker 1: of those atoms and bounces back and defracts and destructively
20:25
Speaker 1: interferes with itself. And so if the energy of the
20:28
Speaker 1: electron is such that the wavelength of its wave function
20:32
Speaker 1: is similar to the spacing of the atoms in this crystal,
20:35
Speaker 1: then you get all sorts of complex destructive interference and
20:37
Speaker 1: electrons basically just can't have those energy levels. Mmm. Interesting.
20:42
Speaker 1: It has to do with the waveform of the electrons
20:44
Speaker 1: and how close or how far apart the crystal puts
20:47
Speaker 1: the atoms together exactly. And the really fascinating thing is
20:50
Speaker 1: that you could take the same material, the same elements,
20:53
Speaker 1: and arrange them in different crystal structures and you get
20:56
Speaker 1: different bands. So, for example, if you take tin, tin
20:59
Speaker 1: has two different crystal structures, they call it gray tin
21:02
Speaker 1: and white tin based on how it looks to your eye,
21:05
Speaker 1: and white tin is a conductor, whereas gray tin is
21:08
Speaker 1: an insulator. It's exactly the same stuff, but you can
21:11
Speaker 1: build it together in different ways, sort of like using
21:13
Speaker 1: the same legos to make something slightly different. The crystal
21:16
Speaker 1: relationships are different, so the spacing is different, and so
21:19
Speaker 1: electrons behave differently in those materials because I guess, you know,
21:23
Speaker 1: the properties or the levels of one atom sort of
21:26
Speaker 1: start to interfere with the properties and levels of its neighbors,
21:30
Speaker 1: and so things sudden will become like prohibitive or easy
21:33
Speaker 1: to kind of move around, exactly, And the properties of
21:36
Speaker 1: a whole set of things can be very different from
21:38
Speaker 1: the properties of one. Like you ever go listen to,
21:41
Speaker 1: you know, children's choirs, like, well, one kid on their
21:44
Speaker 1: own kind of terrible. But if you get like thirty
21:46
Speaker 1: kids singing a song together, like it sort of averages
21:48
Speaker 1: out to give you, like something maybe pleasant to listen to,
21:55
Speaker 1: spoken like a true parent exactly. And so I think
21:58
Speaker 1: this is really fascinating, And for a long time people thought,
22:01
Speaker 1: well that was it. That it's all about having these
22:03
Speaker 1: bands and it's determined by the crystal structure. That the
22:06
Speaker 1: crystal structure tells you whether something is insulator or something
22:10
Speaker 1: as a conductor. And this is called the band theory,
22:12
Speaker 1: and it's sort of rained in condensed matter physics for
22:15
Speaker 1: decades and decades, and people thought this is how conduction
22:19
Speaker 1: works in materials. It's all about the structure of the crystal,
22:23
Speaker 1: like the arrangement of the atoms that will determine what's
22:26
Speaker 1: an insulator or a conductor exactly, and like not the
22:29
Speaker 1: shape of the material. Doesn't matter how big a blob
22:31
Speaker 1: you have, or how thin it is or how thick
22:33
Speaker 1: it is. It's just about the nature of the material
22:35
Speaker 1: and its crystal structure. This rain supreme. People thought of
22:38
Speaker 1: this for a long time. But I'm guessing that there's
22:41
Speaker 1: a twist to this story where everything is proven wrong.
22:44
Speaker 1: That's usually how it works in physics, isn't it. That's right.
22:47
Speaker 1: Here comes the revolution, and so let's get into the
22:49
Speaker 1: plot twist here. But first let's take a quick break.
23:04
Speaker 1: All right. We're talking about topological matter, and we were
23:08
Speaker 1: talking about how something We used to think that everything
23:11
Speaker 1: was either a conductor or an insulator, meaning it can
23:15
Speaker 1: conduct electricity or not conduct electricity, and that we thought
23:19
Speaker 1: it had everything to do with the way that the
23:21
Speaker 1: structure of the material, in the way in which the
23:23
Speaker 1: atoms suld have compacted together and form crystals. But now
23:27
Speaker 1: there's a plot to with Daniel, So we learned some
23:29
Speaker 1: new information. That's right. Clever people thinking hard about the
23:32
Speaker 1: way these things work came up with an idea for
23:34
Speaker 1: how to build a new kind of material. And this
23:37
Speaker 1: is super cool because it came out of people's brains.
23:40
Speaker 1: This is not something we like discovered in the lab
23:43
Speaker 1: and we're like, look at this weird kind of stuff
23:44
Speaker 1: we built. Oh my gosh, you can do something weird.
