Seeing the Atom: Quantum Tunneling Microscopy

<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>If you really stop and think about the human condition,
<v Speaker 2>or maybe the scientific condition, it really all boils down
<v Speaker 2>to a refusal to be blind. We have this aggressive,
<v Speaker 2>almost stubborn curiosity. We just can't accept that something is
<v Speaker 2>hidden from us.
<v Speaker 3>Right, It's never enough, never, It's.
<v Speaker 2>Not enough to see the mountain range. We have to
<v Speaker 2>see the rocky. So enough to see the rock, we
<v Speaker 2>need to see the crystal lattice, then the molecule, then
<v Speaker 2>the atom. It's this insatiable need to just peel back
<v Speaker 2>the layers of reality until there's nothing left.
<v Speaker 3>And that drive is I mean, it's pretty much the
<v Speaker 3>engine of our entire technological history. You can draw a
<v Speaker 3>straight line of ambition from the very first clunky glass
<v Speaker 3>lenses back in the sixteen hundreds, which were basically just
<v Speaker 3>polished pebbles, all the way to the smartphone camera in
<v Speaker 3>your pocket, which has more computing power than the Apollo missions.
<v Speaker 2>Incredible when you think about it, that way.
<v Speaker 3>And you can extend that line even further out to
<v Speaker 3>the James Webb Space Telescope sitting out at lagrange point two.
<v Speaker 3>It's all the same impulse reveal the hidden structure. We
<v Speaker 3>just want to see more.
<v Speaker 2>It is. It's this universal desire for I guess higher resolution.
<v Speaker 1>Yeah.
<v Speaker 2>But here's the thing, and this is really the central
<v Speaker 2>conflict of what we're talking about today. For the longest time,
<v Speaker 2>we thought there was a hard stop, a wall, a
<v Speaker 2>physical do not enter sign put up by the universe itself.
<v Speaker 2>We assumed that as you try to look at smaller
<v Speaker 2>and smaller things, specifically when you're using light to do it,
<v Speaker 2>you eventually hit a fundamental boundary, a wall where the
<v Speaker 2>picture just goes and no amount of zooming in is
<v Speaker 2>going to fix it.
<v Speaker 3>That's exactly right, and for a long long time that
<v Speaker 3>boundary seemed absolute. It wasn't a failure of our engineering
<v Speaker 3>or not having enough budget.
<v Speaker 2>It wasn't a skill issue, no, not at all.
<v Speaker 3>It was a failure of the medium itself. The widely
<v Speaker 3>held belief in physics was that the very nature of
<v Speaker 3>light prevented us from seeing the building blocks of matter.
<v Speaker 3>We are talking about Adams the assumption was you cannot
<v Speaker 3>see an atom with.
<v Speaker 2>Light period, which is such a depressing thought. Yeah, but
<v Speaker 2>as you and I both know, impossible is usually just
<v Speaker 2>a challenge waiting for the right group of researchers. Because
<v Speaker 2>today we're discussing a massive breakthrough, something that happened just
<v Speaker 2>a few days ago on January thirty, twenty twenty six.
<v Speaker 3>It's a really fascinating development. Researchers from the University of Regensburg,
<v Speaker 3>specifically their Center for Ultrafastinoscopy, and the University of Birmingham
<v Speaker 3>have well, they've effectively smashed right through that wall.
<v Speaker 2>They publish their findings in Nano letters and the headline is,
<v Speaker 2>I mean, it's essentially this, we can now see the unseeable.
<v Speaker 2>They've achieved optical measurements with atomic resolution.
<v Speaker 3>Which, just to be crystal clear, shouldn't be possible, not
<v Speaker 3>if you follow the classical rules of optics. If you
<v Speaker 3>open a textbook from say ten years ago, it would
<v Speaker 3>tell you this is forbidden.
<v Speaker 2>So today our mission is to explore exactly how they
<v Speaker 2>did it, how they managed to see the unseeable. We're
<v Speaker 2>going to look at that impossible barrier they broke the
<v Speaker 2>surprise discovery, and it involves quantum mechanics that acted as
<v Speaker 2>the key, and and why this changes material science forever.
<v Speaker 3>Yeah, we need to really get into the weeds of
<v Speaker 3>how they managed to turn a barrier into a bridge,
<v Speaker 3>because they didn't just break a rule here, they in
<v Speaker 3>a sense, rewrote the entire rule book.
<v Speaker 2>Okay, so let's start with the problem itself. I want
<v Speaker 2>to understand the enemy. Why can't I just take a
<v Speaker 2>really really strong microscope and zoom in until I see
<v Speaker 2>an atom? I mean, we have powerful lenses. We can
<v Speaker 2>see bacteria, we can see cells. What is physically stopping us.
<v Speaker 3>It's not the lens, that's the thing. It's the light.
<v Speaker 3>The light itself, the light itself. You see in our
<v Speaker 3>daily lives, we tend to think of light as a
<v Speaker 3>straight line, like a laser beam or you know, a
<v Speaker 3>rave sunlight coming through the window.
<v Speaker 1>Right.
