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Seeing the Atom: Quantum Tunneling Microscopy · The Quark Side - Quantum Physics Podcast

• 0:01
  Speaker 1: Welcome to the quart Side Quantum Physics podcast, an exploration
• 0:05
  Speaker 1: of 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 really stop and think about the human condition,
• 0:32
  Speaker 2: or maybe the scientific condition, it really all boils down
• 0:37
  Speaker 2: to a refusal to be blind. We have this aggressive,
• 0:42
  Speaker 2: almost stubborn curiosity. We just can't accept that something is
• 0:46
  Speaker 2: hidden from us.
• 0:46
  Speaker 3: Right, It's never enough, never, It's.
• 0:48
  Speaker 2: Not enough to see the mountain range. We have to
• 0:50
  Speaker 2: see the rocky. So enough to see the rock, we
• 0:52
  Speaker 2: need to see the crystal lattice, then the molecule, then
• 0:54
  Speaker 2: the atom. It's this insatiable need to just peel back
• 0:59
  Speaker 2: the layers of reality until there's nothing left.
• 1:02
  Speaker 3: And that drive is I mean, it's pretty much the
• 1:04
  Speaker 3: engine of our entire technological history. You can draw a
• 1:07
  Speaker 3: straight line of ambition from the very first clunky glass
• 1:11
  Speaker 3: lenses back in the sixteen hundreds, which were basically just
• 1:14
  Speaker 3: polished pebbles, all the way to the smartphone camera in
• 1:17
  Speaker 3: your pocket, which has more computing power than the Apollo missions.
• 1:20
  Speaker 2: Incredible when you think about it, that way.
• 1:21
  Speaker 3: And you can extend that line even further out to
• 1:24
  Speaker 3: the James Webb Space Telescope sitting out at lagrange point two.
• 1:27
  Speaker 3: It's all the same impulse reveal the hidden structure. We
• 1:30
  Speaker 3: just want to see more.
• 1:32
  Speaker 2: It is. It's this universal desire for I guess higher resolution.
• 1:36
  Speaker 1: Yeah.
• 1:37
  Speaker 2: But here's the thing, and this is really the central
• 1:40
  Speaker 2: conflict of what we're talking about today. For the longest time,
• 1:43
  Speaker 2: we thought there was a hard stop, a wall, a
• 1:45
  Speaker 2: physical do not enter sign put up by the universe itself.
• 1:49
  Speaker 2: We assumed that as you try to look at smaller
• 1:51
  Speaker 2: and smaller things, specifically when you're using light to do it,
• 1:56
  Speaker 2: you eventually hit a fundamental boundary, a wall where the
• 1:58
  Speaker 2: picture just goes and no amount of zooming in is
• 2:02
  Speaker 2: going to fix it.
• 2:03
  Speaker 3: That's exactly right, and for a long long time that
• 2:05
  Speaker 3: boundary seemed absolute. It wasn't a failure of our engineering
• 2:09
  Speaker 3: or not having enough budget.
• 2:10
  Speaker 2: It wasn't a skill issue, no, not at all.
• 2:12
  Speaker 3: It was a failure of the medium itself. The widely
• 2:15
  Speaker 3: held belief in physics was that the very nature of
• 2:18
  Speaker 3: light prevented us from seeing the building blocks of matter.
• 2:21
  Speaker 3: We are talking about Adams the assumption was you cannot
• 2:25
  Speaker 3: see an atom with.
• 2:26
  Speaker 2: Light period, which is such a depressing thought. Yeah, but
• 2:29
  Speaker 2: as you and I both know, impossible is usually just
• 2:32
  Speaker 2: a challenge waiting for the right group of researchers. Because
• 2:34
  Speaker 2: today we're discussing a massive breakthrough, something that happened just
• 2:38
  Speaker 2: a few days ago on January thirty, twenty twenty six.
• 2:42
  Speaker 3: It's a really fascinating development. Researchers from the University of Regensburg,
• 2:46
  Speaker 3: specifically their Center for Ultrafastinoscopy, and the University of Birmingham
• 2:51
  Speaker 3: have well, they've effectively smashed right through that wall.
• 2:54
  Speaker 2: They publish their findings in Nano letters and the headline is,
• 2:58
  Speaker 2: I mean, it's essentially this, we can now see the unseeable.
• 3:01
  Speaker 2: They've achieved optical measurements with atomic resolution.
• 3:04
  Speaker 3: Which, just to be crystal clear, shouldn't be possible, not
• 3:08
  Speaker 3: if you follow the classical rules of optics. If you
• 3:11
  Speaker 3: open a textbook from say ten years ago, it would
• 3:14
  Speaker 3: tell you this is forbidden.