23:47
Speaker 1: This came out of smart people scratching their heads and
23:49
Speaker 1: drinking coffee and scribbling in their notebooks and doing calculations,
23:53
Speaker 1: and they were able to come up with an idea
23:54
Speaker 1: for how to build something which is called the topological material,
23:58
Speaker 1: which is an insulator on the inside but a conductor
24:02
Speaker 1: on the surface. So like the outer edges of a lava,
24:06
Speaker 1: this stuff will conduct electricity, but the interior of it
24:09
Speaker 1: will not. Interesting so sort of like a coating almost
24:13
Speaker 1: like you have something that doesn't conduct electricity, like like
24:16
Speaker 1: a ceramic or something, and then you codd with something
24:18
Speaker 1: that does conduct electricity. No it's all one material. So
24:22
Speaker 1: you have like some kind of material and inside it
24:26
Speaker 1: doesn't conduct electricity, but then the same material on the surface,
24:29
Speaker 1: the surface of that same material. It's all uniform and
24:32
Speaker 1: homogeneous what the stuff is, but the surface of it
24:35
Speaker 1: does conduct electricity. Oh wait, it's the same material with
24:39
Speaker 1: the same structure, or is it on the surface you
24:42
Speaker 1: have a different structure. It's the same material with the
24:45
Speaker 1: same structure. But now the behavior of the material depends
24:48
Speaker 1: on where you are in the shape. If you're on
24:50
Speaker 1: the edge, you conduct electricity. If you're in the middle,
24:53
Speaker 1: in the bulk, you insulate. WHOA, So how does that work?
24:57
Speaker 1: Like how can something conduct only on the surface. Yeah,
25:00
Speaker 1: it's really interesting. It has to do with how electrons move.
25:03
Speaker 1: And so we talked previously about insulators being when electrons
25:06
Speaker 1: are stuck. So now imagine a material where electrons aren't
25:09
Speaker 1: quite stuck and they're not like exactly stuck on one atom.
25:12
Speaker 1: They can sort of like move in little circles. And
25:14
Speaker 1: that doesn't allow this to conduct electricity because electrons like
25:18
Speaker 1: sort of can't move all together. Like you move in
25:20
Speaker 1: a circle, you end up back where you started. So
25:22
Speaker 1: there's no effective flow of electricity. But if electrons are
25:26
Speaker 1: moving in a circle, then think about what happens on
25:29
Speaker 1: the surface or near the surface. Instead of having electrons
25:32
Speaker 1: moving little loops, their loops are sort of like cut
25:34
Speaker 1: in half, and so now they can only do sort
25:37
Speaker 1: of like half of the loop before they hit the surface,
25:39
Speaker 1: and then they can do the next loop, and the
25:41
Speaker 1: next loop in the next loop, and that sort of
25:43
Speaker 1: like adds up to the electrons can now flow all
25:46
Speaker 1: the way around the edge of the material because they're
25:49
Speaker 1: only doing half of these loops. Wait what, well, I
25:52
Speaker 1: guess first of all, I back up a little bit.
25:55
Speaker 1: What do you mean electrons moving little loops, like little
25:57
Speaker 1: loops around the atom, or little loops like around multiple atoms,
26:01
Speaker 1: or what do you mean? Because they're already sort of
26:03
Speaker 1: in loops in orbit around the nucleus of each atom.
26:05
Speaker 1: But so what do you mean by they move in loops?
26:08
Speaker 1: The first idea for how to build these things was
26:09
Speaker 1: to have them move in little orbits around several atoms.
26:13
Speaker 1: And they created this first by having really powerful magnetic fields,
26:16
Speaker 1: which will make electrons move in little circles. Why do
26:19
Speaker 1: they think to make the electrons move in circles? Because
26:22
Speaker 1: they were hoping to get exactly this effect. They were
26:24
Speaker 1: hoping to do something which on the center of the
26:27
Speaker 1: materials would make us to the electrons effectively we can't
26:29
Speaker 1: go anywhere because they're stuck in this little circle, but
26:32
Speaker 1: that on the edges would have a different behavior that
26:35
Speaker 1: you know, these circles are sort of cut in half
26:37
Speaker 1: on the edges, and so they only go in one direction.
26:40
Speaker 1: Like in the center of the material, the electrons basically
26:42
Speaker 1: go back and forth because they're moving in a circle,
26:45
Speaker 1: but near the edges they can only do the back right,
26:48
Speaker 1: So all those electrons are now moving in the same direction,
26:50
Speaker 1: and that's effectively conducting electricity. It's like having a flow
26:54
Speaker 1: of the electrons all the way around the edge. Okay,
26:57
Speaker 1: so you need an electromagnetic field to make these things
27:00
Speaker 1: going little loops or were you saying that these things
27:02
Speaker 1: go in loops. Anyways, So the original design for these things,
27:05
Speaker 1: and the first way they were realized in the lab
27:07
Speaker 1: was to make a really strong magnetic feel to make
27:09
Speaker 1: electrons do this. Later on people realized, oh, there are
27:12
Speaker 1: other ways to do this, you know, just to get
27:14
Speaker 1: the electrons to like do loops around their atoms into
27:17
Speaker 1: couple like their orbits and their spins. But that's a
27:19
Speaker 1: bit more technical. So the first way people made this
27:21
Speaker 1: happen was to have the electrons do these little dances
27:24
Speaker 1: in a circle. It's sort of like a big square dance, right.
27:26
Speaker 1: Imagine everybody's like dancing and they've hooked their arms together.
