Latest / The Quark Side - Quantum Physics Podcast / Scientists Discover a New Form of the Hall Effect That Defies a Century-Old Assumption

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Scientists Discover a New Form of the Hall Effect That Defies a Century-Old Assumption · The Quark Side - Quantum Physics Podcast

• 0:01
  Speaker 1: Welcome to the QuarkSide Quantum Physics Podcast, an exploration of
• 0:05
  Speaker 1: the fundamental structure of reality, where quantum laws govern matter, energy,
• 0:11
  Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
• 0:16
  Speaker 1: and understanding begins at the smallest scales.
• 0:27
  Speaker 2: If you've ever... typed on a really high-end computer keyboard,
• 0:32
  Speaker 2: or relied on your car's anti-lock brakes during a bad rainstorm,
• 0:36
  Speaker 2: you have actually utilized a fundamental rule of physics that
• 0:39
  Speaker 2: was written all the way back in 1879.
• 0:41
  Speaker 3: Yeah, it's pretty wild to think about.
• 0:43
  Speaker 2: Right, and for nearly 140 years, scientists thought they knew
• 0:47
  Speaker 2: exactly how this specific rule worked. It was completely settled science.
• 0:52
  Speaker 3: Or so they thought.
• 0:53
  Speaker 2: Exactly, so they thought. Because a team of physicists just
• 0:56
  Speaker 2: recently proved them wrong simply by slicing a material down
• 1:00
  Speaker 2: to a few atoms thick and watching electricity do something
• 1:03
  Speaker 2: that was supposed to be completely impossible.
• 1:06
  Speaker 3: It really is the kind of breakthrough that forces you
• 1:08
  Speaker 3: to rewrite the textbooks. I mean, we are looking at
• 1:10
  Speaker 3: a foundational pillar of condensed matter physics that has essentially
• 1:15
  Speaker 3: been flipped entirely on its head, all because of these
• 1:18
  Speaker 3: recent advancements in nanotechnology.
• 1:20
  Speaker 2: I love when settled science gets unsettled.
• 1:22
  Speaker 3: Oh, me too.
• 1:23
  Speaker 2: We are talking about a groundbreaking discovery by scientists at
• 1:27
  Speaker 2: Carnegie Mellon University that fundamentally changes our understanding of something
• 1:30
  Speaker 2: called the Hall effect. Now, if you aren't a physics major,
• 1:34
  Speaker 2: do not panic.
• 1:35
  Speaker 3: No need to panic at all.
• 1:36
  Speaker 2: We are going to break all of this down for you.
• 1:39
  Speaker 2: The mission today is to explore exactly what this century-old
• 1:42
  Speaker 2: rule is, how researchers managed to literally break it using
• 1:47
  Speaker 2: ultrathin materials, And, you know, why this invisible nanoscale breakthrough
• 1:53
  Speaker 2: could revolutionize the technology you interact with every single day.
• 1:56
  Speaker 3: The historical context here really is what makes this so monumental.
• 2:00
  Speaker 3: When a rule has been the absolute standard tool for
• 2:03
  Speaker 3: understanding how electronic materials respond to magnetic fields for more
• 2:06
  Speaker 3: than a century, well, discovering an entirely new dimension to
• 2:10
  Speaker 3: it isn't just an academic curiosity.
• 2:13
  Speaker 2: Right.
• 2:13
  Speaker 3: It genuinely shifts the foundation of material science.
• 2:16
  Speaker 2: Okay, let's unpack this, because to fully appreciate how big
• 2:19
  Speaker 2: of a deal it is that they broke the rule,
• 2:20
  Speaker 2: we have to actually understand the rule itself. So this
• 2:23
  Speaker 2: takes us back to 1879.
• 2:24
  Speaker 3: A very long time ago.
• 2:26
  Speaker 2: Yeah, a physicist named Edwin Hall makes this discovery that
• 2:29
  Speaker 2: became known as the Hall effect.
• 2:31
  Speaker 3: And keep in mind, in 1879, our understanding of electricity
• 2:35
  Speaker 3: was still in its relative infancy.
• 2:37
  Speaker 2: I mean, they didn't even know what an electron was yet, right?