• 3:15
  Speaker 2: So today our mission is to explore exactly how they
• 3:18
  Speaker 2: did it, how they managed to see the unseeable. We're
• 3:21
  Speaker 2: going to look at that impossible barrier they broke the
• 3:23
  Speaker 2: surprise discovery, and it involves quantum mechanics that acted as
• 3:27
  Speaker 2: the key, and and why this changes material science forever.
• 3:31
  Speaker 3: Yeah, we need to really get into the weeds of
• 3:33
  Speaker 3: how they managed to turn a barrier into a bridge,
• 3:35
  Speaker 3: because they didn't just break a rule here, they in
• 3:38
  Speaker 3: a sense, rewrote the entire rule book.
• 3:41
  Speaker 2: Okay, so let's start with the problem itself. I want
• 3:43
  Speaker 2: to understand the enemy. Why can't I just take a
• 3:47
  Speaker 2: really really strong microscope and zoom in until I see
• 3:50
  Speaker 2: an atom? I mean, we have powerful lenses. We can
• 3:54
  Speaker 2: see bacteria, we can see cells. What is physically stopping us.
• 3:58
  Speaker 3: It's not the lens, that's the thing. It's the light.
• 4:00
  Speaker 3: The light itself, the light itself. You see in our
• 4:04
  Speaker 3: daily lives, we tend to think of light as a
• 4:06
  Speaker 3: straight line, like a laser beam or you know, a
• 4:09
  Speaker 3: rave sunlight coming through the window.
• 4:11
  Speaker 1: Right.
• 4:12
  Speaker 3: Yeah, But fundamentally, light behaves as a wave, and waves
• 4:16
  Speaker 3: have a specific size a wavelength, right.
• 4:19
  Speaker 2: Like ripples in a pond have a certain distance between
• 4:22
  Speaker 2: the crests of each wave exactly.
• 4:24
  Speaker 3: Now, let's stick with that pond analogy for a second.
• 4:27
  Speaker 3: Imagine you're standing at the edge of a pond and
• 4:29
  Speaker 3: you want to detect some hidden object in the water
• 4:32
  Speaker 3: just by watching how the waves bounce off it. Okay,
• 4:34
  Speaker 3: if you have a large rock in there and the
• 4:36
  Speaker 3: waves hit it, they bounce back, they scatter. You can
• 4:39
  Speaker 3: look at the pattern in the water and say, Aha,
• 4:41
  Speaker 3: there's a rock there.
• 4:42
  Speaker 2: Sure the wave hits the rock, it gets disturbed, and
• 4:44
  Speaker 2: I can see that disturbance, simple enough.
• 4:47
  Speaker 3: But now what if you're trying to find a tiny
• 4:49
  Speaker 3: marble and the waves you're sending out are these big
• 4:52
  Speaker 3: rolling swells. Let's say there're a meter between each crest.
• 4:56
  Speaker 3: What happens when that big wave hits the tiny marble?
• 4:59
  Speaker 2: Probably nothing, just rolls right over it. The marble isn't
• 5:02
  Speaker 2: big enough to disturb the wave at all. It's it's
• 5:05
  Speaker 2: basically invisible to the wave.
• 5:07
  Speaker 3: Precisely the wave effectively ignores it. And this is what
• 5:11
  Speaker 3: we call the diffraction limit. Because light is a wave,
• 5:14
  Speaker 3: you can't focus it purely down to a single geometric point.
• 5:18
  Speaker 3: It always spreads out a little bit. You just can't
• 5:20
  Speaker 3: focus it arbitrarily sharply.
• 5:22
  Speaker 2: So there's a minimum size to the spot you can
• 5:24
  Speaker 2: make with light.
• 5:25
  Speaker 3: Yes, And the consequence of that is that conventional optical microscopes,
• 5:30
  Speaker 3: the kind you might remember from high school biology or
• 5:32
  Speaker 3: even the really expensive ones in medical labs. They cannot
• 5:35
  Speaker 3: resolve structures that are smaller than roughly half the wavelength
• 5:39
  Speaker 3: of the light they're using.
• 5:40
  Speaker 2: Okay, so let's put some numbers on this to make
• 5:42
  Speaker 2: it real. Visible light has a wavelength of what somewhere
• 5:45
  Speaker 2: between four hundred and seven hundred animeters roughly. Yeah, that's
• 5:48
  Speaker 2: the range, which means the absolute best resolution you can
• 5:52
  Speaker 2: possibly get with visible light is maybe two hundred animeters.
• 5:57
  Speaker 3: Best case scenario. Yes, and an atom is atom is
• 6:00
  Speaker 3: typically in the range of point one two point three nanometers.
