Breakthrough Quantum Material Conducts Electricity With Zero Energy Loss

<v Speaker 1>Welcome to the quart Side Quantum Physics Podcast, an exploration
<v Speaker 1>of the fundamental structure of reality, where quantum laws govern matter, energy,
<v Speaker 1>and information. Here, uncertainty is a feature, not a flaw,
<v Speaker 1>and understanding begins at the smallest scales.
<v Speaker 2>Hello everyone, and welcome back. It is Thursday, February twelfth,
<v Speaker 2>twenty twenty six. I want to start today's exploration with
<v Speaker 2>a feeling, a sensation that I guarantee every single one
<v Speaker 2>of you has felt. It's that very specific kind of annoyance.
<v Speaker 2>You're sitting there, maybe you're on a long video call,
<v Speaker 2>or you're rendering a video, or maybe you're just you know,
<v Speaker 2>scrolling on your phone with the brightness all the way up,
<v Speaker 2>and then you feel it, the heat, the heat. Your
<v Speaker 2>phone starts to feel like a hot little brick. Your
<v Speaker 2>laptop fan suddenly kicks in, and it's like a tiny
<v Speaker 2>jet engine is about to take off from your desk.
<v Speaker 3>And your battery percentage just plummets.
<v Speaker 2>It's just nose dives. Yeah, and we treat this as normal.
<v Speaker 2>We just think, oh, my device is working hard. But
<v Speaker 2>when you really stop and think about the physics of it, yeah,
<v Speaker 2>that heat is just failure, isn't it.
<v Speaker 3>It's pure failure. It is waste. In physics, we call
<v Speaker 3>it dissipation. And it is, without a doubt, the single
<v Speaker 3>biggest bottleneck in modern electronics.
<v Speaker 2>So that heat is just energy that's not doing what
<v Speaker 2>I wanted to do exactly.
<v Speaker 3>That heat is literally your batteries, precious energy being turned
<v Speaker 3>into useless themal vibration. Instead of you know, running the
<v Speaker 3>app you just opened, it's just gone.
<v Speaker 2>It's like paying for a gallon of gas and just
<v Speaker 2>pour and have it in the ground before you even
<v Speaker 2>start the car. So the reason we're talking about this,
<v Speaker 2>this very fundamental problem, is because of a paper that
<v Speaker 2>just dropped, I mean just dropped two days ago February tenth,
<v Speaker 2>twenty twenty six in the journal Nature Physics. It's from
<v Speaker 2>a team at the University of Washington led by researcher
<v Speaker 2>name Shaodong Shoo.
<v Speaker 3>And it is a monster of a paper, truly, it
<v Speaker 3>really is.
<v Speaker 2>Because they are claiming to have well essentially solved the
<v Speaker 2>heat problem. Yeah, and not in some small incremental we
<v Speaker 2>made the copper wiring slightly better kind of way.
<v Speaker 3>So this is a fundamental shift.
<v Speaker 2>They have engineered a material where electricity flows with zero
<v Speaker 2>heat loss.
<v Speaker 3>Effectively zero no dissipation. It is the first practical, verified
<v Speaker 3>realization of what's called a dissipationless fractional churn insulator.
<v Speaker 2>Okay, dissipationless fractional churn insulator. That's a mouthful. I feel
<v Speaker 2>like we need to put a giant pin in that
<v Speaker 2>phrase because there is a lot of physics jargon packed
<v Speaker 2>into those forwards. There is will unpack it all you will,
<v Speaker 2>but the headline, the big takeaway here is that they
<v Speaker 2>have created a state of matter where electrons just flow
<v Speaker 2>without resistance. And this is the kicker. They've done it
<v Speaker 2>without the massive, room sized magnetic fields that you usually
<v Speaker 2>need for this kind of quantum magic, and.
<v Speaker 3>That is the holy part of this. We've known about
<v Speaker 3>zero resistance states for a long time, but they always
<v Speaker 3>always required these insane lab conditions that made them totally
<v Speaker 3>impractical for say a microchip. Right this paper, it completely
<v Speaker 3>changes the playing field.
<v Speaker 2>So here's our roadmap for this analysis. Yeah, first we
<v Speaker 2>have to start with the physics of the impossible. You know,
<v Speaker 2>how do you even get electrons to stop bumping into things?
<v Speaker 2>We need to talk about this whole family of quantum hall.
<v Speaker 3>Effects, right, the basics.
<v Speaker 2>Then we need to get into the drama of the engineering,
<v Speaker 2>because this isn't the first time this team has tried this.
<v Speaker 2>They actually took a swing at it back in twenty
<v Speaker 2>twenty three and it didn't quite work.
<v Speaker 3>It was a fascinating failure, though, one of those successful
<v Speaker 3>failures that pushes science forward exactly.
<v Speaker 2>So we'll talk about what went wrong then and the
<v Speaker 2>incredibly specific, almost artisanal changes they made to the crystal
<v Speaker 2>growth and this twisting mechanism to finally make it work
<v Speaker 2>this year.
<v Speaker 3>And then there's the mystery.
<v Speaker 2>Yes, we have to talk about the mystery, because there's
<v Speaker 2>a section at the end of this paper that base
<v Speaker 2>sickly says, Okay, we built it. It works perfectly, but
<v Speaker 2>now it's behaving in a way that makes absolutely no
<v Speaker 2>sense to us.
<v Speaker 3>The thermal activation gap mystery. It's a genuine plot twist
<v Speaker 3>in the data.
<v Speaker 2>So let's dive in section one, the physics of the impossible.