• 2:39
  Speaker 3: Exactly. The electron itself wouldn't even be officially discovered for
• 2:43
  Speaker 3: another 18 years. But Edwin Hall was experimenting with how
• 2:47
  Speaker 3: electricity and magnetism interact, and he established a really basic,
• 2:52
  Speaker 3: classic rule.
• 2:53
  Speaker 2: Which was?
• 2:54
  Speaker 3: Well, if you have an electric current flowing through a
• 2:56
  Speaker 3: conductive material, and you apply a magnetic field that is
• 3:00
  Speaker 3: exactly perpendicular to that material, meaning the magnetic field cuts
• 3:04
  Speaker 3: straight down through the electrical flow at a flat 90-degree angle,
• 3:08
  Speaker 3: it actually deflects those moving electric charges.
• 3:11
  Speaker 2: It pushes them. Right.
• 3:12
  Speaker 3: It physically pushes them to the side of the material.
• 3:15
  Speaker 2: I always find this a lot easier to picture with
• 3:16
  Speaker 2: a visual. So imagine a huge crowd of people running
• 3:19
  Speaker 2: straight down a long, narrow hallway. The people, they represent
• 3:23
  Speaker 2: the electric current, just charges moving along through a wire.
• 3:26
  Speaker 3: I like this.
• 3:27
  Speaker 2: Now imagine a massive, powerful crosswind suddenly blows through the
• 3:31
  Speaker 2: hallway from an open side door. That crosswind is our
• 3:34
  Speaker 2: perpendicular magnetic field. What happens to the crowd?
• 3:38
  Speaker 3: They can't keep running in a straight line.
• 3:40
  Speaker 2: Exactly. They get blown totally off course and end up, like,
• 3:43
  Speaker 2: piling up against one wall of the hallway.
• 3:46
  Speaker 3: The hallway analogy works really well here, but let's look
• 3:48
  Speaker 3: at the consequence of that pileup. When those electrical charges
• 3:52
  Speaker 3: get pushed against the wall of the material by that
• 3:54
  Speaker 3: perpendicular magnetic field, you suddenly have a high concentration of
• 3:58
  Speaker 3: charge on one side of the material.
• 4:00
  Speaker 2: And a low concentration on the other side.
• 4:02
  Speaker 3: Precisely. And that imbalance creates a measurable voltage across the material.
• 4:07
  Speaker 3: That specific voltage, the actual size of that tileup on
• 4:11
  Speaker 3: the side of the hallway, That is why Edwin Hall's
• 4:13
  Speaker 3: discovery became the gold standard.
• 4:15
  Speaker 2: So by measuring the pileup, scientists can sort of work
• 4:18
  Speaker 2: backward to understand what the crowd is made of.
• 4:21
  Speaker 3: Exactly. They can determine if the electric current is being
• 4:24
  Speaker 3: carried by negative charges or positive charges. They can figure
• 4:28
  Speaker 3: out the density of the charges. And they can measure
• 4:32
  Speaker 3: how easily they flow through the specific atomic structure of
• 4:36
  Speaker 3: that material.
• 4:36
  Speaker 4: Wow.
• 4:37
  Speaker 3: It essentially became the ultimate diagnostic tool To profile a
• 4:42
  Speaker 3: material's electronic properties.
• 4:43
  Speaker 2: And this isn't just some neat party trick for 19th
• 4:46
  Speaker 2: century physicists either. The Hall effect is the basis for
• 4:49
  Speaker 2: the sensing technologies we rely on today. Like take the
• 4:53
  Speaker 2: anti-lock brakes in your car.
• 4:54
  Speaker 3: A very practical example.
• 4:56
  Speaker 2: Inside the wheel hub, there is a little gear with
• 4:58
  Speaker 2: magnetic teeth spinning around. Next to it is a Hall
• 5:02
  Speaker 2: effect sensor with a constant current running through it. Every
• 5:05
  Speaker 2: time a magnetic tooth passes by the sensor, it creates
• 5:08
  Speaker 2: that perpendicular crosswind.
• 5:09
  Speaker 3: The electrons pile up on the side.
• 5:11
  Speaker 2: Right, and the sensor registers a voltage spike. The card's
• 5:14
  Speaker 2: computer counts those spikes to know exactly how fast the
• 5:17
  Speaker 2: wheel is spinning.