<v Speaker 3>Yeah, But fundamentally, light behaves as a wave, and waves
<v Speaker 3>have a specific size a wavelength, right.
<v Speaker 2>Like ripples in a pond have a certain distance between
<v Speaker 2>the crests of each wave exactly.
<v Speaker 3>Now, let's stick with that pond analogy for a second.
<v Speaker 3>Imagine you're standing at the edge of a pond and
<v Speaker 3>you want to detect some hidden object in the water
<v Speaker 3>just by watching how the waves bounce off it. Okay,
<v Speaker 3>if you have a large rock in there and the
<v Speaker 3>waves hit it, they bounce back, they scatter. You can
<v Speaker 3>look at the pattern in the water and say, Aha,
<v Speaker 3>there's a rock there.
<v Speaker 2>Sure the wave hits the rock, it gets disturbed, and
<v Speaker 2>I can see that disturbance, simple enough.
<v Speaker 3>But now what if you're trying to find a tiny
<v Speaker 3>marble and the waves you're sending out are these big
<v Speaker 3>rolling swells. Let's say there're a meter between each crest.
<v Speaker 3>What happens when that big wave hits the tiny marble?
<v Speaker 2>Probably nothing, just rolls right over it. The marble isn't
<v Speaker 2>big enough to disturb the wave at all. It's it's
<v Speaker 2>basically invisible to the wave.
<v Speaker 3>Precisely the wave effectively ignores it. And this is what
<v Speaker 3>we call the diffraction limit. Because light is a wave,
<v Speaker 3>you can't focus it purely down to a single geometric point.
<v Speaker 3>It always spreads out a little bit. You just can't
<v Speaker 3>focus it arbitrarily sharply.
<v Speaker 2>So there's a minimum size to the spot you can
<v Speaker 2>make with light.
<v Speaker 3>Yes, And the consequence of that is that conventional optical microscopes,
<v Speaker 3>the kind you might remember from high school biology or
<v Speaker 3>even the really expensive ones in medical labs. They cannot
<v Speaker 3>resolve structures that are smaller than roughly half the wavelength
<v Speaker 3>of the light they're using.
<v Speaker 2>Okay, so let's put some numbers on this to make
<v Speaker 2>it real. Visible light has a wavelength of what somewhere
<v Speaker 2>between four hundred and seven hundred animeters roughly. Yeah, that's
<v Speaker 2>the range, which means the absolute best resolution you can
<v Speaker 2>possibly get with visible light is maybe two hundred animeters.
<v Speaker 3>Best case scenario. Yes, and an atom is atom is
<v Speaker 3>typically in the range of point one two point three nanometers.
<v Speaker 2>Okay, so the scale is completely off. It's not even close.
<v Speaker 2>We are trying to pick up a single sesame seed
<v Speaker 2>with a bulldozer. The lightweights are literally thousands of times
<v Speaker 2>too fat to feel the atom.
<v Speaker 3>That is the perfect way to visualize it. And that's why,
<v Speaker 3>for the longest time, the very building blocks of matter,
<v Speaker 3>the atoms themselves, were simply beyond direct optical observation. We
<v Speaker 3>literally could not see them with light.
<v Speaker 2>Now, I know what some of our listeners are probably
<v Speaker 2>thinking right now, Who cares about light? We have electron microscopes.
<v Speaker 2>I've seen those black and like pictures of atoms from
<v Speaker 2>electron microscopes. So why is this specific breakthrough with light
<v Speaker 2>so important?
<v Speaker 3>That is a really critical distinction. And yes, you're right.
<v Speaker 3>We do have electron microscopes and scanning tunneling microscopes that
<v Speaker 3>use physical probes, and those are amazing, amazing.
<v Speaker 2>Tool, but they have limitations.
<v Speaker 3>Severe limitations. Electron microscopes, for example, often require a high
<v Speaker 3>vacuum that means you can't look at anything that's wet
<v Speaker 3>or alive volatile, so no biology, really not living biology. No,
<v Speaker 3>And the high energy electrons you use can actually damage
<v Speaker 3>or destroy the very sample you're trying to look at.
<v Speaker 2>So you get the picture, but you might kill the
<v Speaker 2>patient in the process often.
<v Speaker 3>Yes, And those physical probes, the scanning ones, are very
<v Speaker 3>very slow. They literally drag a needle across a surface
<v Speaker 3>line by line.
<v Speaker 2>Like an old dot matrix printer, a very.
<v Speaker 3>Very slow one.
<v Speaker 2>Yes.
<v Speaker 3>Light, on the other hand, is fast, it's generally non destructive,
<v Speaker 3>and most importantly, light interacts with materials in unique ways
<v Speaker 3>that tell us about their chemical and electronic properties. If
<v Speaker 3>we could just see atoms with light, we could learn
<v Speaker 3>things that electron microscopes simply cannot tell us.
<v Speaker 2>So the goal has always been this kind of holy grail.
<v Speaker 2>Can we get the resolution of an electron microscope but
<v Speaker 2>with the versatility and the speed of light.
<v Speaker 3>That has been the dream, and that is exactly what
<v Speaker 3>this team from Regensburg and Birmingham went hunting for.