<v Speaker 2>I want you to explain resistance to me, like I'm well,
<v Speaker 2>let's say a smart high school student, Why does my
<v Speaker 2>fane get hot? What is actually happening at the atomic level?
<v Speaker 3>Okay? Sure, To really get resistance, you have to visualize
<v Speaker 3>the life of a single electron trying to get through
<v Speaker 3>a wire. We have this mental picture of electricity as
<v Speaker 3>like water flowing smoothly through a pipe, a.
<v Speaker 2>Nice, clean, continuous stream, right.
<v Speaker 3>But at the atomic level, a copper wire is a
<v Speaker 3>complete nightmare. It is a chaotic, crowded, messy obstacle course.
<v Speaker 2>So the electron isn't just gliding along, not.
<v Speaker 3>At all, not even close. Imagine you're on a highway,
<v Speaker 3>but this highway has no lanes, no speed limit, and
<v Speaker 3>it's just filled with giant, vibrating boulders. The boulders are
<v Speaker 3>the atoms of the copper and the highway is also
<v Speaker 3>full of other cars, which are all the other electrons.
<v Speaker 3>The electron hits the gas that's the voltage you apply,
<v Speaker 3>and it zooms forward, but almost immediately whack it smacks
<v Speaker 3>into an impurity in the metal. It recovers, zooms again, Whack,
<v Speaker 3>it hits an atom that's just vibrating because of temperature.
<v Speaker 3>It recovers again, whack, it collides with another electron.
<v Speaker 2>In every single one of those collisions, that's the heat.
<v Speaker 3>That is the heat precisely in physics we call it scattering.
<v Speaker 3>The electron has kinetic energy, energy of motion. When it
<v Speaker 3>crashes into an atom, it transfers some of that energy,
<v Speaker 3>making the atom vibrate even more violently. That collective violent
<v Speaker 3>vibration of all the atoms is what we feel and
<v Speaker 3>measure as heat. So resistance is really just a measure
<v Speaker 3>of how often your electrons are crashing.
<v Speaker 2>It's friction, It's electrical friction.
<v Speaker 3>It is the exact same principle. Now, for decades, physicists
<v Speaker 3>have been absolutely obsessed with one question, how do we
<v Speaker 3>stop the crashing? How can we build a highway where
<v Speaker 3>it's physically impossible for the electrons to hit anything?
<v Speaker 2>Which sounds well impossible, and that brings us to the
<v Speaker 2>quantum hall effect. Okay, I've heard this term thrown around
<v Speaker 2>usually when people are talking about Nobel prizes, but what
<v Speaker 2>is it actually?
<v Speaker 3>Okay, so let's take that chaotic highway, your normal copper wire.
<v Speaker 3>The first thing we do is we cool it way
<v Speaker 3>way down to near absolute zero, so.
<v Speaker 2>Like a few degrees above the coldest possible temperature in.
<v Speaker 3>The universe exactly. That slows down the vibrating atoms. It's
<v Speaker 3>like clearing most of the boulders off the road. The
<v Speaker 3>road is now much smoother, Okay.
<v Speaker 2>Smooth road. But the electrons the other cars are still there.
<v Speaker 2>They can still crash into each other.
<v Speaker 3>They can. So next we turn on a magnet, and
<v Speaker 3>not just any magnet, a massive magnet. We're talking about
<v Speaker 3>magnetic fields of ten, maybe twenty tesla. These are monsters.
<v Speaker 2>Just for context, a hospital MRI machine is what one
<v Speaker 2>point five or maybe three tesla.
<v Speaker 3>Right, So we were talking about fields that would rip
<v Speaker 3>a metal chair across the room. It's an incredibly strong field. Now,
<v Speaker 3>when you apply that kind of magnetic force perpendicular to
<v Speaker 3>an electron's motion, the electrons path curves.
<v Speaker 2>It doesn't go straight anymore, it can't.
<v Speaker 3>The field forces it to move in a circle. This
<v Speaker 3>is a fundamental principle called cyclotron motion.
<v Speaker 2>So now instead of all the cars driving straight down
<v Speaker 2>the highway, they're all just driving in tiny little circles
<v Speaker 2>in place that doesn't seem very useful.
<v Speaker 3>In the middle of the material, what we call the bulk, yes,
<v Speaker 3>they're just spinning in pla is completely trapped going nowhere.
<v Speaker 3>But think about what happens at the very edge of
<v Speaker 3>the material. Think about the guard rail on the side
<v Speaker 3>of the highway.
<v Speaker 2>Okay, so I'm an electron near the edge. I try
<v Speaker 2>to spin in a circle to my right, but before
<v Speaker 2>I can complete the circle, I hit the wall.
<v Speaker 3>You hit the wall, so you bounce off it. You
<v Speaker 3>try to spin again, You hit the wall again, You
<v Speaker 3>bounce again. What ends up happening is this beautiful skipping motion.
<v Speaker 3>The electrons skip jump along the boundary of the material.
<v Speaker 2>Okay, I can picture that.
<v Speaker 3>And here is the magic part. Because the magnetic field
<v Speaker 3>forces everything to try and turn, let's say to the right,
<v Speaker 3>all the electrons on that one edge are forced to
<v Speaker 3>move in exactly the same direction.
<v Speaker 2>It creates a one way street.
<v Speaker 3>A perfect one way dissipationless super highway. There's no oncoming traffic.
<v Speaker 3>An electron can't scatter backwards because to do that, it
<v Speaker 3>would have to turn left, and the magnetic field makes
<v Speaker 3>that physically impossible.