• 5:18
  Speaker 3: Or consider those high-end computer keyboards we mentioned. Underneath the keys,
• 5:22
  Speaker 3: instead of a standard physical mechanical switch that eventually wears
• 5:26
  Speaker 3: out over time, there's a magnet and a Hall effect sensor.
• 5:30
  Speaker 2: Oh, that makes sense.
• 5:31
  Speaker 3: Yeah, as you press the key down, the magnet gets
• 5:33
  Speaker 3: closer to the sensor... The perpendicular magnetic field gets stronger,
• 5:36
  Speaker 3: the voltage changes, and the computer registers the keystroke with
• 5:39
  Speaker 3: just incredible precision.
• 5:41
  Speaker 2: It is everywhere. But the catch, the absolute golden rule
• 5:45
  Speaker 2: of this technology for 140 years, was the angle.
• 5:49
  Speaker 3: The rule was completely rigid. The magnetic field had to
• 5:52
  Speaker 3: be perpendicular. It had to be that crosswind hitting the
• 5:55
  Speaker 3: flow of electricity at a 90 degree angle.
• 5:58
  Speaker 2: No exceptions.
• 5:59
  Speaker 3: None.
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  Speaker 4: None.
• 6:00
  Speaker 3: If the wind blows parallel to the hallway, meaning the
• 6:03
  Speaker 3: magnetic field is flat along the same plane as the material,
• 6:05
  Speaker 3: running in the exact same direction as the current, the
• 6:08
  Speaker 3: math said nothing should happen.
• 6:10
  Speaker 2: So no deflection.
• 6:11
  Speaker 3: No deflection, no pileup, no voltage whatsoever.
• 6:14
  Speaker 2: Because, I mean, a wind blowing at your back shouldn't
• 6:16
  Speaker 2: push you into a wall.
• 6:18
  Speaker 3: That was exactly the prevailing logic.
• 6:19
  Speaker 2: But a team of researchers in Carnegie Mellon's Department of Physics,
• 6:23
  Speaker 2: specifically working in the lab for investigating quantum materials, interfaces,
• 6:27
  Speaker 2: and devices, which has the incredible acronym LQID, they just
• 6:32
  Speaker 2: proved that logic wrong.
• 6:33
  Speaker 3: They certainly did.
• 6:34
  Speaker 2: Led by Simranjeet Singh, they discovered the in-plane anomalous Hall effect.
• 6:39
  Speaker 2: They proved you actually can get a response when the
• 6:42
  Speaker 2: magnetic field is applied flat along the plane of the material.
• 6:46
  Speaker 3: They demonstrated that you don't actually need the perpendicular crosswind
• 6:49
  Speaker 3: at all. The magnetic wind can be blowing straight down
• 6:52
  Speaker 3: the hallway alongside the runners, and somehow... the runners still
• 6:55
  Speaker 3: violently swerve and pile up on the wall.
• 6:58
  Speaker 2: Wait, okay, going back to my hallway analogy for a second,
• 7:00
  Speaker 2: I have to push back on the physics of this.
• 7:02
  Speaker 3: Go for it.
• 7:03
  Speaker 2: If the wind is blowing parallel, like straight down the
• 7:05
  Speaker 2: hallway with the runners, wouldn't it just speed them up
• 7:08
  Speaker 2: or slow them down? How on earth does a force
• 7:11
  Speaker 2: pushing you straight ahead cause you to veer sideways into
• 7:14
  Speaker 2: a wall? That doesn't make any mechanical sense.
• 7:17
  Speaker 3: What's fascinating here is that you are having the exact
• 7:19
  Speaker 3: same reaction physicists had for decades. Mechanically, In a standard environment,
• 7:26
  Speaker 3: it simply doesn't make sense. And this raises an important question.
• 7:29
  Speaker 2: Which is?
• 7:30
  Speaker 3: What kind of environment would force that sideways movement? And
• 7:34
  Speaker 3: the answer comes down to crystal symmetry.
• 7:36
  Speaker 2: Crystal symmetry, meaning how the actual atoms are arranged in
• 7:40
  Speaker 2: the metal.