• 6:04
  Speaker 2: Okay, so the scale is completely off. It's not even close.
• 6:07
  Speaker 2: We are trying to pick up a single sesame seed
• 6:10
  Speaker 2: with a bulldozer. The lightweights are literally thousands of times
• 6:14
  Speaker 2: too fat to feel the atom.
• 6:16
  Speaker 3: That is the perfect way to visualize it. And that's why,
• 6:19
  Speaker 3: for the longest time, the very building blocks of matter,
• 6:22
  Speaker 3: the atoms themselves, were simply beyond direct optical observation. We
• 6:26
  Speaker 3: literally could not see them with light.
• 6:28
  Speaker 2: Now, I know what some of our listeners are probably
• 6:29
  Speaker 2: thinking right now, Who cares about light? We have electron microscopes.
• 6:33
  Speaker 2: I've seen those black and like pictures of atoms from
• 6:35
  Speaker 2: electron microscopes. So why is this specific breakthrough with light
• 6:39
  Speaker 2: so important?
• 6:40
  Speaker 3: That is a really critical distinction. And yes, you're right.
• 6:42
  Speaker 3: We do have electron microscopes and scanning tunneling microscopes that
• 6:46
  Speaker 3: use physical probes, and those are amazing, amazing.
• 6:49
  Speaker 2: Tool, but they have limitations.
• 6:51
  Speaker 3: Severe limitations. Electron microscopes, for example, often require a high
• 6:56
  Speaker 3: vacuum that means you can't look at anything that's wet
• 6:59
  Speaker 3: or alive volatile, so no biology, really not living biology. No,
• 7:03
  Speaker 3: And the high energy electrons you use can actually damage
• 7:07
  Speaker 3: or destroy the very sample you're trying to look at.
• 7:10
  Speaker 2: So you get the picture, but you might kill the
• 7:12
  Speaker 2: patient in the process often.
• 7:14
  Speaker 3: Yes, And those physical probes, the scanning ones, are very
• 7:17
  Speaker 3: very slow. They literally drag a needle across a surface
• 7:20
  Speaker 3: line by line.
• 7:21
  Speaker 2: Like an old dot matrix printer, a very.
• 7:24
  Speaker 3: Very slow one.
• 7:24
  Speaker 2: Yes.
• 7:25
  Speaker 3: Light, on the other hand, is fast, it's generally non destructive,
• 7:29
  Speaker 3: and most importantly, light interacts with materials in unique ways
• 7:32
  Speaker 3: that tell us about their chemical and electronic properties. If
• 7:35
  Speaker 3: we could just see atoms with light, we could learn
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  Speaker 3: things that electron microscopes simply cannot tell us.
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  Speaker 2: So the goal has always been this kind of holy grail.
• 7:44
  Speaker 2: Can we get the resolution of an electron microscope but
• 7:47
  Speaker 2: with the versatility and the speed of light.
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  Speaker 3: That has been the dream, and that is exactly what
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  Speaker 3: this team from Regensburg and Birmingham went hunting for.
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  Speaker 2: So let's talk about their setup. They knew they couldn't
• 7:57
  Speaker 2: just use a normal lens because of that diffraction limit
• 7:59
  Speaker 2: we just talked about. So how did they try to
• 8:03
  Speaker 2: cheat the system? What was the work around?
• 8:05
  Speaker 3: Their approach falls under a category of science called near
• 8:08
  Speaker 3: field optics. The basic idea is, if the problem is
• 8:12
  Speaker 3: that lightweights are too big when they're traveling through free
• 8:15
  Speaker 3: space what we call the far field, right, the solution
• 8:18
  Speaker 3: is to manipulate the light right up against the object
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  Speaker 3: you want.
• 8:21
  Speaker 2: To look at, so get up close and personal. You
• 8:23
  Speaker 2: eliminate the travel distance where it can spread out extremely close.
• 8:27
  Speaker 3: They used a setup that involves a very sharp metal tip.
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  Speaker 3: Now when I say sharp, I don't mean like a
• 8:32
  Speaker 3: needle you'd sew with. I mean atomically sharp.
• 8:35
  Speaker 2: Atomically sharp. What does that even mean? In practice?
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  Speaker 3: It means the radius of curvature at the very apex
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  Speaker 3: of this tip is typically about ten nanometers ten animeters.
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  Speaker 2: Okay, for context, a human hair is roughly eighty thousand
• 8:48
  Speaker 2: to one hundred thousand nanometers wide, So this tip is
• 8:52
  Speaker 2: thousands of times sharper than a single hair.
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  Speaker 3: It is, and the technique involves bringing this tip extraordinarily
• 8:58
  Speaker 3: close to the surface of the material they want to study,
• 9:01
  Speaker 3: hovering just above it.
