Speaker 1: Welcome to the quart Side. Quantum Physics podcast, an exploration
Speaker 1: of the fundamental structure of reality where quantum laws govern matter, energy,
Speaker 1: and information. Here, uncertainty is a feature, not a flaw,
Speaker 1: and understanding begins at the smallest scales.
Speaker 2: You know, when you think about the microscopic world, it's
Speaker 2: easy to imagine it as this totally chaotic place, just
Speaker 2: a bunch of particles bumping into each other randomly.
Speaker 3: Right, just sort of microscopic soup.
Speaker 2: Yeah, exactly, But there's actually an absolute dictator that governs
Speaker 2: how every single particle behaves. And it's not gravity, and
Speaker 2: it's not some mystical force.
Speaker 3: Oh, it's symmetry, which I mean is a word we
Speaker 3: use all the time in everyday life, but in physics
Speaker 3: it's an entirely different beast.
Speaker 2: Yeah, because when you look at the atomic structure of
Speaker 2: a crystal, symmetry doesn't just describe, you know, how pretty
Speaker 2: or repeating the pattern is. It acts as a strict
Speaker 2: mathematical rule.
Speaker 3: Book, a very rigid rule book. It dictates exactly how
Speaker 3: atoms are arranged and more importantly, how they are allowed to.
Speaker 2: Move, and it specifically hands out absolute do not interact
Speaker 2: orders between certain vibrations, Like, if two vibrations don't share
Speaker 2: the right symmetry, they are categorically forbidden from mixing.
Speaker 3: They cannot mix. It acts as an impenetrable wall. I mean,
Speaker 3: in solid state physics we rely heavily on those exact
Speaker 3: selection rules. They give order to the chaos of billions
Speaker 3: of atoms jiggling around. Right, If symmetry says two quantum
Speaker 3: states can't couple, they don't. We treat that as a
Speaker 3: fundamental constant of the material.
Speaker 2: But today we are looking at a breakthrough that actually
Speaker 2: found a loophole in that exact rule book. We're going
Speaker 2: to explore how a truly bizarre quantum state actively rewrites
Speaker 2: the rigid rules of symmetry in a crystal.
Speaker 3: Yeah, and this isn't just a theoretical curiosity either. It
Speaker 3: can completely changes the way we can manipulate quantum.
Speaker 2: Materials because understanding this loophole is basically a gateway to
Speaker 2: the future of quantum technology. So for you listening, this
Speaker 2: isn't just abstract math. This is the physical foundation for
Speaker 2: the next generation of tech exactly.
Speaker 3: But to understand how a rule that fundamental gives been
Speaker 3: we first have to look at the material where this
Speaker 3: actually happens.
Speaker 2: Right, we have to meet the rule breaker.
Speaker 3: Yes, we're dealing with a specific type of layered crystal,
Speaker 3: a transition metal to calcagenide.
Speaker 2: Which is quite the mouthful, it is.
Speaker 3: Yeah, yeah, But basically inside this material, the ions and
Speaker 3: electrons don't just sit in a standard boring grid. They
Speaker 3: spontaneously rearrange.
Speaker 2: Themselves, okay, rearrange how.
Speaker 3: Into a static wavelike pattern across the crystal lattice. Physicists
Speaker 3: call this a charge density wave.
Speaker 2: A charge density way. So instead of electrons just zipping
Speaker 2: around freely like they do, and say, a normal copper
Speaker 2: wire in your house, right, a normal conductor, right, they're
Speaker 2: bunching up in a periodic pattern like ripples frozen on
Speaker 2: a pond.
Speaker 3: That's actually a really good way to picture it, for
Speaker 3: a frozen ripples. And the specific way they bunch up
Speaker 3: in this material is fascinating. The distortion causes the atoms
Speaker 3: to shift slightly, forming this intricate microscopic tiling of clusters.
Speaker 2: And these clusters have a very specific shape, right they do.
Speaker 3: They look remarkably like the Star of David, like.