• 7:40
  Speaker 3: Yes, exactly. Think of a standard crystal lattice like a
• 7:44
  Speaker 3: perfectly symmetrical grid of city streets. When an electron travels
• 7:48
  Speaker 3: through that grid, the forces acting on it are completely balanced.
• 7:52
  Speaker 2: Okay, so it goes straight.
• 7:53
  Speaker 1: Right.
• 7:54
  Speaker 3: If a magnetic field pushes it slightly left, the symmetrical geometry,
• 7:58
  Speaker 3: the atoms on the right, pulls it back into alignment.
• 8:00
  Speaker 3: Everything just cancels out. But theorists proposed that if you
• 8:04
  Speaker 3: could somehow find a material with a highly asymmetrical, almost
• 8:07
  Speaker 3: ugly crystal structure where the grid is warped uneven, the
• 8:11
  Speaker 3: internal forces wouldn't cancel out. Oh, wow.
• 8:13
  Speaker 2: So the environment itself is what causes the swerve. The
• 8:16
  Speaker 2: theorists basically said, hey, this parallel wind could push people
• 8:20
  Speaker 2: into the wall and But only if the floor of
• 8:22
  Speaker 2: the hallway is tilted at a bizarre angle and covered
• 8:25
  Speaker 2: in speed bumps?
• 8:25
  Speaker 3: That captures the idea perfectly. The theory existed, but for
• 8:29
  Speaker 3: a very long time it was a profound materials problem.
• 8:33
  Speaker 2: It's hard to make that tilted floor.
• 8:35
  Speaker 3: It is incredibly difficult to find a material that has
• 8:37
  Speaker 3: this highly specific, asymmetrical structural arrangement that also happens to
• 8:42
  Speaker 3: be magnetic. The natural world simply didn't provide a crystal
• 8:46
  Speaker 3: that fit the math.
• 8:47
  Speaker 2: So if this perfect material doesn't exist in nature because
• 8:50
  Speaker 2: of how crystals normally form, I'm guessing they couldn't just
• 8:53
  Speaker 2: like dig this out of the ground. They had to
• 8:55
  Speaker 2: invent a completely new material.
• 8:57
  Speaker 3: They had to build it, quite literally atom by atomic layer.
• 9:01
  Speaker 3: And this is where Jodi Katok's expertise comes into the picture.
• 9:04
  Speaker 2: She works at CMU too, right?
• 9:05
  Speaker 1: Yes.
• 9:06
  Speaker 3: She's an expert in fabricating devices from two-dimensional quantum materials.
• 9:11
  Speaker 3: Her team works with a level of precision that involves
• 9:13
  Speaker 3: peeling materials down until they are unfathomably thin.
• 9:17
  Speaker 2: To build this tilted hallway, what kind of foundation did
• 9:20
  Speaker 2: they even use for that? Are we talking about a
• 9:21
  Speaker 2: new kind of metal here?
• 9:22
  Speaker 3: They started with a compound called tantalum iridium telluride, or
• 9:27
  Speaker 3: Tertae-4 for short.
• 9:29
  Speaker 2: Tertae. I am assuming that is not something you just
• 9:31
  Speaker 2: pick up at the hardware store.
• 9:32
  Speaker 3: Far from it. Tertae-4 is the secret ingredient because it
• 9:36
  Speaker 3: inherently possesses that rare asymmetrical crystalline structure we just talked about.
• 9:41
  Speaker 3: If atoms naturally arrange themselves in a way that breaks
• 9:44
  Speaker 3: the symmetrical grid.
• 9:45
  Speaker 2: Okay, so it gives us the tilted floor and the
• 9:47
  Speaker 2: speed bumps.
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  Speaker 3: It does. But there is a massive catch.
• 9:52
  Speaker 2: Let me guess. It has the right structure, but it
• 9:55
  Speaker 2: isn't magnetic.
• 9:56
  Speaker 3: You hit the nail right on the head. On its own,
• 9:58
  Speaker 3: it is completely non-magnetic. so it can't actually interact with
• 10:01
  Speaker 3: the electric current in the way the Hall effect requires.