<v Speaker 2>So it literally can't crash.
<v Speaker 3>It can't. And this is what we call a topological
<v Speaker 3>property topology.
<v Speaker 2>That's the branch of math about shapes. Right, the whole
<v Speaker 2>donut and coffee mug thing exactly.
<v Speaker 3>In topology, a coffee mug and a doughnut are considered
<v Speaker 3>the same because they both have one hole. You can
<v Speaker 3>squish and stretch one into the other. Without tearing it.
<v Speaker 3>In the quantum Hall effect, the flow of electrons along
<v Speaker 3>the edge is protected by the topology of the system's
<v Speaker 3>quantum state.
<v Speaker 2>So even if there's a bump, like a defect in
<v Speaker 2>the material.
<v Speaker 3>The electron just flows smoothly around it. It can't scatter backwards.
<v Speaker 3>It's robust. The resistance along that edge just vanishes. It
<v Speaker 3>goes to zero.
<v Speaker 2>Wow.
<v Speaker 3>And when you measure it, the Hall resistance doesn't increase smoothly.
<v Speaker 3>It goes up in these perfect quantized steps, like a staircase,
<v Speaker 3>step one, step two. It's this beautiful, perfect order emerging
<v Speaker 3>from total chaos.
<v Speaker 2>Okay, so that's the quantum Hall effect that the paper
<v Speaker 2>we're discussing today. It's not just about that. It's about
<v Speaker 2>the fractional quantum Hall effect. And this is where my
<v Speaker 2>brain starts to hurt a little bit. How can you
<v Speaker 2>have a fraction of a step? How on Earth can
<v Speaker 2>you have a fraction of an electron?
<v Speaker 3>This is one of the coolest, most mind bending concepts
<v Speaker 3>in all of physics. And you're right. An electron is
<v Speaker 3>a fundamental particle. It's an elementary particle. You can't take
<v Speaker 3>a tiny knife and slice it into thirds, right, but
<v Speaker 3>you can get a group of electrons to act collectively
<v Speaker 3>as if they are fractional particles.
<v Speaker 2>Okay, explain that what does that even mean?
<v Speaker 3>It all comes down to collective behavior. Think about it
<v Speaker 3>like this. Imagine you're in a crowded room. If everyone
<v Speaker 3>is just milling about randomly, you just have a collection
<v Speaker 3>of individuals. But what if everyone links arms and starts
<v Speaker 3>moving together in a very specific, comp plex braided dance.
<v Speaker 2>Then the crowd itself becomes a thing. The entity is
<v Speaker 2>the pattern of the dance, not the individual person.
<v Speaker 3>That's a perfect way to put it. In the fractional
<v Speaker 3>quantum Hall effect or FQHG, the conditions are so extreme,
<v Speaker 3>the magnetic field is even stronger, the material is even cleaner,
<v Speaker 3>that the electrons can't ignore each other anymore. Their mutual
<v Speaker 3>repulsion becomes the dominant force. There's force to interact intensely.
<v Speaker 3>They organize themselves into this incredibly delicate correlated quantum liquid.
<v Speaker 2>A liquid made of electrons, a.
<v Speaker 3>Quantum liquid, yes, And the tiny ripples in this liquid,
<v Speaker 3>the little vortices or excitations they behave mathematically exactly like
<v Speaker 3>particles with a fractional charge, like one third of an electrons.
<v Speaker 2>Chart or two thirds, so we're not splitting the particle.
<v Speaker 2>We are creating a quasi particle out of the collective
<v Speaker 2>dance of the crowd.
<v Speaker 3>You've nailed it. That's the can reuse. These are quasi particles.
<v Speaker 3>They're often called enians, and they are incredibly important for
<v Speaker 3>the future of technology. Why because they're stable, because they're topological.
<v Speaker 3>They're born out of this global collective dance, which makes
<v Speaker 3>them super robust. If you poke one individual electron, the
<v Speaker 3>overall dance just continues. The fractional quasi particle remains intact.
<v Speaker 2>And this is the link to quantum computing, right, This
<v Speaker 2>is why everyone gets so excited.
<v Speaker 3>This is the holy grail of quantum computing. A normal
<v Speaker 3>quantum bit aquibit is ridiculously fragile. The slightest vibration a
<v Speaker 3>little bit of heat, and the quantum information is lost.
<v Speaker 3>It's called decoherence. But if you could build a quibit
<v Speaker 3>out of these fractional stakes bulletproof, it would be topologically protected.
<v Speaker 3>The idea is you could literally braid these quasi particles
<v Speaker 3>around each other to perform calculations, and because the information
<v Speaker 3>is stored in the global topology of the braid local
<v Speaker 3>noise couldn't mess it up.
<v Speaker 2>So a fault tolerant quantum computer.
<v Speaker 3>The dream of a fault tolerant quantum computer.
<v Speaker 2>Yes, okay, so let's just recap the stakes here. We
<v Speaker 2>want this fractional quantum hall state because it's dissipationless, no heat,
<v Speaker 2>and it's topologically stable, which is great for computing. But
<v Speaker 2>there has always been this one giant show stoffing catch
<v Speaker 2>the magnet, the giant room size credit card erasing magnet.
<v Speaker 3>Exactly, you cannot put a fifteen tesla magnet inside your iPhone.
<v Speaker 3>It's just not going to happen. So for forty years
<v Speaker 3>this has been this beautiful laboratory curiosity. Look what amazing
<v Speaker 3>things nature can do. Moment, but not a Let's build
<v Speaker 3>a product with this moment.