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  Speaker 2: So they have this nanometer sharp needle floating over a sample. Yeah,
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  Speaker 2: then what do they just shine a light on it
• 9:09
  Speaker 2: and hope for the best.
• 9:10
  Speaker 3: Yes, but with a clever twist, they use a continuous
• 9:13
  Speaker 3: wave laser to illuminate the whole system. Now, normally that
• 9:17
  Speaker 3: light would just hit the surface and bounce off, and
• 9:19
  Speaker 3: you'd be stuck with the same.
• 9:20
  Speaker 2: Old diffraction limit, the bulldozer problem again exactly.
• 9:24
  Speaker 3: But because that sharp metal tip is there, something really
• 9:27
  Speaker 3: interesting happens. The system squeezes the infrared light into the
• 9:32
  Speaker 3: tiny gap between the tip and.
• 9:34
  Speaker 2: The sample, squeezing light. I love that image. It sounds
• 9:38
  Speaker 2: like they are physically forcing the light to be smaller
• 9:41
  Speaker 2: than it wants to be, like putting a corset on
• 9:44
  Speaker 2: a photon.
• 9:44
  Speaker 3: That's a fair way to visualize it. It's a phenomenon
• 9:47
  Speaker 3: called plasmonic nanofocusing. The presence of the metal tip acts
• 9:51
  Speaker 3: like a lightning rod or an antenna, and it concentrates
• 9:54
  Speaker 3: the light field right at its apex.
• 9:56
  Speaker 2: So it's a funnel.
• 9:57
  Speaker 3: It's a perfect funnel for light. It confines the energy
• 10:00
  Speaker 3: and by doing this they completely bypass the diffraction limit
• 10:03
  Speaker 3: because the light isn't traveling freely anymore. It's trapped in
• 10:06
  Speaker 3: this tiny, tiny cavity.
• 10:08
  Speaker 2: So by confining the light to the very end of
• 10:10
  Speaker 2: the tip, the resolution of the picture you take is
• 10:14
  Speaker 2: no longer determined by the wavelength of the light, but
• 10:16
  Speaker 2: by the size of the tip exactly.
• 10:18
  Speaker 3: The resolution becomes roughly the size of the tip's apex.
• 10:22
  Speaker 3: In this case that's about ten nanometers, which is huge.
• 10:25
  Speaker 2: Right, I mean, going from two hundred nanometers down to
• 10:27
  Speaker 2: ten ananimeters is a massive jump.
• 10:29
  Speaker 3: Oh, it's a dramatic improvement. This technique, in its early
• 10:32
  Speaker 3: stages is called near field optical tunneling emission, and getting
• 10:36
  Speaker 3: down to ten nanometers is a massive victory for optical microscopy.
• 10:41
  Speaker 3: It allows you to see things like large molecules, proteins,
• 10:43
  Speaker 3: that kind of thing.
• 10:44
  Speaker 2: But and there is always a butt in these stories,
• 10:47
  Speaker 2: isn't there always ten nanometers is still not an atom correct?
• 10:50
  Speaker 3: As we establish, atoms are generally in that zero point
• 10:53
  Speaker 3: one two point three nanometer range. So while ten nanometers
• 10:57
  Speaker 3: is incredibly small, it's still about a factor of three
• 11:00
  Speaker 3: alreaty two coarse to see an individual atom.
• 11:02
  Speaker 2: It's like trying to type on a smartphone keyboard while
• 11:04
  Speaker 2: you're wearing boxing gloves. You know the keys are there,
• 11:08
  Speaker 2: but your finger, or in this case, the tip is
• 11:11
  Speaker 2: just too wide to hit one at a time.
• 11:12
  Speaker 3: That is a perfect analogy. If you scan a grid
• 11:15
  Speaker 3: of atoms with a ten nanimeter wide tip, you are
• 11:18
  Speaker 3: effectively averaging the signal from dozens, maybe hundreds of atoms,
• 11:22
  Speaker 3: all at once. The image you get just looks like
• 11:25
  Speaker 3: a smooth surface. You can't see the individual bumps, you
• 11:28
  Speaker 3: can't see the lattice structure.
• 11:29
  Speaker 2: So up until January thirtieth of this year, the consensus
• 11:33
  Speaker 2: was essentially this is as good as it gets. You
• 11:36
  Speaker 2: can squeeze light down to the size of your tip,
• 11:38
  Speaker 2: but you can't really make the tip smaller than about
• 11:40
  Speaker 2: ten nanimeters because well, metal isn't infinitely strong. You run
• 11:44
  Speaker 2: into physical limits, right.