Speaker 2: Literally a six pointed star. Geometry just down at the
Speaker 2: atomic level.
Speaker 3: Yes, exactly, And here is where it gets highly exotic.
Speaker 3: These Star of David clusters don't just form symmetrically. They
Speaker 3: have a built in twist and twist, yeah, they can
Speaker 3: lock into one of two distinct orientations, effectively giving the
Speaker 3: crystal a handedness.
Speaker 2: Okay, wait, handedness like left and right hands precisely.
Speaker 3: Yeah, similar to how your left hand in right hand
Speaker 3: or mirror images. But you can't perfectly superimpose them on
Speaker 3: top of each other.
Speaker 2: Right if you put a right handed glove on your
Speaker 2: left hand, it doesn't fit exactly.
Speaker 3: In physics, we call this planar chirality. When a crystal
Speaker 3: establish is this handed pattern, it enters a quantum state
Speaker 3: known as ferro axial order.
Speaker 2: Okay, ferro axial order. Let me make sure I'm visualizing
Speaker 2: this right for you guys listening. I'm picturing a microscopic
Speaker 2: floor tile pattern made of the Star of David shapes.
Speaker 2: But half the floor might be tiled with like left
Speaker 2: handed stars and the other half is tiled with right
Speaker 2: handed stars.
Speaker 3: You're definitely on the right track with that. But the
Speaker 3: challenge with this specific floor pattern is that you can
Speaker 3: actually see it with our standard scientific tool.
Speaker 2: Wait, why not. If it's a physical distortion of the
Speaker 2: electrons and the atoms. Shouldn't we be able to just
Speaker 2: bounce X rays off it or measure its electric field.
Speaker 3: You would think so, but fur axial order is incredibly elusive.
Speaker 3: I mean, think about a standard ferromagnet, like a magnet
Speaker 3: on your fridge. It has a net magnetic moment. All
Speaker 3: the little atomic compass needles point the same way. So
Speaker 3: if you bring a magnetic field near it, it reacts.
Speaker 3: You can measure that reaction easily.
Speaker 2: Yeah, it snaps right onto the fridge.
Speaker 3: Right, But this for axial order doesn't have a net
Speaker 3: electrical dipole, and it doesn't have a net magnetic.
Speaker 2: Moment because of the way the stars are arranged.
Speaker 3: Exactly, because of how the symmetry is broken, those classical
Speaker 3: properties perfectly cancel each other out.
Speaker 2: Oh wow, so it doesn't react to magnets and it
Speaker 2: doesn't react to electric fields at all.
Speaker 3: Nope. Standard optical experiments and conventional probes pass right through it.
Speaker 3: They are completely blind to whether the domains are left
Speaker 3: handed or right handed.
Speaker 2: It's basically a ghost to our standard scientific metal detector.
Speaker 3: That's a great way to put it.
Speaker 2: Yeah, but wait, if it's effectively a ghost, how do
Speaker 2: we even know it's there? Are we just guessing that
Speaker 2: these left and right handed stars exist in the crystal?
Speaker 3: Oh, we're not guessing. We know they're there because the
Speaker 3: pattern isn't a frozen, rigid thing. It's a highly coordinated
Speaker 3: dynamic structure.
Speaker 2: Meaning it moves.
Speaker 3: Yes, those Star of David clusters vibrate, but it's not
Speaker 3: just a random jiggle from heat. They move together in
Speaker 3: a collective synchronized vibration.
Speaker 2: Look at microscopic dance routine sort of, but more like breathing.
Speaker 3: The entire wave pattern periodically expands and contracts in unison.
Speaker 3: It modulates its own strength. Oh. Interesting, and physicists have
Speaker 3: a highly specific term for this collective breathing motion of
Speaker 3: a charged density wave. They call it an amplitude on.
Speaker 2: An amplitude on. Honestly, it sounds like a giant robot
Speaker 2: from an old sci fi movie.
Speaker 3: It does sound like a transformer or something, but.