27:29
Speaker 1: You're not really going anywhere, but if you're on the edge,
27:32
Speaker 1: then you're sort of getting passed from partner to partner
27:34
Speaker 1: and you're gonna end up moving all the way around
27:36
Speaker 1: the square dance. So what you're saying that normally the
27:39
Speaker 1: electrons don't conduct, but they move in circles around inside
27:44
Speaker 1: of the material. So it's a conductor on the inside,
27:47
Speaker 1: or no, it's an insulator on the inside because the
27:49
Speaker 1: electrons are trapped. They can't really go anywhere, they're stuck
27:51
Speaker 1: moving in these circles. But it's a conductor on the
27:54
Speaker 1: surface because these circles are cut in half, and so
27:57
Speaker 1: the effective path of the electron is all to point
27:59
Speaker 1: in the same direction. Oh, I see, Okay. I think
28:02
Speaker 1: asking us to sort of think about these loops and
28:04
Speaker 1: these structures is kind of hard on an audio podcast,
28:07
Speaker 1: But I think what I'm getting is that inside of
28:08
Speaker 1: the material. The conditions of the crystal are such the
28:12
Speaker 1: electrons that are sort of stuck moving around in circles,
28:15
Speaker 1: but at the edges, because there's no full circle they
28:18
Speaker 1: can do. Then they can then jump around and move
28:21
Speaker 1: to other atoms. Is that what you're saying. Yeah, they
28:23
Speaker 1: can jump from atom to atom on the surface exactly
28:26
Speaker 1: because you're sort of breaking the conditions that are making
28:29
Speaker 1: them be stuck in these loops. Yeah, they only do
28:32
Speaker 1: half of the loops, right, and the half of the
28:34
Speaker 1: loops basically always point in the same direction. So you
28:36
Speaker 1: do half of one loop, and you do half the
28:38
Speaker 1: next loop, and the half the next loop. You never
28:39
Speaker 1: do the other half of any of these loops because
28:42
Speaker 1: the surfaces they're sort of preventing you. Let me just
28:44
Speaker 1: try one more visual analogy. So think about like a
28:48
Speaker 1: swimming pool in your backyard. Now, put a lot of
28:51
Speaker 1: tiny whirlpools in it, all swirling around. Fill the whole
28:55
Speaker 1: thing up with whirlpools. Now, what happens if you toss
28:58
Speaker 1: a ping pong ball into it, Well, it's going to
29:00
Speaker 1: get stuck in one of the whirlpools, and it will
29:03
Speaker 1: be really hard for it to jump from one to
29:05
Speaker 1: the other. So that's like an electron getting stuck moving
29:08
Speaker 1: in a circle around one of the atoms in a crystal.
29:11
Speaker 1: But if you put it right at the edge of
29:13
Speaker 1: the pool where the whirlpools are all pushing in the
29:16
Speaker 1: same direction, so that instead of getting stuck in one whirlpool,
29:20
Speaker 1: it moves around the whole edge of the pool, getting
29:23
Speaker 1: passed from one whirlpool to another. So it doesn't conduct
29:26
Speaker 1: the electricity in the center, but it does around the edges.
29:30
Speaker 1: So that gives you a material if you can make it,
29:32
Speaker 1: that doesn't conduct electrons through the material, but it conducts
29:36
Speaker 1: electrons on the surface of it. That's right exactly. And
29:39
Speaker 1: this sort of blew everybody's minds because they were like,
29:41
Speaker 1: what is it. Is it an insulator, is it a conductor?
29:44
Speaker 1: Is it both? Is it neither? It's something new, and
29:47
Speaker 1: so this sort of blew up this whole band theory
29:50
Speaker 1: of materials and made people realize that there's like a
29:53
Speaker 1: whole possibility for new things that you could build that
29:56
Speaker 1: have weird behaviors that you didn't possibly anticipate. And the
30:00
Speaker 1: cool thing is that this idea came about and just
30:02
Speaker 1: like a couple of years later, people were able to
30:04
Speaker 1: make them, so went from like crazy idea in somebody's
30:07
Speaker 1: notebook to like, Okay, we made it, We saw it
30:09
Speaker 1: actually do this thing in just a couple of years,
30:12
Speaker 1: which is sort of astounding. I guess maybe the confusing
30:14
Speaker 1: thing might be that the way you describe it doesn't
30:16
Speaker 1: sound so different, Like what I could just maybe take
30:19
Speaker 1: a ceramic and coated with the conducting metal and I
30:21
Speaker 1: would get something that's conductive on the outside and not
30:24
Speaker 1: on the inside. Like why can you explain maybe why
30:27
Speaker 1: this was so revolutionary. Well, it's different from having a
30:30
Speaker 1: ceramic coated with a metal, right, that's just having a
30:33
Speaker 1: metal that conducts. Here we have something which is fundamentally
30:35
Speaker 1: different because it's the same material all the way through,
30:38
Speaker 1: but that material behaves differently on the inside and the outside.
30:42
Speaker 1: And that's exciting because it suggests that you can get
30:45
Speaker 1: new properties for familiar materials, the materials you thought you knew.
30:49
Speaker 1: You might get them to do different kinds of things,
30:52
Speaker 1: different weird kinds of things if you create new conditions
30:55
Speaker 1: for them that there's like a whole other avenue. It's
30:57
Speaker 1: sort of like you've been playing with your legos for
30:59
Speaker 1: ten years and your friend comes over and build something
31:02
Speaker 1: mind blowing, You're like, what I never thought legos could
31:05
Speaker 1: do that. That's awesome, and it gives you ideas for
31:07
Speaker 1: all sorts of other things you might be able to
31:09
Speaker 1: build with your legos you never even considered. And in
31:11
Speaker 1: this case it's exciting because the outside surface of these
31:14
Speaker 1: topological conductors are very very low resistance. For example, they
31:19
Speaker 1: can conduct electricity better than copper, better than gold. They're
31:23
Speaker 1: not quite super conductors with zero resistance, but they're better
31:27
Speaker 1: conductors than almost any material we have and the operator
31:31
Speaker 1: room temperature. So it's promising that there might be like
31:33
Speaker 1: new kinds of things we can build. And that's kind
31:35
Speaker 1: of what's called topological matter because it's sort of happens
31:38
Speaker 1: on the surface, like the fun things happened on the surface.