• 10:05
  Speaker 2: So they have the structural environment, but they are missing
• 10:07
  Speaker 2: the engine to drive the phenomenon. How do you make
• 10:11
  Speaker 2: a non-magnetic crystal magnetic without completely destroying its delicate asymmetrical structure?
• 10:18
  Speaker 3: You rely on extremely close quarters. Katok's team, working alongside
• 10:22
  Speaker 3: researchers Ai-Huswan Cao and Ravi Kumar, took this Tarte 4
• 10:27
  Speaker 3: and thinned it down to just a few atomic layers.
• 10:29
  Speaker 2: Almost invisible.
• 10:30
  Speaker 3: Essentially, yes. Then they brought in a second material, a
• 10:34
  Speaker 3: compound called CR2G2ET6. We'll just call it CGT to keep
• 10:39
  Speaker 3: things simple. And CGT is strongly magnetic.
• 10:42
  Speaker 2: Here's where it gets really interesting because they are dealing
• 10:44
  Speaker 2: with layers so thin they're practically two-dimensional. If you stack
• 10:49
  Speaker 2: a magnetic layer on top of a non-magnetic layer at
• 10:51
  Speaker 2: the atomic scale, does it cause a proximity effect?
• 10:55
  Speaker 3: Proximity effect.
• 10:56
  Speaker 2: Yeah, sort of like if you take a plain, ordinary
• 10:59
  Speaker 2: iron nail and you let it sit right next to
• 11:01
  Speaker 2: a really powerful magnet. After a while, the plain iron
• 11:03
  Speaker 2: nail actually catches the magnetism just by being in close contact, right?
• 11:07
  Speaker 3: The proximity effect is definitely the mechanism, but at the
• 11:10
  Speaker 3: atomic level, it is far more instantaneous and integrated than
• 11:13
  Speaker 3: the iron nail example. Because these two layers, the uniquely
• 11:17
  Speaker 3: asymmetrical tarte four and the magnetic CGT, are atomically thin
• 11:20
  Speaker 3: and pressed together with essentially zero gap. Oh, wow.
• 11:24
  Speaker 2: So they're basically merging. Right.
• 11:26
  Speaker 3: Their proximity causes a profound quantum interaction. The magnetic properties
• 11:32
  Speaker 3: literally leak from the CGT layer directly into the non-magnetic
• 11:37
  Speaker 3: tarte four layer.
• 11:38
  Speaker 2: So the magnetic properties just bleed over into the non-magnetic layer,
• 11:41
  Speaker 2: essentially infecting it with magnetism, while somehow leaving its weird,
• 11:45
  Speaker 2: asymmetrical atomic structure completely intact.
• 11:49
  Speaker 3: That is the true power of what material scientists call
• 11:51
  Speaker 3: atomically precise heterostructures.
• 11:54
  Speaker 2: Atomically precise heterostructures.
• 11:55
  Speaker 3: Yes. By stacking these specific 2D layers, they can imbue
• 11:59
  Speaker 3: a material with magnetic properties on demand, completely customizing its behavior.
• 12:04
  Speaker 3: They basically built an atomic sandwich that the natural universe
• 12:07
  Speaker 3: simply does not produce on its own.
• 12:09
  Speaker 2: Okay, so they build this atomic sandwich, the magnetism leaks
• 12:12
  Speaker 2: into the asymmetrical layer, and suddenly they run a current
• 12:15
  Speaker 2: through it, apply a flat parallel magnetic field, and they
• 12:18
  Speaker 2: observe the electrons swerving. They see the in-plane anomal and
• 12:21
  Speaker 2: Hall effect actually happen.
• 12:23
  Speaker 3: They do.
• 12:24
  Speaker 2: But observing an electron swerving and explaining the invisible forces
• 12:27
  Speaker 2: causing it to swerve are two totally different things. What
• 12:30
  Speaker 2: was actually happening inside that sandwich to cause this?
• 12:33
  Speaker 3: That required entirely new theoretical modeling. A theoretical physicist named
• 12:39
  Speaker 3: Shupayu Chatterjee analyzed the results to identify the exact mechanism
• 12:43
  Speaker 3: at play. And he found that the pairing of these
• 12:45
  Speaker 3: two materials, combined with the leaked magnetism, supercharges something called
• 12:49
  Speaker 3: spin-orbit coupling at the interface where the two materials meet.