Speaker 2: It's really just the amplitude of this electron wave pulsing
Speaker 2: in and out right.
Speaker 3: It's the amplitude mode. Now Here's where the central mystery
Speaker 3: of this whole research comes into play. Inside this crystal
Speaker 3: you have this highly specialized amplitude on breathing away, right, Yeah,
Speaker 3: but the crystal also has ordinary vibrations, just the regular
Speaker 3: lattice of atoms jiggling back and forth due to thermal energy.
Speaker 3: Those regular vibrations are called phonons.
Speaker 2: Okay, So you have the amplitude and breathing and the
Speaker 2: phonons jiggling. And because they're in the exact same crystal,
Speaker 2: occupying the exact same physical space, they must be bumping
Speaker 2: into each other, right, I mean they're literally sharing the
Speaker 2: same atoms.
Speaker 3: You would intuitively think so. Remember the absolute dictator we
Speaker 3: talked about earlier. Symmetry, Yeah, the rule book. Yes, the
Speaker 3: amplitude has a very specific symmetry profile and the ordinary
Speaker 3: phonons have a completely different symmetry profile. Mathematically, their wave
Speaker 3: functions are orthogonal.
Speaker 2: Orthogonal, meaning they cross perfectly in a way that creates
Speaker 2: absolutely zero interaction.
Speaker 3: Exactly zero. It is a cosmic soundproof wall. Even though
Speaker 3: they are happening in the exact same material. The rules
Speaker 3: of quantum mechanics dictate that these two distinct vibrations cannot mix, couple,
Speaker 3: or exchange energy at all.
Speaker 2: That is wild. The amplitude and essentially doesn't know the
Speaker 2: ordinary vibrations exist. They're sharing the same dance floor, but
Speaker 2: completely ignoring each other's music.
Speaker 3: That's exactly what's happening, Okay.
Speaker 2: But to even test if that soundproof wall holds up,
Speaker 2: the researchers had to be able to listen to the crystal.
Speaker 2: If electricity and magnetism are off the table, what's left?
Speaker 2: How do you probe an invisible ghost?
Speaker 3: Well you had to get incredibly creative with light. Researchers
Speaker 3: at UT Austin and the Max Planck Institute realized they
Speaker 3: couldn't just use standard linear light. They had to use
Speaker 3: a specialized technique called holicity resolved ram and scattering.
Speaker 2: Okay, holicity resolved, break down the mechanism there, what is
Speaker 2: the light actually doing?
Speaker 3: So they hit the crystal with circularly polarized light. Imagine
Speaker 3: the electric field of the light wave not just waving
Speaker 3: up and down, but physically rotating as it travels through space.
Speaker 2: Like tracing out a corkscrew pattern.
Speaker 3: Yes, exactly like a quarkscrew.
Speaker 2: So the light itself has a handedness. It's twisting either
Speaker 2: clockwise or counterclockwise.
Speaker 3: Precisely it carries angular momentum. Yeah, Now, when this twisting
Speaker 3: light hits a chiral structure, a structure that also has handedness,
Speaker 3: like our star of David flore, the absorption and scattering
Speaker 3: of that light won't be symmetric.
Speaker 2: Ugh, I think I see where this is going. It's
Speaker 2: like trying to drive or right handed screw into a
Speaker 2: piece of wood.
Speaker 3: Okay, I like that right.
Speaker 2: If I spin my screwdriver to the right, matching the
Speaker 2: thread of the screw, it catches, It bites into the wood,
Speaker 2: and I get a really strong reaction. But if I
Speaker 2: take that same right handed screw and I spin my
Speaker 2: screwdriver to the left, it just slips. It doesn't couple
Speaker 2: at all.
Speaker 3: That is a highly accurate mechanical analogy in the crystal.
Speaker 3: When the graduate student running these experiments shoind you paying
Speaker 3: matched the twisting direction of the light to the handedness
Speaker 3: of the feroxial domain, they saw a massive peak in
Speaker 3: the scattered light intensity. Wow. But when they hit that
Speaker 3: same exact spot with light twisting the opposite direction, the
Speaker 3: response was incredibly.