<v Speaker 2>Which brings us to the churn insulator. This is the
<v Speaker 2>proposed solution to the magnet problem, at least in theory.
<v Speaker 3>In theory, yes, a churn insulator is a type of
<v Speaker 3>material that, through its own internal quantum mechanics, essentially creates
<v Speaker 3>its own magnetic environment. The specific arrangement of the atoms
<v Speaker 3>and the way the electrons wave functions interact. It generates
<v Speaker 3>an effective magnetic field.
<v Speaker 2>So it's like virtual reality for electrons. They think they're
<v Speaker 2>in a massive magnetic field. Yeah, so they start doing
<v Speaker 2>the quant the Hall dance even though there's no external magnet.
<v Speaker 3>That is a fantastic analogy. Yes, a property of the
<v Speaker 3>material's electronic structure called Barry curvature acts just like a
<v Speaker 3>magnetic field. So you get the protected edge states, you
<v Speaker 3>get the one way super highway, you get the zero
<v Speaker 3>resistance all at zero external magnetic field.
<v Speaker 2>And that's the anomalous part of the name quantum anomalous
<v Speaker 2>Hall effect anomalists because the magnet is missing.
<v Speaker 3>Correct. So bringing it all back to this week's paper,
<v Speaker 3>Sue and his team have been chasing the ultimate prize,
<v Speaker 3>not just a quantum anomalous Hall effect, but a fractional
<v Speaker 3>quantum anomalist Hall effect.
<v Speaker 2>Right. They want the material that has the fractional charges,
<v Speaker 2>the one third steps and works with no magnet.
<v Speaker 3>That is the goal, a dissipationless fractional churn insulator.
<v Speaker 2>And they actually tried to publish this before, didn't they.
<v Speaker 2>I was looking at the timeline back in twenty twenty three.
<v Speaker 2>They had a paper that claimed they found it, but
<v Speaker 2>looking back now, it seems like that was a close
<v Speaker 2>but no cigar moment.
<v Speaker 3>Oh, it was a heartbreaking moment for the field. Honestly, Ujin,
<v Speaker 3>you're a scientist. You spend years designing and building this
<v Speaker 3>incredibly complex device. Cool it down. You measure it, and
<v Speaker 3>you see it. You see the plateau and the Hall
<v Speaker 3>resistance that screams one third fractional charges here.
<v Speaker 2>You pop the fambage, you.
<v Speaker 3>Pop the champagne. But then then you look at the
<v Speaker 3>other measurement. You measure the longitudinal resistance.
<v Speaker 2>Okay, remind us again. Hall resistance is the measurement across
<v Speaker 2>the current, the one that gives you the nice steps.
<v Speaker 3>Longitudinal resistance is it's the resistance along the direction of
<v Speaker 3>the current flow. In a perfect dissipationless state. This number
<v Speaker 3>should be zero, a flat line at the bottom of
<v Speaker 3>your graph, no question.
<v Speaker 2>And in their twenty twenty three experiment.
<v Speaker 3>It wasn't zero. It was something. It was small, but
<v Speaker 3>it was definitely measurably not zero.
<v Speaker 2>So the pipe was leaky.
<v Speaker 3>The pipe was leaky, exactly. They had the right general idea.
<v Speaker 3>The electrons were trying to do the collective dance, but
<v Speaker 3>the dance floor was too messy. They were tripping. They
<v Speaker 3>were bumping into things. Energy was leaking out as heat.
<v Speaker 3>It was not dipationless.
<v Speaker 2>I imagine for a physicist in this field, kind of
<v Speaker 2>dissipationless is like being kind of pregnant. It's a binary thing.
<v Speaker 2>It's either zero or it isn't.
<v Speaker 3>Absolutely in this game, if there's any resistance, it means
<v Speaker 3>the topological protection is broken. It means there are what
<v Speaker 3>we call dissipative channels that the electrons are finding. So
<v Speaker 3>for the last three years, big question in the community
<v Speaker 3>hasn't been is the theory wrong? The question has been
<v Speaker 3>is our sample just too dirty?
<v Speaker 2>Too dirty? I love that we're talking about the most
<v Speaker 2>esoteric quantum mechanics imaginable, and the problem comes down to
<v Speaker 2>basically dirt.
<v Speaker 3>Atomic scale dirt disorder in the crystal.
<v Speaker 2>Okay, so let's move on to that section three engineering
<v Speaker 2>the solution. How did they clean up the dirt? Because
<v Speaker 2>this is where the story shifts from abstract physics to
<v Speaker 2>really hardcore hands on material science. It really does They
<v Speaker 2>used of material called molybdenum detailur ride or multi two
<v Speaker 2>to two? Why this particular stuff? Why not good Old's silk?
<v Speaker 3>Well, silicon is great for what it does, but it's
<v Speaker 3>electronically kind of boring for this kind of work. MOTI
<v Speaker 3>two to two is part of a class of materials
<v Speaker 3>called transition metal decocogenis or TMDs, And the key thing
<v Speaker 3>about them is that they're layered materials like graphite. You
<v Speaker 3>can literally peel them apart into sheets that are just
<v Speaker 3>a few atoms thick.
<v Speaker 2>So they're effectively two dimensional.
<v Speaker 3>Exactly two D. And the real magic happens when you
<v Speaker 3>take two of these atomically thin sheets and stack them
<v Speaker 3>on top of each other. But you don't just stack
<v Speaker 3>them like two pieces of paper. You twist them.
<v Speaker 2>This is the famous tristronics.