• 12:53
  Speaker 2: Okay, spin-orbit coupling. We promised no overwhelming jargon, so we
• 12:56
  Speaker 2: need to understand the basic physics here. How do we
• 12:59
  Speaker 2: visualize this interaction?
• 13:01
  Speaker 3: We need to look at the electron itself. Imagine an
• 13:04
  Speaker 3: electron orbiting the nucleus of an atom, somewhat similar to
• 13:07
  Speaker 3: how the Earth orbits the sun. But just like the Earth,
• 13:10
  Speaker 3: the electron isn't just traveling in a circle, it is
• 13:13
  Speaker 3: also constantly spinning on its own axis.
• 13:15
  Speaker 2: So it has an orbit around the center and its
• 13:18
  Speaker 2: own internal spin.
• 13:19
  Speaker 3: Yes. Now, because an electron holds an electrical charge, the
• 13:22
  Speaker 3: fact that it is spinning means it generates its own
• 13:25
  Speaker 3: tiny microscopic magnetic field.
• 13:27
  Speaker 2: Okay, I follow you.
• 13:28
  Speaker 3: Spin-order coupling is the interaction between the electron's own tiny
• 13:32
  Speaker 3: magnetic field generated by its spin and the larger magnetic
• 13:35
  Speaker 3: environment it is moving through.
• 13:37
  Speaker 2: Ah, I see. So when you squeeze this spinning electron
• 13:40
  Speaker 2: into this highly asymmetrical atomic sandwich and you apply that
• 13:45
  Speaker 2: parallel magnetic wind, the electron's own spin catches the force differently.
• 13:50
  Speaker 3: Exactly.
• 13:50
  Speaker 2: It's like throwing a curveball in baseball. The pitcher throws
• 13:54
  Speaker 2: the ball straight ahead, but because the ball is spinning rapidly,
• 13:57
  Speaker 2: The friction of the air catches the seams unevenly and
• 14:00
  Speaker 2: the ball violently swerves to the side before it reaches
• 14:03
  Speaker 2: home plate.
• 14:04
  Speaker 3: The curve ball is an outstanding way to visualize it.
• 14:07
  Speaker 3: In most standard symmetrical materials, that curve ball effect gets
• 14:11
  Speaker 3: corrected by the perfectly balanced structure of the crystal lattice.
• 14:15
  Speaker 2: The environment fixes it.
• 14:16
  Speaker 3: Right. The ball tries to swerve, but the environment pushes
• 14:19
  Speaker 3: it back to the center. But in this unique Tertia
• 14:23
  Speaker 3: 4 sandwich, the environment is deliberately unbalanced. The magnetism leaped in,
• 14:28
  Speaker 3: the crystal structure is warped, and when the parallel magnetic
• 14:31
  Speaker 3: field hits that spinning electron, the spin-orbit coupling acts exactly
• 14:35
  Speaker 3: like the stones on the baseball.
• 14:36
  Speaker 4: Unbelievable.
• 14:37
  Speaker 3: It forces the electric charge sideways, creating that massive pileup
• 14:41
  Speaker 3: on the wall of the hallway.
• 14:42
  Speaker 2: That is just phenomenal. They engineered a material from scratch
• 14:45
  Speaker 2: to throw an electrical curveball.
• 14:47
  Speaker 3: They really did. Now, just to maintain complete scientific accuracy here,
• 14:51
  Speaker 3: there is one important caveat we should probably mention.
• 14:54
  Speaker 2: There's always a catch. Always. Always.
• 14:55
  Speaker 3: For this specific in-plane curveball to emerge, the magnetic CDT
• 15:00
  Speaker 3: layer has to be in a ferromagnetic state. And currently,
• 15:05
  Speaker 3: with these highly specific materials, that state only occurs at
• 15:09
  Speaker 3: very low temperatures. We're talking well below freezing. So we
• 15:13
  Speaker 3: are not quite at the point where this exact sensor
• 15:15
  Speaker 3: can be dropped into a smartphone sitting in a hot car.
• 15:19
  Speaker 2: So it is a massive breakthrough in fundamental physics, but
• 15:21
  Speaker 2: it is still in the highly controlled, supercooled laboratory phase.