31:43
Speaker 1: It's tempting to think about that because it sounds like
31:46
Speaker 1: we're saying, well, the properties of these material doesn't just
31:49
Speaker 1: depend on the crystal structure, you know, on like the
31:52
Speaker 1: organization internally, but also in the shape of the object,
31:55
Speaker 1: because originally these things were made super flat, and we're
31:58
Speaker 1: talking about like the shape and the nucture of it. Actually,
32:01
Speaker 1: in this case, topological refers to something much more technical.
32:04
Speaker 1: Physicists like to think about these things in terms not
32:07
Speaker 1: in physical space, but in something else called momentum space,
32:10
Speaker 1: where you do like a fury transform from physical space
32:12
Speaker 1: to momentum space, and then in that momentum space they're
32:15
Speaker 1: doing some complex analysis, some complicated counting of the shape
32:19
Speaker 1: of that space, and it turns out there are really
32:21
Speaker 1: interesting symmetries. They're like states there that have the same
32:24
Speaker 1: topology will tend to have the same kind of behavior,
32:27
Speaker 1: will be an insulator, or will be a conductor. But
32:29
Speaker 1: I think that's a little bit deeper on the mathematics
32:31
Speaker 1: than we want to get into today. Well, I guess
32:33
Speaker 1: maybe step us through. Then. What are some of the
32:35
Speaker 1: ways in which it blew people's mind, Like, what were
32:37
Speaker 1: some of the cool things that people found you can
32:39
Speaker 1: do with these Well, we're just really beginning and exploring
32:42
Speaker 1: what you can do them, and we're talking a minute
32:43
Speaker 1: about potential applications. But one of the really interesting things
32:46
Speaker 1: is that people went back to old experiments that they
32:49
Speaker 1: never really understood before. Like people have been, you know,
32:52
Speaker 1: doing weird things with gold for a long time, and
32:55
Speaker 1: sometimes they would do experiments and not really understand the
32:58
Speaker 1: results and see they were sort of scratch their head
33:00
Speaker 1: and then move on. And now with this new understanding,
33:03
Speaker 1: we can look back and realize, oh, we were seeing
33:06
Speaker 1: topological effects in ordinary materials. We just didn't really understand it.
33:10
Speaker 1: Like people took gold and they made like thinner and
33:13
Speaker 1: thinner sheets of gold, and they studied the conductivity of it,
33:16
Speaker 1: and they were sort of surprised that it didn't really
33:18
Speaker 1: depend on like the thickness of the gold and only
33:21
Speaker 1: depended on the surface area of the gold. And that
33:24
Speaker 1: was weird because people thought, like, you should depend on,
33:26
Speaker 1: you know, the crystal structure and what's going on inside.
33:29
Speaker 1: And so there's like a whole list of experiments that
33:32
Speaker 1: people didn't really understand, sort of befuddled the field. And
33:34
Speaker 1: now people go back and like, oh, wow, it turns
33:36
Speaker 1: out that's a topological material. And more broadly, as we
33:40
Speaker 1: look at it now, people are realizing that something like
33:43
Speaker 1: one third of all materials that are out there have
33:46
Speaker 1: some sort of these topological effects that it turns out
33:49
Speaker 1: to have been everywhere all the time, we just never
33:51
Speaker 1: noticed it, and the other two thirds just don't have
33:53
Speaker 1: these effects. And so now we're doing these like really
33:56
Speaker 1: complicated calculations to try to understand, like under what condition
34:00
Speaker 1: can you get these kinds of effects. And it turns
34:02
Speaker 1: out that, you know, a lot of things that we
34:04
Speaker 1: think of as insulators turn out to have some amount
34:07
Speaker 1: of topological conductivity, and things that we think about as
34:11
Speaker 1: conductors sometimes are insulators on the inside. And so it's
34:15
Speaker 1: like being unaware of a third phase of matter. You know.
34:17
Speaker 1: It's like if you're a fish scientist, you've been swimming
34:20
Speaker 1: around water forever and then you go to the surface
34:22
Speaker 1: and you discover, oh wow, there's other things. You know,
34:25
Speaker 1: water has other phases. I never even realized. You know,
34:28
Speaker 1: it's like opening up an entirely new area for people
34:31
Speaker 1: to explore. It's it's really the beginning of a revolution
34:34
Speaker 1: in condensed matter physics. It's like maybe like figuring out
34:37
Speaker 1: that water can form little layers and on solid things,
34:40
Speaker 1: and then little animals can live on that surface. Stuff
34:43
Speaker 1: like that, Or like a fish discovering rain, You're like,
34:46
Speaker 1: oh wow, water falls through the sky and these weird
34:48
Speaker 1: little drops. How interesting. I need to invent an umbrella exactly.