Speaker 2: Weak because it just slipped. The light didn't catch the
Speaker 2: symmetry of the crystal.
Speaker 3: Right. By measuring that difference, the intensity imbalance between the
Speaker 3: left handed and right handed light responses. They could finally
Speaker 3: map out the invisible They could clearly see the microscopic
Speaker 3: handedness of the crystal.
Speaker 2: That is such an elegant solution. You bypass the fact
Speaker 2: that it ignores magnets by literally just matching its physical
Speaker 2: twist with like op tweezer.
Speaker 3: It's brilliant experimental physics.
Speaker 2: Okay, so now they can finally see the ghosts. They
Speaker 2: map out the left and right handed domains. Where does
Speaker 2: the broken roll book come in? Where does symmetry fail?
Speaker 3: Well? Once they could see the pattern, they wanted to
Speaker 3: see how it behaved under different conditions, So they started
Speaker 3: carefully tuning the temperature of the crystal.
Speaker 2: Why temperature does heating it up just make everything vibrate faster?
Speaker 3: Actually, in this specific case, it does something totally counterintuitive.
Speaker 3: As you heat this material up, you bring it closer
Speaker 3: to the temperature where the charge density wave phase completely melts.
Speaker 2: Away, like ice turning to water.
Speaker 3: Kind of yeah. And as it gets closer to melting,
Speaker 3: the restoring force of the wave weakens. Because the force
Speaker 3: is weaker, the frequency of the amplitudin's breathing actually slows down.
Speaker 3: Its energy drops.
Speaker 2: Oh, that is fascinating. So by turning a temperature dial
Speaker 2: on the outside of the sample, you are actively tuning
Speaker 2: the internal frequency of this specific quantum dance routine. You're
Speaker 2: sweeping it through different energy levels.
Speaker 3: Yes, you are tuning the amplitude on. Now, remember those
Speaker 3: ordinary lattice vibrations, the phonons.
Speaker 2: The ones that the amplitude on is strictly forbidden from
Speaker 2: interacting with.
Speaker 3: Right, Well, their frequencies stay relatively constant as the temperature changes.
Speaker 2: Wait, so if the normal vibrations are sitting still at
Speaker 2: let's say fifty terror hurts, and you are sweeping the
Speaker 2: amplitude ons frequency down from one hundred terror hurts, that's
Speaker 2: going to cross. Eventually, their frequencies are going to cross.
Speaker 3: Perfectly they are, And that is exactly where Francesco Barentani
Speaker 3: and the rest of the research team made their massive observation.
Speaker 3: As they tune the temperature, they monitor that specific light
Speaker 3: intensity imbalance we talked about.
Speaker 2: Earlier, the screw catching or slipping.
Speaker 3: Exactly. They found that the chiral signal the imbalance spike
Speaker 3: to its absolute maximum precisely when the energy of the
Speaker 3: amplitude on perfectly matched the energy of one of those
Speaker 3: ordinary phonons.
Speaker 2: Let's pause right there, because this feels like the absolute
Speaker 2: core of the breakthrough symmetry says they cannot interact, But
Speaker 2: you're telling me that when their frequencies match perfectly, they do.
Speaker 3: They do more than interact, They profoundly influence one another.
Speaker 3: Theorist emil Vinas Bostrom describes what happens as a resonant bridge.
Speaker 2: A resonant bridge.
Speaker 3: Under normal conditions, those two vibrational modes are locked in
Speaker 3: entirely separate, mathematically orthogonal rooms. But when you tune their
Speaker 3: energies to align perfectly, the rules of symmetry become dynamically.
Speaker 2: Loosened, dynamically loosen. I'm trying to picture the mechanics of that.
Speaker 2: Does a symmetry just turn off like a light switch.
Speaker 3: It doesn't turn off permanently, but at that exact resonant frequency,
Speaker 3: the wave functions of the two modes are allowed to mix.