• 11:45
  Speaker 3: You run into structural limits of the material itself. So
• 11:48
  Speaker 3: they had a great microftote had an amazing microscope, but
• 11:51
  Speaker 3: it wasn't an atomic microscope.
• 11:53
  Speaker 2: And this is where the story gets really good because
• 11:56
  Speaker 2: typically in science, when you hit a physical limit, like
• 11:59
  Speaker 2: the size of your tool, you sort of accept it
• 12:01
  Speaker 2: and work around it. But this team, led by the
• 12:04
  Speaker 2: researchers at the Regensburg Center for Ultra Fastinoscopy, they were
• 12:08
  Speaker 2: determined to find the absolute limit.
• 12:11
  Speaker 3: They wanted to know what happens if you just keep pushing, So.
• 12:13
  Speaker 2: They started moving the tip closer and closer to the
• 12:16
  Speaker 2: surface just to see what would happen to that confined
• 12:19
  Speaker 2: light as the gap got smaller and smaller.
• 12:22
  Speaker 3: Yeah, and we are talking about closing the gap down
• 12:26
  Speaker 3: to atomic dimensions. Here they are hovering a sharp metal spike,
• 12:31
  Speaker 3: maybe a single atom's width away from the surface.
• 12:34
  Speaker 2: That sounds incredibly risky. Yeah, And what happens if you
• 12:37
  Speaker 2: touch the surface? Do you just crash the machine?
• 12:39
  Speaker 3: You absolutely crash the tip, you blunt it, you ruin
• 12:42
  Speaker 3: the sample. The experiments over. It's like trying to fly
• 12:44
  Speaker 3: a helicopter six inches off the ground in the middle
• 12:47
  Speaker 3: of a hurricane. It requires an immense amount of stability
• 12:50
  Speaker 3: and precision, but.
• 12:51
  Speaker 2: They did it. They kept reducing the distance between the
• 12:54
  Speaker 2: tip and the sample until it was comparable to the
• 12:57
  Speaker 2: spacing between individual atoms.
• 13:00
  Speaker 3: This is where the AHA moment happens. I was reading
• 13:03
  Speaker 3: the account from Felix Shiell, one of the lead authors
• 13:06
  Speaker 3: from the University of Regensburg. He described it almost like
• 13:09
  Speaker 3: a shock.
• 13:10
  Speaker 2: Yeah. He noted that at these very very small distances,
• 13:13
  Speaker 2: the signal, the light that was coming back from that
• 13:16
  Speaker 2: tiny gap, it just shot up dramatically. It wasn't a
• 13:20
  Speaker 2: gradual increase, it was a massive spike.
• 13:22
  Speaker 3: And he said, and this is the quote, we didn't
• 13:24
  Speaker 3: immediately understand what was happening. That is the most exciting
• 13:28
  Speaker 3: sentence in all of science. It's never eureka, it's.
• 13:30
  Speaker 2: Huh, that's weird. That's weird. Usually proceeds either a Nobel
• 13:34
  Speaker 2: prize or a laboratory fire, in this case, hopefully the former.
• 13:38
  Speaker 3: Hopefully they realized that when that signal spiked, the resolution
• 13:42
  Speaker 3: of their image suddenly sharpened. I mean drastically.
• 13:44
  Speaker 2: You weren't seeing those ten nanimeter blobs anymore.
• 13:47
  Speaker 3: No, they were suddenly resolving features down to point one nanimeters.
• 13:51
  Speaker 2: Zero point one nanometers, that is the atomic scale. They
• 13:54
  Speaker 2: were suddenly seeing the atoms they were.
• 13:56
  Speaker 3: They had inadvertently accidentally broken the barrier. But the question,
• 14:00
  Speaker 3: of course, was how their tip was still ten nanometers wide.
• 14:05
  Speaker 3: How could a ten nanometer tip possibly take a zero
• 14:07
  Speaker 3: point one nanometer picture?
• 14:09
  Speaker 1: Right?
• 14:10
  Speaker 2: I mean, let's go back to our boxing glove analogy. Yeah,
• 14:12
  Speaker 2: how did the boxing gloves suddenly turn into a needle.
• 14:14
  Speaker 2: The glove didn't.
• 14:15
  Speaker 3: Change size, the glove didn't change, but the physics of
• 14:18
  Speaker 3: the interaction changed. And this is why we're here today.
• 14:21
  Speaker 3: The answer lies in quantum mechanics.
• 14:24
  Speaker 2: Okay, let's unpack this. This is where we need to
• 14:26
  Speaker 2: be really careful, because quantum mechanics is usually where our
• 14:29
  Speaker 2: everyday intuition goes to die. How does a quantum effect
• 14:32
  Speaker 2: turn a ten nanometer flashlight into an atomic spotlight?