• 15:25
  Speaker 3: For now, yes.
• 15:26
  Speaker 2: But that leads to the ultimate question for you, the listener.
• 15:29
  Speaker 2: We have this amazing atomic scale sandwich. We have electrons
• 15:33
  Speaker 2: throwing curveballs because of leaked magnetism and asymmetrical grids. It
• 15:37
  Speaker 2: literally rewrites a rule of physics from 1879. So what
• 15:39
  Speaker 2: does this all mean? When they eventually get this working
• 15:43
  Speaker 2: at room temperature, what is the practical application?
• 15:46
  Speaker 3: If we connect this to the bigger picture, the most
• 15:49
  Speaker 3: immediate and profound impact will be in a field called
• 15:52
  Speaker 3: vector magnetometry.
• 15:54
  Speaker 2: Vector magnetometry. Let's break that down. I assume this has
• 15:58
  Speaker 2: to do with how sensors measure magnetic fields in three-dimensional space.
• 16:01
  Speaker 3: Exactly. It is the ability to measure both the direction
• 16:04
  Speaker 3: and the strength of a magnetic field. Think about the
• 16:08
  Speaker 3: old rules of the hall effect we talked about. It
• 16:11
  Speaker 3: only worked when a magnetic field was perfectly perpendicular.
• 16:14
  Speaker 2: Right.
• 16:14
  Speaker 3: So if an engineer wanted to measure a magnetic field
• 16:17
  Speaker 3: in two different directions, say the x-axis and the y-axis,
• 16:20
  Speaker 3: they had to build two completely separate sensors and physically
• 16:23
  Speaker 3: mount them perpendicularly to each other.
• 16:25
  Speaker 2: Because one sensor could only read the crosswind from one
• 16:29
  Speaker 2: specific angle, if you want to read a crosswind from
• 16:32
  Speaker 2: the north and a crosswind from the east, you literally
• 16:35
  Speaker 2: need two separate devices facing different ways.
• 16:37
  Speaker 4: Exactly.
• 16:38
  Speaker 3: Exactly. Which means taking up more space on a circuit board,
• 16:41
  Speaker 3: requiring more complex wiring, consuming more power, and generally dealing
• 16:45
  Speaker 3: with more potential points of failure.
• 16:47
  Speaker 2: But now, thanks to the CMU team's discovery, a single
• 16:51
  Speaker 2: ultra-thin device can actually detect magnetic fields along multiple axes
• 16:55
  Speaker 2: at the exact same time.
• 16:56
  Speaker 1: Yes.
• 16:57
  Speaker 2: During their experiments, they observed both the conventional perpendicular Hall
• 17:00
  Speaker 2: signal and the new in-plane parallel signal within the exact
• 17:05
  Speaker 2: same atomic sandwich.
• 17:07
  Speaker 3: They did. the researchers emphasized that this completely broadens the
• 17:11
  Speaker 3: potential applications for magnetic materials. You achieve full multidimensional magnetic
• 17:16
  Speaker 3: sensing with a single flat component.
• 17:18
  Speaker 2: That feels like a massive leap for hardware design, especially when,
• 17:21
  Speaker 2: you know, every tech company on Earth is just obsessed
• 17:24
  Speaker 2: with making things smaller and faster.
• 17:25
  Speaker 3: It is a complete paradigm shift for planar device architectures,
• 17:29
  Speaker 3: meaning microchips and sensors that are built on flat planes.
• 17:32
  Speaker 3: By building sensors that can do double the work at
• 17:34
  Speaker 3: a fraction of the physical space... Our sensing technologies can
• 17:38
  Speaker 3: become drastically smaller, vastly more energy efficient, and just far
• 17:42
  Speaker 3: more capable.
• 17:43
  Speaker 2: What kind of industries are we actually talking about here?
• 17:45
  Speaker 2: Where does vector magnetometry really get used?
• 17:48
  Speaker 3: Well, medical imaging is a prime example.
• 17:50
  Speaker 2: Oh, like MRIs?