<v Speaker 2>So let's talk about their setup. They knew they couldn't
<v Speaker 2>just use a normal lens because of that diffraction limit
<v Speaker 2>we just talked about. So how did they try to
<v Speaker 2>cheat the system? What was the work around?
<v Speaker 3>Their approach falls under a category of science called near
<v Speaker 3>field optics. The basic idea is, if the problem is
<v Speaker 3>that lightweights are too big when they're traveling through free
<v Speaker 3>space what we call the far field, right, the solution
<v Speaker 3>is to manipulate the light right up against the object
<v Speaker 3>you want.
<v Speaker 2>To look at, so get up close and personal. You
<v Speaker 2>eliminate the travel distance where it can spread out extremely close.
<v Speaker 3>They used a setup that involves a very sharp metal tip.
<v Speaker 3>Now when I say sharp, I don't mean like a
<v Speaker 3>needle you'd sew with. I mean atomically sharp.
<v Speaker 2>Atomically sharp. What does that even mean? In practice?
<v Speaker 3>It means the radius of curvature at the very apex
<v Speaker 3>of this tip is typically about ten nanometers ten animeters.
<v Speaker 2>Okay, for context, a human hair is roughly eighty thousand
<v Speaker 2>to one hundred thousand nanometers wide, So this tip is
<v Speaker 2>thousands of times sharper than a single hair.
<v Speaker 3>It is, and the technique involves bringing this tip extraordinarily
<v Speaker 3>close to the surface of the material they want to study,
<v Speaker 3>hovering just above it.
<v Speaker 2>So they have this nanometer sharp needle floating over a sample. Yeah,
<v Speaker 2>then what do they just shine a light on it
<v Speaker 2>and hope for the best.
<v Speaker 3>Yes, but with a clever twist, they use a continuous
<v Speaker 3>wave laser to illuminate the whole system. Now, normally that
<v Speaker 3>light would just hit the surface and bounce off, and
<v Speaker 3>you'd be stuck with the same.
<v Speaker 2>Old diffraction limit, the bulldozer problem again exactly.
<v Speaker 3>But because that sharp metal tip is there, something really
<v Speaker 3>interesting happens. The system squeezes the infrared light into the
<v Speaker 3>tiny gap between the tip and.
<v Speaker 2>The sample, squeezing light. I love that image. It sounds
<v Speaker 2>like they are physically forcing the light to be smaller
<v Speaker 2>than it wants to be, like putting a corset on
<v Speaker 2>a photon.
<v Speaker 3>That's a fair way to visualize it. It's a phenomenon
<v Speaker 3>called plasmonic nanofocusing. The presence of the metal tip acts
<v Speaker 3>like a lightning rod or an antenna, and it concentrates
<v Speaker 3>the light field right at its apex.
<v Speaker 2>So it's a funnel.
<v Speaker 3>It's a perfect funnel for light. It confines the energy
<v Speaker 3>and by doing this they completely bypass the diffraction limit
<v Speaker 3>because the light isn't traveling freely anymore. It's trapped in
<v Speaker 3>this tiny, tiny cavity.
<v Speaker 2>So by confining the light to the very end of
<v Speaker 2>the tip, the resolution of the picture you take is
<v Speaker 2>no longer determined by the wavelength of the light, but
<v Speaker 2>by the size of the tip exactly.
<v Speaker 3>The resolution becomes roughly the size of the tip's apex.
<v Speaker 3>In this case that's about ten nanometers, which is huge.
<v Speaker 2>Right, I mean, going from two hundred nanometers down to
<v Speaker 2>ten ananimeters is a massive jump.
<v Speaker 3>Oh, it's a dramatic improvement. This technique, in its early
<v Speaker 3>stages is called near field optical tunneling emission, and getting
<v Speaker 3>down to ten nanometers is a massive victory for optical microscopy.
<v Speaker 3>It allows you to see things like large molecules, proteins,
<v Speaker 3>that kind of thing.
<v Speaker 2>But and there is always a butt in these stories,
<v Speaker 2>isn't there always ten nanometers is still not an atom correct?
<v Speaker 3>As we establish, atoms are generally in that zero point
<v Speaker 3>one two point three nanometer range. So while ten nanometers
<v Speaker 3>is incredibly small, it's still about a factor of three
<v Speaker 3>alreaty two coarse to see an individual atom.
<v Speaker 2>It's like trying to type on a smartphone keyboard while
<v Speaker 2>you're wearing boxing gloves. You know the keys are there,
<v Speaker 2>but your finger, or in this case, the tip is
<v Speaker 2>just too wide to hit one at a time.
<v Speaker 3>That is a perfect analogy. If you scan a grid
<v Speaker 3>of atoms with a ten nanimeter wide tip, you are
<v Speaker 3>effectively averaging the signal from dozens, maybe hundreds of atoms,
<v Speaker 3>all at once. The image you get just looks like
<v Speaker 3>a smooth surface. You can't see the individual bumps, you
<v Speaker 3>can't see the lattice structure.