34:53
Speaker 1: And the other interesting thing is that this is a
34:55
Speaker 1: discovery that was just sort of like sitting there waiting
34:58
Speaker 1: to happen, like mathe medical tools that were used to
35:01
Speaker 1: come up with this idea, and then mid two thousand's
35:04
Speaker 1: are ancient. This could have been thought of in the fifties,
35:07
Speaker 1: and the experimental results were sitting out there in the
35:09
Speaker 1: literature for decades. You know, it's like this pattern of
35:12
Speaker 1: unexplained experimental measurements that nobody was able to put together.
35:15
Speaker 1: So when they put this story together, it's sort of like,
35:17
Speaker 1: oh my god, it's so fascinating but kind of obvious.
35:21
Speaker 1: And that's really exciting to me as a physicist because
35:23
Speaker 1: it tells me like, well, what other discoveries are just
35:26
Speaker 1: out there waiting, Like there's gonna be a whole series
35:28
Speaker 1: of Nobel Prizes, one for the topological materials, and all
35:32
Speaker 1: of that information was just like literally sitting out there
35:35
Speaker 1: waiting for almost anybody to put it together. Now, is
35:37
Speaker 1: a Nobel Prize medal going to be topological material as well? Well?
35:42
Speaker 1: One cool effect I think you wrote down here is
35:44
Speaker 1: that you can take an insulator and turn it into
35:47
Speaker 1: a conductor and back again just by changing its shape. Yeah,
35:51
Speaker 1: people used to think that if you had a material
35:53
Speaker 1: that's an insulator and you sort of started pulling it apart,
35:56
Speaker 1: you made the atoms further and further apart, then it
35:59
Speaker 1: would stay in insulatly because as the atoms get further
36:01
Speaker 1: and further apart, obviously it gets harder and harder for
36:04
Speaker 1: electrons to jump from one to the other. And so
36:06
Speaker 1: this is sort of like a common belief that all
36:08
Speaker 1: insulators are insulators even if you pull them apart. Well,
36:10
Speaker 1: if you have a topological material, then what happens when
36:13
Speaker 1: you start pulling it apart is that that insulator at
36:16
Speaker 1: the core becomes a conductor because you're effectively now creating
36:21
Speaker 1: like new surfaces, and these things can conduct at surfaces.
36:25
Speaker 1: And then as you keep pulling it apart, then you know,
36:27
Speaker 1: the atoms get so far apart that they're basically not
36:30
Speaker 1: part of a material anymore, and it's effectively an insulator.
36:33
Speaker 1: So it's a really weird kind of material that you know,
36:36
Speaker 1: the conductivity of it also depends on how you smoothly
36:40
Speaker 1: deform it. Interesting, so it didn't conduct before even at
36:43
Speaker 1: the surface, but once you pull it apart, you're sort
36:45
Speaker 1: of rearranging the atoms in such a way that suddenly
36:48
Speaker 1: on the surface it can conduct. Yeah, exactly. It's really interesting,
36:51
Speaker 1: and so this gets condensed. Matter of physic is very
36:53
Speaker 1: excited about the kinds of things they might be able
36:56
Speaker 1: to invent using these techniques or other techniques similar in
36:59
Speaker 1: the future. Are they thinking topological ice cream? That's right.
37:04
Speaker 1: It's frozen in the middle and liquid on the center.
37:07
Speaker 1: Mean that discovery has been there all these years for
37:10
Speaker 1: people to find. That's right. You get the ice cream
37:12
Speaker 1: Nobel Prize. The Nobel Prize made out of ice cream.
37:14
Speaker 1: You just have to keep it in the freezer otherwise
37:16
Speaker 1: it melts. All right, Well, let's get into what this
37:18
Speaker 1: new kind of material can do. What are some of
37:21
Speaker 1: the exciting things that might be able to be made
37:24
Speaker 1: from these and what the potential of that is. But first,
37:26
Speaker 1: let's take another quick break. All right, we're talking about
37:42
Speaker 1: ice cream Nobel Prizes for discovering new flavors or or
37:47
Speaker 1: discovering ice cream that doesn't melt. That's right. Well, you
37:50
Speaker 1: know I would take two blobs of ice cream and
37:52
Speaker 1: accihilarate them at high speed and moush them together and
37:54
Speaker 1: see if a new flavor comes out. Well, nobody would
37:57
Speaker 1: give you a Nobel Prize, But if you can find
38:00
Speaker 1: a solid state ice cream that's permanently solid. And maybe
38:03
Speaker 1: you got something there room temperature ice cream. Now there
38:05
Speaker 1: would be an invention. Well, it's at you can eat
38:08
Speaker 1: in the winter, maybe, So it's a new kind of material,
38:11
Speaker 1: these topological matter materials because they have interesting conducting and
38:15
Speaker 1: non conducting property. So what are some of the things
38:18
Speaker 1: you can do with them? Well, one of the most
38:19
Speaker 1: useful immediate applications are to use them to build computer chips.