• 14:36
  Speaker 3: It all has to do with what happens in that tiny,
• 14:39
  Speaker 3: tiny gap between the tip and the sample. Now, in
• 14:41
  Speaker 3: the classical world, the world of baseballs and planets, if
• 14:44
  Speaker 3: you hold a ball close to a wall, but you
• 14:46
  Speaker 3: don't touch it, the ball stays in your hand, there
• 14:49
  Speaker 3: is a gap. Nothing closses it.
• 14:50
  Speaker 2: Right, almost touching is still not touching, the circuit is open,
• 14:54
  Speaker 2: no electricity flows.
• 14:55
  Speaker 3: But in the quantum world, things are well, they're fuzzier.
• 15:00
  Speaker 3: Electrons Specifically, they have a probability of being in different
• 15:03
  Speaker 3: places at once. They aren't just hard little marbles. They
• 15:06
  Speaker 3: are more like probability clouds. Okay, And if you bring
• 15:10
  Speaker 3: two conductive materials close enough together, like the metal tip
• 15:13
  Speaker 3: and the sample surface, the edge of the electron cloud
• 15:16
  Speaker 3: in the tip starts to actually overlap with the sample.
• 15:19
  Speaker 2: So even though there is still empty space between them, physically,
• 15:23
  Speaker 2: the electron can sort of bridge that gap.
• 15:26
  Speaker 3: Exactly, there is a non zero probability that an electron
• 15:30
  Speaker 3: can simply appear on the other side. It doesn't travel
• 15:33
  Speaker 3: through the space, It tunnels through the barrier of empty space.
• 15:36
  Speaker 3: It's a purely quantum effect.
• 15:38
  Speaker 2: Okay, so we have electrons tunneling. I've heard of scanning
• 15:40
  Speaker 2: tunneling microscopes, so that part makes sense. But tunneling usually
• 15:44
  Speaker 2: just creates an electrical current. How does that create light?
• 15:47
  Speaker 2: And more importantly, how does it create this super resolution light.
• 15:51
  Speaker 3: This is where the laser comes back into play. Remember
• 15:53
  Speaker 3: they are constantly shining that infrared laser on the whole system.
• 15:56
  Speaker 3: Light is an electromagnetic wave. That means it consists of
• 15:59
  Speaker 3: an an oscillating electric field. It pushes and it pulls
• 16:03
  Speaker 3: on charged particles like electrons.
• 16:06
  Speaker 2: So the light is providing this rhythmic push pull push pull.
• 16:09
  Speaker 3: Correct, This infrared light creates a continuously oscillating electric field
• 16:15
  Speaker 3: right in that tiny gap, and it acts as a driver.
• 16:18
  Speaker 3: This field forces the electrons to leap back and forth
• 16:21
  Speaker 3: between the apex atom of the tip and the sample.
• 16:24
  Speaker 2: So the light is like a pump or maybe a
• 16:26
  Speaker 2: conductor's baton, setting the rhythm it.
• 16:28
  Speaker 3: Conductor's baton is a great way to think of it.
• 16:30
  Speaker 3: It drives the rhythm. The electrons are tunneling back and forth,
• 16:33
  Speaker 3: but they're doing it in perfect time with the frequency
• 16:35
  Speaker 3: of the laser light.
• 16:36
  Speaker 2: Okay, so we have electrons jumping back and forth across
• 16:39
  Speaker 2: this gap in time with the laser. I'm still missing
• 16:42
  Speaker 2: the last step. How does that help us see anything.
• 16:45
  Speaker 3: This is where the antenna analogy they use in the
• 16:46
  Speaker 3: paper comes in, and it's perfect. Think about how a
• 16:49
  Speaker 3: simple radio antenna works. You drive electrons up and down
• 16:52
  Speaker 3: a metal rod with an electrical signal, and that acceleration
• 16:55
  Speaker 3: of electrons generates radio waves, it generates an electromagnetic signal.
• 17:00
  Speaker 2: Moving electrons create electromagnetic waves. That's physics, one.
• 17:03
  Speaker 3: On one right exactly now, in this experiment, the electrons
• 17:07
  Speaker 3: that are tunneling back and forth between the tip and
• 17:09
  Speaker 3: the sample, they're doing the exact same thing. They are
• 17:13
  Speaker 3: acting like a tiny, single atom sized antenna, and their
• 17:18
  Speaker 3: motion produces its own faint electromagnetic signal, a little pulse
• 17:22
  Speaker 3: of light.