<v Speaker 2>So up until January thirtieth of this year, the consensus
<v Speaker 2>was essentially this is as good as it gets. You
<v Speaker 2>can squeeze light down to the size of your tip,
<v Speaker 2>but you can't really make the tip smaller than about
<v Speaker 2>ten nanimeters because well, metal isn't infinitely strong. You run
<v Speaker 2>into physical limits, right.
<v Speaker 3>You run into structural limits of the material itself. So
<v Speaker 3>they had a great microftote had an amazing microscope, but
<v Speaker 3>it wasn't an atomic microscope.
<v Speaker 2>And this is where the story gets really good because
<v Speaker 2>typically in science, when you hit a physical limit, like
<v Speaker 2>the size of your tool, you sort of accept it
<v Speaker 2>and work around it. But this team, led by the
<v Speaker 2>researchers at the Regensburg Center for Ultra Fastinoscopy, they were
<v Speaker 2>determined to find the absolute limit.
<v Speaker 3>They wanted to know what happens if you just keep pushing, So.
<v Speaker 2>They started moving the tip closer and closer to the
<v Speaker 2>surface just to see what would happen to that confined
<v Speaker 2>light as the gap got smaller and smaller.
<v Speaker 3>Yeah, and we are talking about closing the gap down
<v Speaker 3>to atomic dimensions. Here they are hovering a sharp metal spike,
<v Speaker 3>maybe a single atom's width away from the surface.
<v Speaker 2>That sounds incredibly risky. Yeah, And what happens if you
<v Speaker 2>touch the surface? Do you just crash the machine?
<v Speaker 3>You absolutely crash the tip, you blunt it, you ruin
<v Speaker 3>the sample. The experiments over. It's like trying to fly
<v Speaker 3>a helicopter six inches off the ground in the middle
<v Speaker 3>of a hurricane. It requires an immense amount of stability
<v Speaker 3>and precision, but.
<v Speaker 2>They did it. They kept reducing the distance between the
<v Speaker 2>tip and the sample until it was comparable to the
<v Speaker 2>spacing between individual atoms.
<v Speaker 3>This is where the AHA moment happens. I was reading
<v Speaker 3>the account from Felix Shiell, one of the lead authors
<v Speaker 3>from the University of Regensburg. He described it almost like
<v Speaker 3>a shock.
<v Speaker 2>Yeah. He noted that at these very very small distances,
<v Speaker 2>the signal, the light that was coming back from that
<v Speaker 2>tiny gap, it just shot up dramatically. It wasn't a
<v Speaker 2>gradual increase, it was a massive spike.
<v Speaker 3>And he said, and this is the quote, we didn't
<v Speaker 3>immediately understand what was happening. That is the most exciting
<v Speaker 3>sentence in all of science. It's never eureka, it's.
<v Speaker 2>Huh, that's weird. That's weird. Usually proceeds either a Nobel
<v Speaker 2>prize or a laboratory fire, in this case, hopefully the former.
<v Speaker 3>Hopefully they realized that when that signal spiked, the resolution
<v Speaker 3>of their image suddenly sharpened. I mean drastically.
<v Speaker 2>You weren't seeing those ten nanimeter blobs anymore.
<v Speaker 3>No, they were suddenly resolving features down to point one nanimeters.
<v Speaker 2>Zero point one nanometers, that is the atomic scale. They
<v Speaker 2>were suddenly seeing the atoms they were.
<v Speaker 3>They had inadvertently accidentally broken the barrier. But the question,
<v Speaker 3>of course, was how their tip was still ten nanometers wide.
<v Speaker 3>How could a ten nanometer tip possibly take a zero
<v Speaker 3>point one nanometer picture?
<v Speaker 1>Right?
<v Speaker 2>I mean, let's go back to our boxing glove analogy. Yeah,
<v Speaker 2>how did the boxing gloves suddenly turn into a needle.
<v Speaker 2>The glove didn't.
<v Speaker 3>Change size, the glove didn't change, but the physics of
<v Speaker 3>the interaction changed. And this is why we're here today.
<v Speaker 3>The answer lies in quantum mechanics.
<v Speaker 2>Okay, let's unpack this. This is where we need to
<v Speaker 2>be really careful, because quantum mechanics is usually where our
<v Speaker 2>everyday intuition goes to die. How does a quantum effect
<v Speaker 2>turn a ten nanometer flashlight into an atomic spotlight?
<v Speaker 3>It all has to do with what happens in that tiny,
<v Speaker 3>tiny gap between the tip and the sample. Now, in
<v Speaker 3>the classical world, the world of baseballs and planets, if
<v Speaker 3>you hold a ball close to a wall, but you
<v Speaker 3>don't touch it, the ball stays in your hand, there
<v Speaker 3>is a gap. Nothing closses it.
<v Speaker 2>Right, almost touching is still not touching, the circuit is open,
<v Speaker 2>no electricity flows.
<v Speaker 3>But in the quantum world, things are well, they're fuzzier.