38:24
Speaker 1: The basis of all modern computing and your phone and
38:27
Speaker 1: your laptop and your iPad and everything use these these
38:30
Speaker 1: little silicon chips that have tiny little circuits, and those
38:34
Speaker 1: circuits are mostly transistors put together in different ways to
38:37
Speaker 1: make logic gates. And those are printed using silicon, which
38:40
Speaker 1: is a fascinating material because you can dope it in
38:42
Speaker 1: one way to make it a conductor, and dope it
38:44
Speaker 1: another way to make it an insulator. So you can
38:46
Speaker 1: print these circuits. One issue is that these things get
38:49
Speaker 1: hot right as electrons pass through the silicon when it's
38:52
Speaker 1: in its conducting mode, it's not perfectly conducting, and so
38:55
Speaker 1: it heats up a little bit. And if you know,
38:57
Speaker 1: for example, your laptop, right it gets hot when you're
38:59
Speaker 1: running really complex game on it, and that wastes a
39:03
Speaker 1: lot of heat, right, Yeah, I guess that's an effect
39:05
Speaker 1: that I thought I knew how to work, but now
39:07
Speaker 1: I don't because of this conversation. Because I always felt like, Okay,
39:10
Speaker 1: it's electrons going through the copper, and so it's somehow
39:13
Speaker 1: creating some kind of friction and that's where the heat
39:16
Speaker 1: comes from. But how does resistance cause heat? Well, resistance
39:20
Speaker 1: is when you're taking the motion of the electrons and
39:22
Speaker 1: you're just converting it to the heat of the material,
39:24
Speaker 1: meaning that like you know, an atom absorbs that electron,
39:27
Speaker 1: and now that atom is just sort of like has
39:29
Speaker 1: more energy, so you like sped up the motion of
39:32
Speaker 1: that atom, and so instead of the electrons just like
39:35
Speaker 1: sort of surfing along on top of the atoms, some
39:38
Speaker 1: of that energy is sort of like sucked down into
39:40
Speaker 1: the atom and trapped to energize the lattice, to shake
39:43
Speaker 1: up those atoms in the lattice, And that's what you
39:45
Speaker 1: don't want. You want to keep it cold, you want
39:48
Speaker 1: to keep it firm. It doesn't conduct as well when
39:50
Speaker 1: it gets warm also, so it gets worse and worse.
39:53
Speaker 1: And so what you like is something which stays cold,
39:56
Speaker 1: it just passes the electricity through it. And not just
39:59
Speaker 1: because they would be form better and faster, but also
40:01
Speaker 1: because it's a huge waste of energy. You know, something
40:04
Speaker 1: like ten percent of our worldwide energy use goes to
40:08
Speaker 1: running computers. And if we can make that more efficient
40:12
Speaker 1: and we can find materials that have less resistance, then
40:15
Speaker 1: these computers can operate more efficiently and they can operate
40:17
Speaker 1: faster and more reliably. Yeah, if you can take a
40:20
Speaker 1: chunk out of that, you know, ten percent of worldwide
40:23
Speaker 1: energy that you would save a lot. And so these
40:26
Speaker 1: materials are better conductors than for example, copper is and
40:30
Speaker 1: so that's very promising. Practically speaking, there are big obstacles there, right.
40:34
Speaker 1: You can't just be like, oh, I have a new
40:35
Speaker 1: complex kind of material which only works in the lab
40:38
Speaker 1: in tiny microduces. Can we now insert it into everyday electronics?
40:43
Speaker 1: You know, if you want to get into the supply
40:45
Speaker 1: chain for the Apple iPhone, then there's a lot of
40:48
Speaker 1: constraints there. You have to be like cheap and available,
40:51
Speaker 1: you have to be ductiles so you can make wires
40:53
Speaker 1: out of it. So there's a long road to go there,
40:56
Speaker 1: but it's it's sort of promising maybe give us a
40:58
Speaker 1: sense of how difficult to is to make these materials,
41:01
Speaker 1: Like what's the standard way to make a topological matter conductor,
41:05
Speaker 1: like using what kind of materials? Yeah, so originally you
41:08
Speaker 1: have to make them really really thin and have very
41:10
Speaker 1: powerful magnetic fields. These days, people have made three D
41:14
Speaker 1: topological materials, and the way they do it is sort
41:18
Speaker 1: of similar to the way you operate with semiconductors, which
41:21
Speaker 1: is that you add other kinds of things, so you
41:23
Speaker 1: like inject weird things into the crystal lattice to get
41:26
Speaker 1: these effects on the surface you mean on the surface
41:29
Speaker 1: or in the center also, but you end up getting
41:31
Speaker 1: the same effects. I mean, you code something like you
41:34
Speaker 1: code a ceramic with something no. No, you add like
41:38
Speaker 1: a new kind of material inside the lattice, so that
41:40
Speaker 1: inside the crystal lattice you have, like you know, some
41:43
Speaker 1: other element that's occupying some of these things, and it
41:45
Speaker 1: changes the behavior of the electrons, forcing them, for example,
41:49
Speaker 1: spin locking them, forcing them to move in these circles
41:51
Speaker 1: without having a powerful magnetic field. Currently. Of course, it
41:54
Speaker 1: takes sort of complex machinery to fabricate these things, to
41:57
Speaker 1: make these mixtures. But you know, if you find one
42:00
Speaker 1: that's especially useful, especially powerful. I'm sure we'll come up
42:03
Speaker 1: with ways to mass produce them. I see, they're not
42:06
Speaker 1: super easy to make yet. Yeah, they're not super easy
42:09
Speaker 1: to make yet. But that's true of almost everything, right,
42:10
Speaker 1: you know, Like the first transistor was not simple or small, right, right,
42:14
Speaker 1: And they've gotten smaller and smaller. But now we're sort
42:16
Speaker 1: of reaching the limits of what we can do even
42:18
Speaker 1: with silicon and these crazy powerful ways to make tiny chips. Like,
42:23
Speaker 1: we're reaching a limit, and we're going to need something
42:26
Speaker 1: new for want to make things even smaller and more powerful.