<v Speaker 3>This is twistronics. It sounds like a nineteen eighties dance move,
<v Speaker 3>but it's one of the hottest fields in physics right now.
<v Speaker 3>When you rotate that top layer relative to the bottom
<v Speaker 3>layer by a very specific tiny angle, in this case
<v Speaker 3>somewhere around three degrees, you create something called a more pattern.
<v Speaker 2>I've seen this in the real world. If you look
<v Speaker 2>through two layers of fine mash, like two window screens,
<v Speaker 2>and you move your head, you see these weird, bigger,
<v Speaker 2>wavy patterns that aren't in the original mesh.
<v Speaker 3>Yes, that is an optical more pattern. In these stacked crystals,
<v Speaker 3>the twisting creates an electronic maree pattern. It's a giant
<v Speaker 3>periodic superlattice for the electrons, and this pattern fundamentally changes
<v Speaker 3>the energy landscape they live in. It creates what physicists
<v Speaker 3>call flat bands.
<v Speaker 2>Okay, flat bands, This feels like a key concept. We
<v Speaker 2>really need to nail down. What does a flat energy
<v Speaker 2>band do to an electron? Right?
<v Speaker 3>So, in a normal material, the energy band is curved.
<v Speaker 3>That means an electron can have a wide range of
<v Speaker 3>kinetic energies. It can zoom around at all.
<v Speaker 2>Different speeds, free to move.
<v Speaker 3>It's free to move, and it's kinetic energy dominates its life.
<v Speaker 3>It's running around so fast that it doesn't really have
<v Speaker 3>time to interact or care about the electron next to it.
<v Speaker 2>Too busy running to chat with the neighbors.
<v Speaker 3>Exactly. But in a flat band, the more superlattice essentially
<v Speaker 3>traps the electrons. It dramatically quenches or flattens their kinetic energy.
<v Speaker 3>They slow down to a crawl. They all have roughly
<v Speaker 3>the same very low energy, and because they aren't zooming
<v Speaker 3>around anymore, suddenly the most important force in their life
<v Speaker 3>isn't their own speed, it's the electrostatic repulsion from all
<v Speaker 3>their neighbors.
<v Speaker 2>The chat with the neighbors becomes the loudest thing in
<v Speaker 2>the room.
<v Speaker 3>The interaction energy becomes dominant, and that is the absolute
<v Speaker 3>prerequisite for the fractional quantum hall state. You need strong
<v Speaker 3>interactions to force the electrons into that collective correlated dance.
<v Speaker 3>The twist creates the flat band, and the flat band
<v Speaker 3>turns on the interactions.
<v Speaker 2>Okay, so they knew they need a twisted mo call
<v Speaker 2>two too. Back in twenty twenty three, they had that recipe.
<v Speaker 2>So what change between then and now? What was the
<v Speaker 2>big breakthrough?
<v Speaker 3>It was two things. First, they realized their starting ingredients,
<v Speaker 3>the crystals themselves, just weren't good enough. Even though they
<v Speaker 3>looked perfect under a normal microscope at the atomic level,
<v Speaker 3>they were full of defects the dirt. So they changed
<v Speaker 3>the recipe for how they grew the crystals. And this
<v Speaker 3>is where we have to give huge credit to the
<v Speaker 3>materials scientists on the team, specifically Ginhachu post doc Chohwehu.
<v Speaker 3>They switch to a different growth method called horizontal flux growth.
<v Speaker 2>How is that different from the usual way they make
<v Speaker 2>these things?
<v Speaker 3>Well, the more common way is something called chemical vapor transport.
<v Speaker 3>You basically heat up the raw powder, it turns into
<v Speaker 3>a gas, It drifts down a tube to a cooler spot,
<v Speaker 3>and it crystallizes on a surface. It's fast and it's
<v Speaker 3>pretty efficient, but it's a bit chaotic. Atoms can kind
<v Speaker 3>of slam into place. Sometimes they land in the wrong spot,
<v Speaker 3>creating a defect.
<v Speaker 2>It sounds like the fast food version of crystal growth.
<v Speaker 3>That's not a bad analogy. Horizontal flex growth is the
<v Speaker 3>slow cooked, artisanal, farm to table version. You dissolve the
<v Speaker 3>raw molybdenum and tellurium powder and a molten solvent, a
<v Speaker 3>liquid salt called a flux. It's a big liquid bath,
<v Speaker 3>and then you cool that entire bath down incredibly slowly.
<v Speaker 3>We are talking fractions of a degree over many hours
<v Speaker 3>or even days.
<v Speaker 2>It's like making perfectly clear ice for a fancy cocktail.
<v Speaker 2>If you freeze water really fast, it gets cloudy and
<v Speaker 2>full of imperfections. If you freeze is it super super slowly,
<v Speaker 2>it comes out crystal clear.
<v Speaker 3>That is the perfect analogy. By cooling it so slowly
<v Speaker 3>that atoms have time to find their absolute lowest energy position,
<v Speaker 3>they can wiggle around and slot themselves perfectly into the
<v Speaker 3>crystal lattice, no vacancies, no misaligned atoms, just perfection.
<v Speaker 2>And did it actually make a difference in the final product.
<v Speaker 3>A monumental difference. They measured a property called charge carrier mobility,
<v Speaker 3>which is basically a measure of how easily electrons can
<v Speaker 3>move through the material without scattering. It's a proxy for
<v Speaker 3>crystal quality. It increased by more than an order of magnitude,
<v Speaker 3>more than ten times better than the crystals they were
<v Speaker 3>using in twenty twenty three.