<v Speaker 3>Electrons Specifically, they have a probability of being in different
<v Speaker 3>places at once. They aren't just hard little marbles. They
<v Speaker 3>are more like probability clouds. Okay, And if you bring
<v Speaker 3>two conductive materials close enough together, like the metal tip
<v Speaker 3>and the sample surface, the edge of the electron cloud
<v Speaker 3>in the tip starts to actually overlap with the sample.
<v Speaker 2>So even though there is still empty space between them, physically,
<v Speaker 2>the electron can sort of bridge that gap.
<v Speaker 3>Exactly, there is a non zero probability that an electron
<v Speaker 3>can simply appear on the other side. It doesn't travel
<v Speaker 3>through the space, It tunnels through the barrier of empty space.
<v Speaker 3>It's a purely quantum effect.
<v Speaker 2>Okay, so we have electrons tunneling. I've heard of scanning
<v Speaker 2>tunneling microscopes, so that part makes sense. But tunneling usually
<v Speaker 2>just creates an electrical current. How does that create light?
<v Speaker 2>And more importantly, how does it create this super resolution light.
<v Speaker 3>This is where the laser comes back into play. Remember
<v Speaker 3>they are constantly shining that infrared laser on the whole system.
<v Speaker 3>Light is an electromagnetic wave. That means it consists of
<v Speaker 3>an an oscillating electric field. It pushes and it pulls
<v Speaker 3>on charged particles like electrons.
<v Speaker 2>So the light is providing this rhythmic push pull push pull.
<v Speaker 3>Correct, This infrared light creates a continuously oscillating electric field
<v Speaker 3>right in that tiny gap, and it acts as a driver.
<v Speaker 3>This field forces the electrons to leap back and forth
<v Speaker 3>between the apex atom of the tip and the sample.
<v Speaker 2>So the light is like a pump or maybe a
<v Speaker 2>conductor's baton, setting the rhythm it.
<v Speaker 3>Conductor's baton is a great way to think of it.
<v Speaker 3>It drives the rhythm. The electrons are tunneling back and forth,
<v Speaker 3>but they're doing it in perfect time with the frequency
<v Speaker 3>of the laser light.
<v Speaker 2>Okay, so we have electrons jumping back and forth across
<v Speaker 2>this gap in time with the laser. I'm still missing
<v Speaker 2>the last step. How does that help us see anything.
<v Speaker 3>This is where the antenna analogy they use in the
<v Speaker 3>paper comes in, and it's perfect. Think about how a
<v Speaker 3>simple radio antenna works. You drive electrons up and down
<v Speaker 3>a metal rod with an electrical signal, and that acceleration
<v Speaker 3>of electrons generates radio waves, it generates an electromagnetic signal.
<v Speaker 2>Moving electrons create electromagnetic waves. That's physics, one.
<v Speaker 3>On one right exactly now, in this experiment, the electrons
<v Speaker 3>that are tunneling back and forth between the tip and
<v Speaker 3>the sample, they're doing the exact same thing. They are
<v Speaker 3>acting like a tiny, single atom sized antenna, and their
<v Speaker 3>motion produces its own faint electromagnetic signal, a little pulse
<v Speaker 3>of light.
<v Speaker 2>Essentially, wait a second, stop, this is the part that
<v Speaker 2>I want to make absolutely sure I'm getting the light
<v Speaker 2>that they are detecting. It isn't the laser light bouncing
<v Speaker 2>off the atom.
<v Speaker 3>No, and that is the absolute critical distinction. The light
<v Speaker 3>they detect is what they call the near field optical
<v Speaker 3>tunneling emission. It is light that is generated by the
<v Speaker 3>electrons motion as it tunnels back and forth.
<v Speaker 2>That is mind blowing. So the laser isn't the illumination
<v Speaker 2>the lasers the engine. The electron itself is the light bulb.
<v Speaker 3>That is a beautiful way to put it. The laser
<v Speaker 3>drives the electron, and the electron then broadcasts its own
<v Speaker 3>position by emitting light.
<v Speaker 2>Okay, okay, but why does this solve the fat finger problem?
<v Speaker 2>The boxing glove problem. Why is the resolution so unbelievably.
<v Speaker 3>Good Because quantum tunneling is incredibly sensitive to distance, I
<v Speaker 3>mean exponentially sensitive. If you move the tip just a
<v Speaker 3>tiny tiny bit further away, even just half an atom's
<v Speaker 3>with the probability of an electron tunneling drops to almost zero.
<v Speaker 3>It just stops.
<v Speaker 2>So the tunneling only happens at the absolute closest point
<v Speaker 2>between a tip and the sample.
<v Speaker 3>Yes, think about the geometry of the tip. It's a curve, right, Yeah,
<v Speaker 3>even though the metal tip is ten nanimeters wide. Overall,
<v Speaker 3>the only place that is close enough to the sample
<v Speaker 3>to allow tunneling is the single atom at the very
<v Speaker 3>very apex of that curve. The atoms right next to
<v Speaker 3>it on the tip are just slightly further away, and
<v Speaker 3>for tunneling, slightly is everything.
<v Speaker 2>So the active part of the sensor effectively shrinks from
<v Speaker 2>the whole ten nanimeter tip down to just that one
<v Speaker 2>final atom.