Speaker 3: The amplitude essentially acts as a bridge, suddenly linking the
Speaker 3: lower energy atomic motions with the higher energy electronic state
Speaker 3: of the crystal.
Speaker 2: So the soundproof wall gets a temporary window.
Speaker 3: Yes, a window suddenly opens up.
Speaker 2: It's like finding a hidden terms of service agreement in
Speaker 2: the laws of physics, like symmetry applies strictly at all
Speaker 2: times unless internal vibrations hit this exact resonant frequency.
Speaker 3: That's exactly it.
Speaker 2: And then the two locked rooms suddenly share a smuggler's tunnel,
Speaker 2: passing quantum information back and forth.
Speaker 3: It's a fundamental shift in how we view selection rules. Yeah,
Speaker 3: the researchers didn't just observe this anomaly. They built a
Speaker 3: comprehensive microscopic theory to explain the exact mechanics of how
Speaker 3: these electronic fluctuations actively coupled to crystal vibrations that symmetry
Speaker 3: usually keeps completely isolated.
Speaker 2: That is a massive win for theoretical physics. But you
Speaker 2: know me, I always want to know what this means. Practically,
Speaker 2: finding a loophole on a chalkboard is great, but exploiting
Speaker 2: it in the real world is where technology actually changes, and.
Speaker 3: That transition to the real world is where a group
Speaker 3: at the University of Hamburg comes into the picture. Michael
Speaker 3: Rubhausen's group took these findings, confirmed the robustness of the
Speaker 3: model and highlighted a point that completely transforms the utility
Speaker 3: of this discovery.
Speaker 2: Okay, what's the point this entire.
Speaker 3: Effect, this resonant bridging, this loosening of symmetry, It operates
Speaker 3: robustly at room temperature.
Speaker 2: Wait, hold on, you have to explain how that is possible.
Speaker 2: Every time we discuss exotic quantum states or delicate wave
Speaker 2: functions mixing, we are talking about massive, multi million dollar
Speaker 2: lab freezers chilling things down to near absolute zero.
Speaker 3: Right usually, how.
Speaker 2: On earth is this surviving the chaotic thermal noise of
Speaker 2: a room temperature environment. Shouldn't the ambient heat just violently
Speaker 2: scramble the pattern?
Speaker 3: And most systems, yes, absolutely, Thermal fun ons cause rapid decoherence.
Speaker 3: The heat destroys the delicate quantum states. But the coupling
Speaker 3: here driven by this resonant bridging is incredibly strong. And
Speaker 3: more importantly, it occurs on ultra fast time scales. Oh,
Speaker 3: I see the interaction outpaces the thermal noise.
Speaker 2: So it happens so fast the heat literally doesn't have
Speaker 2: time to ruin it exactly.
Speaker 3: This phenomenon has been termed resonant chiral dressing.
Speaker 2: Chiral dressing. Okay, I want to make sure I understand
Speaker 2: dressing in a quantum context. We aren't talking about putting
Speaker 2: a tiny little coat on an atom.
Speaker 3: Right, not quite a coat. In quantum mechanics, dressing refers
Speaker 3: to how a material's fundamental properties are altered when it
Speaker 3: strongly couples with a photon field.
Speaker 2: A photon field so light yes.
Speaker 3: In this case an ultrafast laser pulse. The light doesn't
Speaker 3: just bounce off material, It temporarily merges with the material's identity,
Speaker 3: creating a hybridized state. The crystal is dressed by the
Speaker 3: light field.
Speaker 2: So by using the right twist of light at the
Speaker 2: exact right resonant frequency, you are temporarily dressing the material,
Speaker 2: which bridges the symmetry gap, allowing these completely isolated quantum
Speaker 2: states to talk to each other. Yes, and you can
Speaker 2: do all of this sitting on a normal desk in
Speaker 2: a normal room temperature lab.
Speaker 3: You're starting to see the true power of this. It
Speaker 3: provides a highly practical new route to probe and actively
Speaker 3: control ferro axial quantum states without the crippling overhead of
Speaker 3: cryogenic cooling.