• 17:22
  Speaker 2: Essentially, wait a second, stop, this is the part that
• 17:24
  Speaker 2: I want to make absolutely sure I'm getting the light
• 17:27
  Speaker 2: that they are detecting. It isn't the laser light bouncing
• 17:30
  Speaker 2: off the atom.
• 17:31
  Speaker 3: No, and that is the absolute critical distinction. The light
• 17:35
  Speaker 3: they detect is what they call the near field optical
• 17:38
  Speaker 3: tunneling emission. It is light that is generated by the
• 17:41
  Speaker 3: electrons motion as it tunnels back and forth.
• 17:43
  Speaker 2: That is mind blowing. So the laser isn't the illumination
• 17:46
  Speaker 2: the lasers the engine. The electron itself is the light bulb.
• 17:49
  Speaker 3: That is a beautiful way to put it. The laser
• 17:51
  Speaker 3: drives the electron, and the electron then broadcasts its own
• 17:54
  Speaker 3: position by emitting light.
• 17:56
  Speaker 2: Okay, okay, but why does this solve the fat finger problem?
• 18:00
  Speaker 2: The boxing glove problem. Why is the resolution so unbelievably.
• 18:04
  Speaker 3: Good Because quantum tunneling is incredibly sensitive to distance, I
• 18:08
  Speaker 3: mean exponentially sensitive. If you move the tip just a
• 18:11
  Speaker 3: tiny tiny bit further away, even just half an atom's
• 18:14
  Speaker 3: with the probability of an electron tunneling drops to almost zero.
• 18:18
  Speaker 3: It just stops.
• 18:19
  Speaker 2: So the tunneling only happens at the absolute closest point
• 18:22
  Speaker 2: between a tip and the sample.
• 18:24
  Speaker 3: Yes, think about the geometry of the tip. It's a curve, right, Yeah,
• 18:27
  Speaker 3: even though the metal tip is ten nanimeters wide. Overall,
• 18:31
  Speaker 3: the only place that is close enough to the sample
• 18:33
  Speaker 3: to allow tunneling is the single atom at the very
• 18:36
  Speaker 3: very apex of that curve. The atoms right next to
• 18:39
  Speaker 3: it on the tip are just slightly further away, and
• 18:41
  Speaker 3: for tunneling, slightly is everything.
• 18:44
  Speaker 2: So the active part of the sensor effectively shrinks from
• 18:46
  Speaker 2: the whole ten nanimeter tip down to just that one
• 18:49
  Speaker 2: final atom.
• 18:50
  Speaker 3: At the point precisely. The rest of the tip is silent,
• 18:53
  Speaker 3: it's too far away. Only that one single atom is
• 18:56
  Speaker 3: broadcasting the signal. Yeah, that is how they get point
• 18:59
  Speaker 3: one nimes resolution from a ten nanimeter object.
• 19:01
  Speaker 2: That is just it's incredibly clever. You're using the geometry
• 19:04
  Speaker 2: and the rules of quantum probability to filter out everything
• 19:08
  Speaker 2: except the signal from a single point.
• 19:10
  Speaker 3: It creates a virtual probe that is much much smaller
• 19:13
  Speaker 3: than the physical probe you're using.
• 19:15
  Speaker 2: There was a stat in the research that just completely
• 19:17
  Speaker 2: floored me. Doctor Tom Saiday from the University of Birmingham.
• 19:21
  Speaker 2: He was trying to explain the sensitivity of this measurement.
• 19:24
  Speaker 2: He said, and I'm quoting here, just one electron moving
• 19:27
  Speaker 2: over a distance smaller than the size of an atom
• 19:29
  Speaker 2: every hundred cycles of the.
• 19:31
  Speaker 3: Light can already produce light that is strong enough for
• 19:33
  Speaker 3: us to detect.
• 19:34
  Speaker 2: That is absurd. One electron every hundred times the light
• 19:40
  Speaker 2: wave oscillates. I mean, we talk about precision measurement, but
• 19:44
  Speaker 2: that sounds like it's straight out of science fiction.
• 19:46
  Speaker 3: It really highlights just how powerful this technique is. We're
• 19:49
  Speaker 3: not blasting the sample with high energy to get a signal.
• 19:53
  Speaker 3: We are tuning in and listening to the electromagnetic whisper
• 19:56
  Speaker 3: of a single particle doing its quantum dance.
• 20:00
  Speaker 2: What does this all mean for what we are actually seeing.
• 20:02
  Speaker 2: You mentioned earlier that we aren't taking a picture in
• 20:05
  Speaker 2: the traditional sense. If I look at the data coming
• 20:07
  Speaker 2: out of this machine, am I seeing a photograph of
• 20:10
  Speaker 2: a bunch of atoms?