<v Speaker 3>At the point precisely. The rest of the tip is silent,
<v Speaker 3>it's too far away. Only that one single atom is
<v Speaker 3>broadcasting the signal. Yeah, that is how they get point
<v Speaker 3>one nimes resolution from a ten nanimeter object.
<v Speaker 2>That is just it's incredibly clever. You're using the geometry
<v Speaker 2>and the rules of quantum probability to filter out everything
<v Speaker 2>except the signal from a single point.
<v Speaker 3>It creates a virtual probe that is much much smaller
<v Speaker 3>than the physical probe you're using.
<v Speaker 2>There was a stat in the research that just completely
<v Speaker 2>floored me. Doctor Tom Saiday from the University of Birmingham.
<v Speaker 2>He was trying to explain the sensitivity of this measurement.
<v Speaker 2>He said, and I'm quoting here, just one electron moving
<v Speaker 2>over a distance smaller than the size of an atom
<v Speaker 2>every hundred cycles of the.
<v Speaker 3>Light can already produce light that is strong enough for
<v Speaker 3>us to detect.
<v Speaker 2>That is absurd. One electron every hundred times the light
<v Speaker 2>wave oscillates. I mean, we talk about precision measurement, but
<v Speaker 2>that sounds like it's straight out of science fiction.
<v Speaker 3>It really highlights just how powerful this technique is. We're
<v Speaker 3>not blasting the sample with high energy to get a signal.
<v Speaker 3>We are tuning in and listening to the electromagnetic whisper
<v Speaker 3>of a single particle doing its quantum dance.
<v Speaker 2>What does this all mean for what we are actually seeing.
<v Speaker 2>You mentioned earlier that we aren't taking a picture in
<v Speaker 2>the traditional sense. If I look at the data coming
<v Speaker 2>out of this machine, am I seeing a photograph of
<v Speaker 2>a bunch of atoms?
<v Speaker 3>Not exactly a photograph. No. Valentin Berkbauer from the University
<v Speaker 3>of Regensburg, he put it really well. He said, we
<v Speaker 3>are no longer limited by how tightly light can be confined. Instead,
<v Speaker 3>what we're doing is directly controlling and measuring quantum electron motion.
<v Speaker 2>Okay, so translate that for me. If I'm looking at
<v Speaker 2>the screen, what is the image that I'm seeing actually
<v Speaker 2>telling me?
<v Speaker 3>You are seeing a map, But it's a map of
<v Speaker 3>probability and conductivity because the signal you detect depends entirely
<v Speaker 3>on electrons being able to tunnel. It tells you how
<v Speaker 3>easy it is for electrons to move at that specific
<v Speaker 3>point in the material.
<v Speaker 2>So it's a map of how well electricity flows. But
<v Speaker 2>at the level of a single atom.
<v Speaker 3>Yes, you are measuring the materials local conductivity with atomic
<v Speaker 3>scale precision, and that is incredibly valuable information because conductivity
<v Speaker 3>isn't always uniform, especially in advanced materials. You might have
<v Speaker 3>defects or impurities, or specific atomic arrangements that conduct better
<v Speaker 3>or worse than the atoms next to them. This tool
<v Speaker 3>lets you see those variations atom by atom.
<v Speaker 2>The paper says this pushes optical microscopy to length scales
<v Speaker 2>nearly one hundred thousand times smaller than conventional light based microscopes.
<v Speaker 2>That number is just staggering to even think about.
<v Speaker 3>It completely redefines the field. We are moving from simply
<v Speaker 3>observing the shape of things to observing the behavior of
<v Speaker 3>things at the most fundamental quantum level.
<v Speaker 2>Now here's where it gets really interesting for the people
<v Speaker 2>listening who might work in labs or follow technology trends.
<v Speaker 2>Usually when we hear about a breakthrough like this atomic
<v Speaker 2>resolution quantum tunneling, my brain immediately goes to one place. Okay,
<v Speaker 2>that sounds expensive. I'm imagining a machine the size of
<v Speaker 2>a room that costs fifty million dollars and requires a
<v Speaker 2>team of twelve PhDs just to turn on.
<v Speaker 3>That is the standard assumption. And you know, usually you
<v Speaker 3>would be absolutely right. In the past you get anywhere
<v Speaker 3>near this kind of temporal or spatial resolution, you needed
<v Speaker 3>what are called ultrafast lasers, right, and these are incredibly complex, finicky,
<v Speaker 3>and very very expensive pieces of equipment that produce ultra
<v Speaker 3>short pulses of light pulses that last only for femtoseconds, and.
<v Speaker 2>A femtosecond is a quadrillianth of a.
<v Speaker 3>Second quadrilliant of a second. Yes, and maintaining a laser
<v Speaker 3>that can do that consistently is a nightmare. It's like
<v Speaker 3>owning a Formula one car. It's incredibly fast, but it
<v Speaker 3>spends half its life in the garage being tuned by specialists.
<v Speaker 2>But I feel a butt coming.
<v Speaker 3>But this team did it all with a standard continuous
<v Speaker 3>wave laser.
<v Speaker 2>Standard as in as in.