42:28
Speaker 1: That's right, we're very used to Our computer is getting
42:30
Speaker 1: more powerful and smaller every single year. There's More's law
42:34
Speaker 1: where computing power doubles every eighteen months because we can
42:38
Speaker 1: make smaller transistors. But there is a limit there, right.
42:40
Speaker 1: If silicon gets too small, then it loses these properties,
42:44
Speaker 1: it's conductivity and its resistance, and we're pushing up against
42:47
Speaker 1: that limit. So people are working hard to find new
42:49
Speaker 1: materials that we can use to print these transistors. So
42:52
Speaker 1: it's a good time to discover that there's a whole
42:55
Speaker 1: new class of stuff out there that we can design
42:58
Speaker 1: and build that has weird new properties, right, right, to
43:00
Speaker 1: make phones even smaller and you know, higher resolution, and
43:06
Speaker 1: to make your batteries last longer. Oh that's right. Yeah,
43:08
Speaker 1: if they're more conductive, then you're not wasting as much
43:11
Speaker 1: energy into into heat, right. Yeah. Every time you feel
43:14
Speaker 1: your phone get hot, that's energy from your battery that
43:16
Speaker 1: could have been used to play your Netflix show but
43:19
Speaker 1: is instead is heating up your pocket. But that's just
43:21
Speaker 1: for regular computers that we know. Now, you could also
43:24
Speaker 1: use these new materials for a whole new kind of computer,
43:28
Speaker 1: that's right. We think that they might be excellent as
43:30
Speaker 1: a sort of base material out of which to build
43:33
Speaker 1: quantum computers. Quantum computers, remember, don't have this sort of
43:36
Speaker 1: normal switches that classical computers have, like that are either
43:40
Speaker 1: one or zero. They have these things inside them called cubits,
43:44
Speaker 1: which are in a quantum state superposition of ones and
43:47
Speaker 1: zeros with various probabilities. And these quantum computers are really
43:50
Speaker 1: fascinating and have some interesting potential to solve some weird problems.
43:54
Speaker 1: But one of the obstacles to building quantum computers is
43:57
Speaker 1: error correction. These quantum computer is gonna be a little
44:00
Speaker 1: bit noisy and a little bit fuzzy, and you don't
44:02
Speaker 1: always get the answer out that you want. And so
44:04
Speaker 1: they have all these complicated error correcting devices that get
44:08
Speaker 1: more and more laborious, more and more difficult as you
44:10
Speaker 1: get bigger and more powerful computers, which is one reason
44:13
Speaker 1: why we've only ever seen quantum computers with like ten
44:16
Speaker 1: bits or twenty bits, whereas, for example, you know your
44:19
Speaker 1: phone has megabits and megabits inside of it. We think
44:22
Speaker 1: that potentially these topological materials might have the right ingredients
44:27
Speaker 1: to be sort of self correcting. They might be able
44:30
Speaker 1: to develop cubits that automatically correct themselves, right Like if
44:34
Speaker 1: there's an error somehow, that error disappears somehow by itself,
44:38
Speaker 1: and it comes from the way that the electrons flow
44:40
Speaker 1: in these materials. They're actually sort of symmetries that preserve
44:44
Speaker 1: the electrons in these quasi particles. Remember we talked once
44:47
Speaker 1: about what quasi particles are. Like the way we think
44:49
Speaker 1: of photons as excitations in the electromagnetic field, you can
44:54
Speaker 1: also think about other fields fields inside materials and having
44:58
Speaker 1: energy stored inside those yields. So, for example, like a
45:01
Speaker 1: vibration inside a material, you think of that as like
45:04
Speaker 1: a phone on like a basic element of the vibration
45:08
Speaker 1: field inside a material. So some of these topological materials
45:11
Speaker 1: have these symmetries that preserve these quasi particles that allow
45:15
Speaker 1: you to build basically self error correcting quantum bits. I see. Yeah,
45:20
Speaker 1: because these kinds of like new kinds of quasi particles
45:23
Speaker 1: can only happen under special conditions like what you get
45:27
Speaker 1: with these topological materials exactly, and the topological nature of
45:32
Speaker 1: them preserves these symmetries that it forces them to act
45:35
Speaker 1: in certain ways, and those ways help prevent errors from
45:38
Speaker 1: cropping up and correct them when they do. Right, Because
45:41
Speaker 1: right now, to make a quantum computer, you need like
45:42
Speaker 1: these extreme machines, right, you need like a machine the
45:45
Speaker 1: size of a room just to have ten cubits. But
45:47
Speaker 1: if you can somehow use these tiny materials, then you
45:51
Speaker 1: might get a quantum computer in your pocket. Yes, you're right,
45:54
Speaker 1: you might, and they might be self air correcting, so
45:57
Speaker 1: you wouldn't need this like really complicated devices to help
46:00
Speaker 1: fix the errors from ten or twenty bits. Currently, the
46:03
Speaker 1: error rate grows very rapidly as you add quantum bits,
46:07
Speaker 1: and so if they're self air correcting, that might solve
46:09
Speaker 1: that problem. But that's sort of like potential. That's something
46:11
Speaker 1: people are exploring. But you know, the flavor of it
46:14
Speaker 1: is that we have a new kind of material and
46:16
Speaker 1: we don't even really know what it can do. Somebody's
46:19
Speaker 1: gonna come along next year or the year after and
46:22
Speaker 1: come up with a crazy idea for how you can
46:24
Speaker 1: put these things together to make something nobody's ever imagined.