<v Speaker 2>Wow. All from just being more patient during the growth process.
<v Speaker 3>All from improving the fundamental ingredients. But that was only
<v Speaker 3>half the battle. You can have a perfect, flawless crystal,
<v Speaker 3>but you still have to perform the twist and the
<v Speaker 3>act of peeling, cutting and stacking these three atom thick
<v Speaker 3>layers is well, it's violent.
<v Speaker 2>I can't even imagine trying to twist some thing that
<v Speaker 2>thin without getting wrinkles and folds all over it.
<v Speaker 3>It's an absolute nightmare. And this was the second major
<v Speaker 3>problem in twenty twenty three twist angle disorder. Imagine you
<v Speaker 3>need that magic more pattern, which requires say exactly three
<v Speaker 3>point seven degrees of twist. But in the twenty twenty
<v Speaker 3>three devices, the twist angle wasn't uniform across the whole sample.
<v Speaker 3>One corner might have been at three point six degrees,
<v Speaker 3>the middle at three point seven, and the other corner at
<v Speaker 3>three point eight.
<v Speaker 2>So the flat band isn't actually flat everywhere it's warped.
<v Speaker 3>It's warped. The physics changes from one spot to the next.
<v Speaker 3>So an electron moving across the device hits these patches
<v Speaker 3>of the wrong angle and it scatters. It breaks the magic,
<v Speaker 3>it ruins the topological protection.
<v Speaker 2>So how did they iron out the wrinkles? Literally?
<v Speaker 3>A student on the team he on June Park gets
<v Speaker 3>the credit here. They refine the fabrication technique. They developed
<v Speaker 3>a new stamping method that uses specific polymers to handle
<v Speaker 3>the layers, reducing mechanical stress and ensuring the tension is
<v Speaker 3>perfectly uniform as the pop layer is laid down.
<v Speaker 2>So, okay, let's put it all together. They have the
<v Speaker 2>slow frozen eyes, ice perfect crystal, and they have the
<v Speaker 2>perfectly ironed out uniform twist. This is the twenty twenty
<v Speaker 2>six device. The moment of truth arrives.
<v Speaker 3>The moment of truth they put the new device in
<v Speaker 3>the cryostat, they cool it down to base temperature just
<v Speaker 3>millikelvin above absolute zero. They apply the gate voltage to
<v Speaker 3>tune the electron density to exactly two thirds filling.
<v Speaker 2>Why two thirds specifically.
<v Speaker 3>That just happens to be one of the known sweet
<v Speaker 3>spots where these fractional states are predicted to be most stable.
<v Speaker 3>It means, for every three units of magnetic flux in
<v Speaker 3>the Maire super lattice, you have two electrons. It's a
<v Speaker 3>particular stable configuration for the dance.
<v Speaker 2>Okay, two thirds filling. They flip the switch, they start
<v Speaker 2>measuring the resistance.
<v Speaker 3>What happens, The hall resistance jumps up and forms a
<v Speaker 3>perfect quantized placateau, exactly where theory says the two thirds
<v Speaker 3>fractional state should be. That's the good news, same.
<v Speaker 2>As twenty twenty three so far. But what about the
<v Speaker 2>other one, the longitudinal resistance, the heat loss.
<v Speaker 3>It drops to zero, a flat line, fixed flat line.
<v Speaker 3>It vanishes into the noise floor of their measurement equipment.
<v Speaker 3>In the twenty twenty three paper, there was a clear bump,
<v Speaker 3>a peak of resistance there. In the twenty twenty six paper,
<v Speaker 3>it is a beautiful flat line at.
<v Speaker 2>Zero they did it. A dissipationless fractional churn insulator.
<v Speaker 3>They did it, and the significance of this really cannot
<v Speaker 3>be overstated. They have proven definitively that you do not
<v Speaker 3>need an external magnetic field to get this exotic quantum state.
<v Speaker 3>They've proven that the key variable was always material quality.
<v Speaker 2>It validates the entire field of twistronics completely.
<v Speaker 3>It shows that by engineering these more a patterns, we
<v Speaker 3>can create and control some of the most bizarre and
<v Speaker 3>wonderful phases of matter imaginable.
<v Speaker 2>So if I'm a listener at home, I'm probably asking, Okay,
<v Speaker 2>this is super cool physics, but when does this get
<v Speaker 2>into my laptop and stop it from burning my legs?
<v Speaker 3>Well, we should be clear there are still some major hurdles.
<v Speaker 3>The biggest one is temperature.
<v Speaker 2>Right, this is still all happening at near absolute zero.
<v Speaker 3>It is we are not at room temperature yet, but
<v Speaker 3>the size of the energy gap they measured is promising.
<v Speaker 3>It suggests that with further improvements we could push that
<v Speaker 3>operating temperature up. But the more immediate application isn't about
<v Speaker 3>power lines or laptops, not yet.
<v Speaker 2>It's the quantum computer.
<v Speaker 3>It's the quantum computer. Remember the braiding the enions.
<v Speaker 2>The topologically protected quivots.
<v Speaker 3>Yes, now that we have a physical platform where these
<v Speaker 3>enians demonstrably exist without needing a giant magnet, we can
<v Speaker 3>start to actually design circuits. You could, in principle, etch
<v Speaker 3>tiny pathways on this Maditude two chip and use electric
<v Speaker 3>fields to shuttle these fractional quasi particles around, braid them
<v Speaker 3>around each other, and perform a computation.