<v Speaker 3>The kind of laser technology that is widespread, robust, and
<v Speaker 3>relatively affordable. A continuous wave laser just emits a steady,
<v Speaker 3>constant beam of light. It's not pulsing at femt too
<v Speaker 3>second speeds. It's simple.
<v Speaker 2>Why is that such a big deal? I mean, apart
<v Speaker 2>from just saving money on the initial purchase.
<v Speaker 3>It democratizes the science. It's all about accessibility. If you
<v Speaker 3>need a five million dollar laser setup to do this
<v Speaker 3>kind of work, then only a handful of elite labs
<v Speaker 3>in the world can ever verify your results or use
<v Speaker 3>the technique to discover new things.
<v Speaker 2>But if you can do it with a standard laser setup.
<v Speaker 3>Suddenly, thousands of labs around the world can potentially implement this.
<v Speaker 3>It dramatically lowers the barrier to.
<v Speaker 2>Entry, which accelerates the rate of discovery across the board exactly.
<v Speaker 3>The simplicity of this setup I mean simplicity is relative.
<v Speaker 3>Of course, we're still talking about very advanced optics. But
<v Speaker 3>that relative simplicity means this technique could become a standard
<v Speaker 3>tool in material science much much faster than if it
<v Speaker 3>required exotic, expensive gear.
<v Speaker 2>So we might see this popping up in university labs,
<v Speaker 2>in corporate R and D centers much sooner than we'd think.
<v Speaker 3>That is absolutely the hope. The researchers themselves explicitly mentioned
<v Speaker 3>that this simplicity could help make the technique more widely accessible.
<v Speaker 3>It's the difference between a tool that only exists at
<v Speaker 3>a place like CERN and a tool that can exist
<v Speaker 3>at every research university.
<v Speaker 2>I want to zoom out a bit now. Pun definitely intended.
<v Speaker 2>We've talked about the how and the what. Let's really
<v Speaker 2>dig into the why. Why do we need to see
<v Speaker 2>atoms this? Clearly? What does this unlock for the future.
<v Speaker 3>The source material touches on this, and I think it's
<v Speaker 3>the most exciting part. It's all about the connection between
<v Speaker 3>the micro and the macro.
<v Speaker 2>Okay, connect those dots for me. What does that mean?
<v Speaker 3>Think about any advanced material you use every day. The
<v Speaker 3>screen on your phone, the battery in your electric car,
<v Speaker 3>the solar panel on your roof. All of these things
<v Speaker 3>have what we call macroscopic properties.
<v Speaker 2>Right, the screen is tough but transparent, The battery holds
<v Speaker 2>a charge efficiently, the solar panel absorbs sunlight. Well, those
<v Speaker 2>are the things we actually experience. It's the user interface.
<v Speaker 3>Of reality exactly. But every single one of those macroscopic
<v Speaker 3>properties is determined entirely by what's happening at the microscopic scale,
<v Speaker 3>specifically how the atoms are arranged and how they interact
<v Speaker 3>with each other and with light.
<v Speaker 2>So if a solar panel isn't as efficient as.
<v Speaker 3>It could be, often because of something going wrong at
<v Speaker 3>the atomic level, Right at the moment where the photon
<v Speaker 3>hits the material and is supposed to create an electron
<v Speaker 3>hole pair. Maybe the electron gets stuck at a defect
<v Speaker 3>in the crystal lattice, Maybe it recombines too quickly and
<v Speaker 3>the energy is lost as heat.
<v Speaker 2>So if we want to build better, more efficient solar panels.
<v Speaker 2>We need to be able to see exactly what's going
<v Speaker 2>wrong or what's going right at that single atom level precisely.
<v Speaker 3>This new approach allows scientists to study how materials interact
<v Speaker 3>with light at the scale of individual atoms. We can
<v Speaker 3>finally see the quantum machinery that drives the everyday world
<v Speaker 3>we live in.
<v Speaker 2>It's like trying to fix a car engine. Before we
<v Speaker 2>could only look at the engine block from ten feet
<v Speaker 2>away and listen to it. Now we can basically open
<v Speaker 2>it up, stick our head inside the cylinder and watch
<v Speaker 2>the individual valves moving.
<v Speaker 3>And not just look at them. We can see how
<v Speaker 3>they're moving in real time. We can measure the dynamics.
<v Speaker 3>This is why the center in Reagansbird is called this
<v Speaker 3>Center for Ultrafast Nanoscopy. It's not a still phototures the action.
<v Speaker 2>How does do that well?
<v Speaker 3>Because the electron tunneling is being driven by the cycles
<v Speaker 3>of the laser light, the time resolution of the measurement
<v Speaker 3>is incredibly high, on the order of femtoseconds, So.
<v Speaker 2>We can actually make movies of electrons moving.
<v Speaker 3>In a sense, yes, we can capture the dynamics of
<v Speaker 3>how electrons move through a crystal lattice. How they respond
<v Speaker 3>to light with an unbelievable combination of spatial and temporal resolution.