Speaker 2: That completely bypasses one of the biggest roadblocks in quantum
Speaker 2: engineering today.
Speaker 3: It really does. Scientists can now use ultrafast laser pulses
Speaker 3: precisely tuned to these resonant energies to selectively turn on
Speaker 3: these forbidden interactions. That's amating. You can dynamically switch a
Speaker 3: quantum connection on and off just by hitting the crystal
Speaker 3: with the right burst of light.
Speaker 2: It's essentially a universal remote control for the microscopic world.
Speaker 2: But instead of an infrared beam turning on a TV,
Speaker 2: you're using a twisted ultrafast laser to flip the fundamental
Speaker 2: symmetry of a crystal on and off.
Speaker 3: The implications for future technologies are immense. We are talking
Speaker 3: about entirely new paradigms for high density data storage, ultrasensitive
Speaker 3: room temperature sensing technologies, and advanced computing architecture. Wow. If
Speaker 3: you can manipulate the fundamental order of a material at
Speaker 3: room temperature using light, you unlock a broad class of
Speaker 3: materials that were previously thought to be completely static and untunable.
Speaker 2: Okay, let's trace this entire journey back, because the physical
Speaker 2: mechanics of what we've covered today are staggering. We started
Speaker 2: with symmetry. Act is the ultimate unbreakable bouncer at the
Speaker 2: club of the microscopic world. It built a cosmic soundproof
Speaker 2: wall between the different vibrations and a crystal.
Speaker 3: A rule we assumed was absolute.
Speaker 2: Absolute, And then we looked at this specific layered crystal
Speaker 2: where electrons bunch up into a charged density wave forming
Speaker 2: these microscopic left and right handed star of David clusters,
Speaker 2: a pattern that just sits there breathing, but is entirely
Speaker 2: invisible to our best electric and magnetic sensors, a.
Speaker 3: Ghost in the lattice until we learned to look at
Speaker 3: it differently.
Speaker 2: Right by using holicity resolved light work screw light, we
Speaker 2: matched the physical twist of our optical screwdriver to the
Speaker 2: microscopic handedness of the material, And once we could finally
Speaker 2: map that ghost, we learned that by tuning the temperature,
Speaker 2: we could essentially dial down the frequency of that breathing
Speaker 2: amplitude on and.
Speaker 3: The moment that frequency perfectly overlapped with an ordinary, forbidden
Speaker 3: lattice vibration.
Speaker 2: We found the secret tunnel, the resonant bridge, the wave
Speaker 2: functions mixed, the rules of symmetry, we're dynamically bypassed, and
Speaker 2: the two isolated rooms suddenly connected. Yes, and the absolute
Speaker 2: best part is that this chiral dressing survives the chaotic
Speaker 2: heat of room temperature. It gives us a way to
Speaker 2: control quantum states with ultrafast lasers right here in the
Speaker 2: real world.
Speaker 3: It really serves as a powerful reminder of how dynamic
Speaker 3: our understanding of the physical world truly is. Modern physics
Speaker 3: is no longer just cataloging the rules of nature. It's
Speaker 3: learning exactly how to find the resonant frequencies that rewrite
Speaker 3: those rules totally. We are bridging the gap between theoretical
Speaker 3: symmetry breaking and the tangible technology of tomorrow.
Speaker 2: It's an incredible shift in perspective, and as we wrap
Speaker 2: up our conversation today, I want to leave you with
Speaker 2: one final thought, tam all over. If scientists can use
Speaker 2: finely tuned light to dynamically bridge forbidden interactions in these
Speaker 2: specific layered crystals, what other unbreakable laws of physics and
Speaker 2: completely different materials might just be waiting for the exact
Speaker 2: right frequency of light to be unlocked. Are there other
Speaker 2: soundproof walls in nature holding back entirely new quantum technologies,
Speaker 2: just waiting for us to find the perfect pitch to
Speaker 2: shatter them.