<v Speaker 2>A computation that doesn't just collapse into dust when you
<v Speaker 2>look at.
<v Speaker 3>It's funny exactly. This transforms topological quantum computing from a
<v Speaker 3>beautiful theory on a blackboard into a tangible hardware platform.
<v Speaker 3>It's a chip, it exists, it's sitting in a lab
<v Speaker 3>in Seattle right now.
<v Speaker 2>That is just incredible butt. And there's always a butt
<v Speaker 2>in these big discovery stories. As I was reading through
<v Speaker 2>the notes here, there's a section labeled the scientific mystery.
<v Speaker 3>Ah. Yes, the thermal activation Gap.
<v Speaker 2>It sounds like the title of a Robert Ludlam thriller,
<v Speaker 2>The thermal activation Gap.
<v Speaker 3>It is a thriller, at least for the condensed matter theorists,
<v Speaker 3>because what they found when they dug deeple into the
<v Speaker 3>data makes absolutely no sense. Based on the old rules
<v Speaker 3>of the game.
<v Speaker 2>So set the scene for us. They have the device,
<v Speaker 2>it's working, zero resistance. The champagne has been popped, and
<v Speaker 2>then they decide to just mess with it.
<v Speaker 3>Scientists always mess with it, that's the job. They asked
<v Speaker 3>a very logical question. Okay, this state is perfect at
<v Speaker 3>zero magnetic field, but what happens if we add a
<v Speaker 3>small magnetic field?
<v Speaker 2>Now, based on everything we just talked about with the
<v Speaker 2>original quantum Hall effect, the magnet is the friend. The
<v Speaker 2>magnet is what creates the state in the first place,
<v Speaker 2>So adding more magnet should make the state even stronger, right,
<v Speaker 2>more robust.
<v Speaker 3>That is exactly the intuition everyone had in a standard
<v Speaker 3>fractional quantum Hall system in say alium arsenide, if you
<v Speaker 3>increase the magnetic field, you increase the gap.
<v Speaker 2>Okay, define gap for us again quickly. Yeah, the thermal
<v Speaker 2>activation gap.
<v Speaker 1>Right.
<v Speaker 3>Think of the gap as the width of a moat
<v Speaker 3>protecting a castle. Inside the castle, all the electrons are
<v Speaker 3>safe and sound in their perfect fractional state. Outside the
<v Speaker 3>moat is chaos. To destroy the state, an enemy like
<v Speaker 3>thermal energy has to kick an electron all the way
<v Speaker 3>across the moat.
<v Speaker 2>So a wider moat, a larger energy gap is better. Yeah,
<v Speaker 2>it means the castle is more secure, the state is
<v Speaker 2>more stable.
<v Speaker 3>Precisely, so, they turn on the magnetic field, expecting the
<v Speaker 3>moat to get wider. It got narrower.
<v Speaker 2>It shrank. The magnet made the state weak.
<v Speaker 3>It collapsed. As they slowly cranked up the magnetic field
<v Speaker 3>from zero, the thermal activation gap dropped rapidly. It became
<v Speaker 3>easier to destroy the state. The magnet, their old friend
<v Speaker 3>was actively attacking the stability of this new state.
<v Speaker 2>That is completely backwards from how it's supposed to work.
<v Speaker 3>It is profoundly counterintuitive. There's a line in the paper
<v Speaker 3>where you and the team right to our surprise, which
<v Speaker 3>is you know, scientists code for we were completely baffled.
<v Speaker 3>And this makes no sense. The gap decreased quickly and
<v Speaker 3>then eventually plateaued at a lower value.
<v Speaker 2>So what is the theory. Why if the magnet is
<v Speaker 2>supposed to help, why is it hurting. Here?
<v Speaker 3>The leading hypothesis, and it is just a hypothesis at
<v Speaker 3>this point, involves a kind of civil war inside the
<v Speaker 3>quantum state itself.
<v Speaker 2>A civil war, yes.
<v Speaker 3>A competition between different quantum properties of the electrons. In
<v Speaker 3>these TMD materials, electrons don't just have charge and spin
<v Speaker 3>up or down. They also have another property called valley valley.
<v Speaker 2>What's that.
<v Speaker 3>In the momentum energy landscape of the crystal, there are
<v Speaker 3>two distinct lowest energy valleys where electrons can live. They're
<v Speaker 3>called the K and K prime valleys. You can think
<v Speaker 3>of it as another quantum number, like another flavor of spin.
<v Speaker 2>So electrons have spin and they have flavor basically. Yes.
<v Speaker 3>Now, the magnetic field is very good at one thing.
<v Speaker 3>It loves to align spin. A magnetic field wants all
<v Speaker 3>the electrons spins to point in one direction. That's the Zeman effect.
<v Speaker 2>Okay, that makes sense. It's aligning all the little internal magnets, right.
<v Speaker 3>But the theorists think that the stability of the fractional
<v Speaker 3>state in this specific twisted material might depend on a
<v Speaker 3>very particular arrangement of the valleys. It might want the
<v Speaker 3>valleys to be polarized or mixed in a certain way
<v Speaker 3>that has nothing to do with spin.
<v Speaker 2>And the magnet comes in and messes up that valley
<v Speaker 2>arrangement exactly.
<v Speaker 3>The magnet storms in and says, attention, everyone, aligned by
<v Speaker 3>your spin. But the delicate fractional state says no, wait,
<v Speaker 3>we need to be aligned by our valley to maintain
<v Speaker 3>this collective dance. The two orders are competing. The magnet
<v Speaker 3>is forcing the system into a spin configuration that is
<v Speaker 3>not the optimal configuration for the valley based fractional state.