46:28
Speaker 1: I see, because it's like opened up a whole new
46:30
Speaker 1: kinds of behaviors of matter that we didn't know before exactly,
46:34
Speaker 1: Like all the complicated behavior of matter that you're familiar
46:36
Speaker 1: with is an emergent phenomena from putting together in complex ways,
46:40
Speaker 1: and now we know there are a whole new areas.
46:42
Speaker 1: Like imagine if nobody had ever seen a conductor before,
46:44
Speaker 1: we only ever had insulators, and then you showed up
46:46
Speaker 1: with this material that can like zap people and transmit
46:49
Speaker 1: energy and you know, create these arcs through the area, Like,
46:52
Speaker 1: oh my gosh, it's like magic. This is like that
46:54
Speaker 1: moment when somebody's come up with something new. It's not
46:56
Speaker 1: exactly a conductor, not exactly insulators, something new and weird
47:00
Speaker 1: can do new stuff. And so you know what it's
47:02
Speaker 1: going to be able to accomplish might seem like magic
47:04
Speaker 1: to us today. Wow, interesting, in the future will be
47:08
Speaker 1: like this ice cream taste amazing? What is it? It's
47:11
Speaker 1: a topological material. Topological mint chip is so much better
47:16
Speaker 1: than classical mint chip. Oh my god, yeah, it's it
47:19
Speaker 1: has a mint que chips. And you're like, oh my goodness,
47:22
Speaker 1: I can't believe most humans have never tasted a mint
47:25
Speaker 1: que chip. What a tragedy. What do it even mean
47:27
Speaker 1: to be human before that was invented? Right? Like, were
47:30
Speaker 1: they even really fully aware? Life really started when quantum
47:33
Speaker 1: ice cream was invented. That's what the aliens are waiting for,
47:36
Speaker 1: for us to achieve that level of technology before they
47:38
Speaker 1: come and visit us. Oh, I see, because they don't
47:41
Speaker 1: want to go anywhere that doesn't have these quantum mint
47:43
Speaker 1: ke chips. It's like, you don't want to go to
47:45
Speaker 1: that place if it doesn't have bathroom that what kind
47:49
Speaker 1: of occasion is that? All? Right? Well, again, I think
47:52
Speaker 1: this isn't an exciting thing because it feels like, you know,
47:55
Speaker 1: we're learning all the time that there are new things
47:58
Speaker 1: yet to be discovered in this universe, new even new
48:01
Speaker 1: kinds of material and new kinds of matter that we
48:03
Speaker 1: can potentially engineer amazing new devices out of. That's right,
48:07
Speaker 1: So we have not just revolutions in our basic understanding
48:10
Speaker 1: of the fundamental particles and what the universe is. We
48:13
Speaker 1: also have revolutions all the time in how those bits
48:17
Speaker 1: fit together to make weird kinds of stuff that exist
48:20
Speaker 1: at our scale. So our understanding the universe is constantly transforming,
48:24
Speaker 1: and there are enormous opportunities out there for people to
48:26
Speaker 1: make discoveries. So you young scientists out there, seven, eight,
48:29
Speaker 1: ten years old, fifteen years old, you can still revolutionize
48:33
Speaker 1: our understanding of the universe. There's so much left to do.
48:37
Speaker 1: But if you're sixteen, it's over for you, right, is
48:39
Speaker 1: that what you're saying in But no, I mean anything
48:42
Speaker 1: could come up of anyone of any age, right, Yes, absolutely,
48:45
Speaker 1: sixteen year olds could totally revolutionized the universe. I don't
48:48
Speaker 1: know a seventeen eighteen and any universe whited. No, it's
48:52
Speaker 1: it's open for everybody. Absolutely, a non exhaustive list of
48:54
Speaker 1: example ages. Ask yourself, do you want to be in
48:57
Speaker 1: the group of humans that have never seen these revolutions
48:59
Speaker 1: or do you want to be in the group of humans,
49:01
Speaker 1: the future, humans that know these amazing things. All right, Well,
49:05
Speaker 1: we hope you enjoyed d and it blew your mind
49:08
Speaker 1: a little bit, at least on the surface. Thanks for
49:10
Speaker 1: joining us, See you next time. Thanks for listening, and
49:21
Speaker 1: remember that Daniel and Jorge explained the universe is a
49:23
Speaker 1: production of I Heart Radio. For more podcast from my
49:27
Speaker 1: Heart Radio, visit the i Heart Radio app, Apple Podcasts,
49:31
Speaker 1: or wherever you listen to your favorite shows. H