<v Speaker 2>That's just wild. I also want to give a shout
<v Speaker 2>out here to the human element. This wasn't some solo
<v Speaker 2>genius toiling away in a basement. This was a deep
<v Speaker 2>collaboration between the University of Regensburg in Germany and the
<v Speaker 2>University of Birmingham in the UK.
<v Speaker 3>Oh. Absolutely, science at this level is increasingly a team sport.
<v Speaker 3>You had the experimental expertise in Regensburg, the people who
<v Speaker 3>physically build the setup, create the tip, align the lasers,
<v Speaker 3>and you had the crucial theoretical contributions from Birmingham, people
<v Speaker 3>like doctor Tom Saide, Felix Schiegel, Valentin Bergbauer. It really
<v Speaker 3>does take a village to see.
<v Speaker 2>An adam, It really does. And I have to mend
<v Speaker 2>the visual they released with the paper. I know this
<v Speaker 2>is an audio format, but the artistic representation they had,
<v Speaker 2>done by an artist named Brad Baxley, is so cool.
<v Speaker 2>It shows these bright glowing spheres, the electrons leaping back
<v Speaker 2>and forth between the sharp point of the tip and
<v Speaker 2>the flat sample below. It really drives home that we
<v Speaker 2>aren't looking at static rocks anymore, We're looking at a dynamic,
<v Speaker 2>buzzing gants of quantum particles.
<v Speaker 3>It helps visualize the invisible, and that is really the
<v Speaker 3>core of what this discovery is all about. It changes
<v Speaker 3>our fundamental mental model of the material world.
<v Speaker 2>Okay, so let's try to recap the journey we've been
<v Speaker 2>on today. This has been a dense one, but I
<v Speaker 2>think the payoff is absolutely huge.
<v Speaker 3>We started with the diffraction limit, this old idea that
<v Speaker 3>light waves are just too big and clumsy to see
<v Speaker 3>something as small as an atom, a fundamental wall of
<v Speaker 3>physics that stood for centuries.
<v Speaker 2>Then we introduced the heroes of our story, the team
<v Speaker 2>from Regensburg and Birmingham, who decided to cheat. They decided
<v Speaker 2>to squeeze light into a tiny gap beneath the sharp
<v Speaker 2>metal tip, using this idea of near field optics.
<v Speaker 3>And they kept pushing that tip closer to the absolute
<v Speaker 3>limit until the classical world gave way and the quantum
<v Speaker 3>world took.
<v Speaker 2>Over, which led to that complete surprise that that's weird moment.
<v Speaker 2>Quantum tunneling allowed them to use a simple standard laser
<v Speaker 2>to drive electrons back and forth, effectively turning a single
<v Speaker 2>atom into a broadcast antenna.
<v Speaker 3>Resulting in an unbelievable zero point one nanometer resolution, true
<v Speaker 3>atomic vision, and a way to measure a material's conductivity
<v Speaker 3>with a precision we've never had before.
<v Speaker 2>And maybe most importantly for the future of science, they
<v Speaker 2>did it all with equipment that is surprisingly accessible, which
<v Speaker 2>opens the door for a revolution in how we study
<v Speaker 2>and design new materials.
<v Speaker 3>It's a classic scientific story. Really, you hit a wall,
<v Speaker 3>so you figure out how to dig a tunnel under it,
<v Speaker 3>in this case literally a quantum tunnel.
<v Speaker 2>I love that, and I really liked the phrase they
<v Speaker 2>used in their paper to describe it, atomic scale telegraphy
<v Speaker 2>with light.
<v Speaker 3>It fits perfectly, doesn't it. We are literally tapping out
<v Speaker 3>messages using single electrons as the messengers, dot dash dot.
<v Speaker 2>It really forces you to reconsider what we even mean
<v Speaker 2>when we say fundamental limitations.
<v Speaker 3>It does. It's a good reminder that fundamental often just
<v Speaker 3>means we haven't figured out the cleve workaround yet.
<v Speaker 2>And that's really where I want to leave our listeners today.
<v Speaker 2>We all grow up learning these hard and fast rules.
<v Speaker 2>You can't go faster than light, you can't see atoms
<v Speaker 2>with light, you can't be in two places at once,
<v Speaker 2>and yet.
<v Speaker 3>Quantum mechanics seems to view these rules more as suggestions,
<v Speaker 3>or at the very least as puzzles to be solved
<v Speaker 3>in interesting ways.
<v Speaker 2>Exactly, we just learned how we used light something huge
<v Speaker 2>in wave like to prod single electrons, and that those
<v Speaker 2>electrons shatted back loud enough for us to hear them.
<v Speaker 2>It just makes you wonder what other impossible barriers are
<v Speaker 2>just sitting there, waiting for the right trick to write,
<v Speaker 2>atomically sharp tip, or the right happy accident to be
<v Speaker 2>broken wide open.
<v Speaker 3>Perhaps the limit isn't in the physics at all, but
<v Speaker 3>just in our imagination of how to.
<v Speaker 2>Apply a profound thought to end on. Thanks for exploring
<v Speaker 2>this breakthrough with us, Keep questioning the limit, and keep
<v Speaker 2>looking closer. See you next time.