<v Speaker 2>So the mote shrinks because the very foundation of the
<v Speaker 2>castle is shaking from this internal conflict.
<v Speaker 3>That is a brilliant way to put it. The shrinking
<v Speaker 3>gap is the experimental evidence that the topology of this
<v Speaker 3>new state is much more complex and richer than the
<v Speaker 3>simple quantum hollow effect. It's born from this weird interplay
<v Speaker 3>of spin, valley and the more physics.
<v Speaker 2>So does this new mystery Does it ruin the discovery
<v Speaker 2>at all?
<v Speaker 3>Not at all. In many ways, it makes it even
<v Speaker 3>more exciting. It's a giant sign post that says new
<v Speaker 3>physics here. It means we don't fully understand what we've created,
<v Speaker 3>and that's the best place to be in science.
<v Speaker 2>It's not a bug, it's a feature.
<v Speaker 3>It's a new discovery that's come along for the ride.
<v Speaker 3>It gives us a new knob to turn and a
<v Speaker 3>new puzzle to solve.
<v Speaker 2>This brings us to the final section the future outlook,
<v Speaker 2>Shaodong Shoe seems incredibly optimistic. In the paper's conclusion, he
<v Speaker 2>has this great quote, the quantum hall community has made
<v Speaker 2>repeated breakthroughs by improving sample quality over the last forty years.
<v Speaker 3>That's the clean lens philosophy of science.
<v Speaker 2>Explain what you mean by that.
<v Speaker 3>Think of early astronomers looking at the sky through a dirty,
<v Speaker 3>low quality telescope. You see a faint, fuzzy blur. You
<v Speaker 3>might think that blur is a single star. But then
<v Speaker 3>you spend years grinding a better lens, making it cleaner
<v Speaker 3>and more perfect. Okay, you look through the new clean
<v Speaker 3>lens and you realize that blaur wasn't a star at all.
<v Speaker 3>It was an entire galaxy, or it was binary star system.
<v Speaker 3>The dirt in your instrument was hiding the true, more
<v Speaker 3>complex reality.
<v Speaker 2>The dirt hides the details.
<v Speaker 3>For forty years, the atomic scale, dirt and disorder in
<v Speaker 3>our materials has been hiding the true bizarre nature of
<v Speaker 3>interacting electrons. As we clean the lens with these incredible
<v Speaker 3>techniques like horizontal flux growth and low disorder fabrication, we
<v Speaker 3>aren't just making things more efficient, We are revealing new
<v Speaker 3>laws of physics that were hidden in the noise.
<v Speaker 2>Zoo follows that up by saying, we hope that the
<v Speaker 2>progress on this new platform will be even faster.
<v Speaker 3>And I think he's right to be optimistic, because now
<v Speaker 3>we have a recipe. It's not a mystery anymore. We
<v Speaker 3>know the key ingredients. High purity MOTI two two, the
<v Speaker 3>flux growth method, the low disorder twist. Any lab in
<v Speaker 3>the world with the right equipment can now start making
<v Speaker 3>these high quality devices and exploring.
<v Speaker 2>So the floodgates are about to open.
<v Speaker 3>People can try different twist angles, different layer fominations, different
<v Speaker 3>TMD materials. It really feels like we are standing on
<v Speaker 3>the beach of a new continent and we've just figured
<v Speaker 3>out how to build the boats.
<v Speaker 2>I want to circle all the way back to where
<v Speaker 2>we started this conversation. That hot phone in your pocket,
<v Speaker 2>that roaring data center.
<v Speaker 3>The radiator world we live in.
<v Speaker 2>It really feels like we are living in the steam
<v Speaker 2>age of computing. It's loud, it's hot, it's incredibly inefficient.
<v Speaker 3>We absolutely are. We are brute forcing electrons through solid
<v Speaker 3>rock and just dealing with the heat as a waste product.
<v Speaker 2>In this research, this dissipationless fractional churn insulator. This feels
<v Speaker 2>like the first real glimpse of the solid state silent electric.
<v Speaker 3>Future it is. It's a future where electrical current flows
<v Speaker 3>like a superfluid, where heat becomes an engineering choice, not
<v Speaker 3>an inevitable byproduct, where quantum information isn't stored on a material,
<v Speaker 3>but is braided into the very fabric of the material itself.
<v Speaker 2>It's just mind blowing stuff, and the fact that this
<v Speaker 2>is happening now in twenty twenty six makes me incredibly
<v Speaker 2>excited to see what the landscape looks like by twenty thirty.
<v Speaker 3>The pace of discovery here is just breathtaking.
<v Speaker 2>I think I want to leave our listener with one
<v Speaker 2>final thought, tom all over. We often look for the
<v Speaker 2>next big thing in a new app or a new
<v Speaker 2>gadget design, but sometimes the biggest revolutions are completely invisible.
<v Speaker 2>They're happening at the atomic scale inside a tiny flake
<v Speaker 2>of crystal that has been twisted just right.
<v Speaker 3>The twist is the key.
<v Speaker 2>Thank you so much for walking us through this. I
<v Speaker 2>feel like I finally actually understand what a churn insulator is.
<v Speaker 3>It was my absolute pleasure. This is the kind of
<v Speaker 3>stuff that makes being a physicist fun and.
<v Speaker 2>To everyone listening, thank you for being part of this exploration.
<v Speaker 2>Keep your devices cool, stay curious, and we will see
<v Speaker 2>you in the next deep dive.