• 17:51
  Speaker 3: Exactly. The precision of an MRI machine relies entirely on
• 17:55
  Speaker 3: mapping incredibly complex magnetic fields. If you can make the
• 17:59
  Speaker 3: sensors inside an MRI more sensitive and genuinely multidimensional, you
• 18:04
  Speaker 3: get much higher resolution images. much faster scan times and
• 18:07
  Speaker 3: potentially even smaller, less claustrophobic machines.
• 18:11
  Speaker 2: That would be huge for health care.
• 18:12
  Speaker 3: It really would. It also heavily impacts autonomous transportation. Self-driving
• 18:17
  Speaker 3: cars and delivery drones rely constantly on magnetic sensors for
• 18:21
  Speaker 3: navigation and spatial orientation.
• 18:22
  Speaker 2: So miniaturizing those sensors without losing any capability, in fact,
• 18:26
  Speaker 2: gaining multidimensional capability, That makes the hardware lighter and the
• 18:31
  Speaker 2: data processing way faster.
• 18:33
  Speaker 3: Precisely. It is just.
• 18:34
  Speaker 4: Incredible to think that manipulating things at the atomic level,
• 18:37
  Speaker 4: literally stacking atoms to force magnetism to leak and electrons
• 18:40
  Speaker 4: to throw curveballs, could eventually be the reason an MRI
• 18:43
  Speaker 4: spots a tiny anomaly or your future car navigates a
• 18:47
  Speaker 4: blind intersection more safely.
• 18:49
  Speaker 3: It is. And we are truly just at the starting
• 18:51
  Speaker 3: line of this specific physics application. The research team isn't
• 18:55
  Speaker 3: stopping with Terté.
• 18:56
  Speaker 2: They're looking for more.
• 18:57
  Speaker 3: Absolutely. Now that they have proven the underlying theory is real,
• 19:01
  Speaker 3: they are actively hunting for other 2D material systems that
• 19:04
  Speaker 3: might exhibit this same unconventional in-plane Hall response. And regarding
• 19:10
  Speaker 3: that temperature caveat we discussed earlier, a major focus of
• 19:14
  Speaker 3: their current research is finding material combinations that will exhibit
• 19:17
  Speaker 3: this effect at room temperature.
• 19:19
  Speaker 2: That makes sense.
• 19:20
  Speaker 3: Once they overcome that temperature barrier, the practical engineering applications
• 19:23
  Speaker 3: will rapidly accelerate.
• 19:25
  Speaker 2: We started today by looking at a rule of physics
• 19:28
  Speaker 2: so reliable, so foundational, it has been baked into the
• 19:31
  Speaker 2: fabric of modern technology since the days of horse-drawn carriages.
• 19:35
  Speaker 2: We went from understanding how a magnetic crosswind pushes electricity
• 19:39
  Speaker 2: into a wall to exploring how scientists layered microscopic grids
• 19:43
  Speaker 2: to bend the flow of electricity to their absolute will.
• 19:46
  Speaker 3: It really serves as a brilliant reminder of why fundamental
• 19:49
  Speaker 3: scientific research is so incredibly critical. For over a century,
• 19:52
  Speaker 3: we genuinely thought we had the complete picture of the
• 19:55
  Speaker 3: Hall effect. But by just pushing the boundaries of quantum
• 19:58
  Speaker 3: materials and nanotechnology, we discovered we were only looking at
• 20:01
  Speaker 3: a tiny fraction of the possibilities.
• 20:03
  Speaker 2: It really makes you realize that the rules of science
• 20:05
  Speaker 2: aren't always hard limits, right? Sometimes they are just waiting
• 20:09
  Speaker 2: for better tools. Which leaves a lingering thought for you
• 20:13
  Speaker 2: to mull over today. If 140-year-old unbreakable law of physics
• 20:18
  Speaker 2: just got completely rewritten simply because we finally possessed the
• 20:21
  Speaker 2: technology to build materials atom by atom, what other established
• 20:25
  Speaker 2: scientific boundaries are out there right now just waiting for
• 20:28
  Speaker 2: the right nanoscale sandwich to break them?
• 20:30
  Speaker 3: The deeper we look, the more we realize just how
• 20:33
  Speaker 3: much is still waiting to be discovered.
• 20:35
  Speaker 2: Keep questioning the rules. Catch you next time.