• 20:11
  Speaker 3: Not exactly a photograph. No. Valentin Berkbauer from the University
• 20:15
  Speaker 3: of Regensburg, he put it really well. He said, we
• 20:17
  Speaker 3: are no longer limited by how tightly light can be confined. Instead,
• 20:21
  Speaker 3: what we're doing is directly controlling and measuring quantum electron motion.
• 20:26
  Speaker 2: Okay, so translate that for me. If I'm looking at
• 20:28
  Speaker 2: the screen, what is the image that I'm seeing actually
• 20:31
  Speaker 2: telling me?
• 20:31
  Speaker 3: You are seeing a map, But it's a map of
• 20:33
  Speaker 3: probability and conductivity because the signal you detect depends entirely
• 20:38
  Speaker 3: on electrons being able to tunnel. It tells you how
• 20:41
  Speaker 3: easy it is for electrons to move at that specific
• 20:45
  Speaker 3: point in the material.
• 20:46
  Speaker 2: So it's a map of how well electricity flows. But
• 20:49
  Speaker 2: at the level of a single atom.
• 20:50
  Speaker 3: Yes, you are measuring the materials local conductivity with atomic
• 20:54
  Speaker 3: scale precision, and that is incredibly valuable information because conductivity
• 20:59
  Speaker 3: isn't always uniform, especially in advanced materials. You might have
• 21:03
  Speaker 3: defects or impurities, or specific atomic arrangements that conduct better
• 21:06
  Speaker 3: or worse than the atoms next to them. This tool
• 21:09
  Speaker 3: lets you see those variations atom by atom.
• 21:12
  Speaker 2: The paper says this pushes optical microscopy to length scales
• 21:17
  Speaker 2: nearly one hundred thousand times smaller than conventional light based microscopes.
• 21:22
  Speaker 2: That number is just staggering to even think about.
• 21:25
  Speaker 3: It completely redefines the field. We are moving from simply
• 21:29
  Speaker 3: observing the shape of things to observing the behavior of
• 21:32
  Speaker 3: things at the most fundamental quantum level.
• 21:35
  Speaker 2: Now here's where it gets really interesting for the people
• 21:37
  Speaker 2: listening who might work in labs or follow technology trends.
• 21:41
  Speaker 2: Usually when we hear about a breakthrough like this atomic
• 21:43
  Speaker 2: resolution quantum tunneling, my brain immediately goes to one place. Okay,
• 21:48
  Speaker 2: that sounds expensive. I'm imagining a machine the size of
• 21:51
  Speaker 2: a room that costs fifty million dollars and requires a
• 21:55
  Speaker 2: team of twelve PhDs just to turn on.
• 21:57
  Speaker 3: That is the standard assumption. And you know, usually you
• 22:00
  Speaker 3: would be absolutely right. In the past you get anywhere
• 22:02
  Speaker 3: near this kind of temporal or spatial resolution, you needed
• 22:05
  Speaker 3: what are called ultrafast lasers, right, and these are incredibly complex, finicky,
• 22:09
  Speaker 3: and very very expensive pieces of equipment that produce ultra
• 22:12
  Speaker 3: short pulses of light pulses that last only for femtoseconds, and.
• 22:16
  Speaker 2: A femtosecond is a quadrillianth of a.
• 22:18
  Speaker 3: Second quadrilliant of a second. Yes, and maintaining a laser
• 22:22
  Speaker 3: that can do that consistently is a nightmare. It's like
• 22:25
  Speaker 3: owning a Formula one car. It's incredibly fast, but it
• 22:29
  Speaker 3: spends half its life in the garage being tuned by specialists.
• 22:32
  Speaker 2: But I feel a butt coming.
• 22:34
  Speaker 3: But this team did it all with a standard continuous
• 22:37
  Speaker 3: wave laser.
• 22:38
  Speaker 2: Standard as in as in.
• 22:40
  Speaker 3: The kind of laser technology that is widespread, robust, and
• 22:43
  Speaker 3: relatively affordable. A continuous wave laser just emits a steady,
• 22:48
  Speaker 3: constant beam of light. It's not pulsing at femt too
• 22:51
  Speaker 3: second speeds. It's simple.
• 22:53
  Speaker 2: Why is that such a big deal? I mean, apart
• 22:55
  Speaker 2: from just saving money on the initial purchase.
• 22:57
  Speaker 3: It democratizes the science. It's all about accessibility. If you
• 23:01
  Speaker 3: need a five million dollar laser setup to do this
• 23:04
  Speaker 3: kind of work, then only a handful of elite labs
• 23:06
  Speaker 3: in the world can ever verify your results or use
• 23:09
  Speaker 3: the technique to discover new things.
• 23:11
  Speaker 2: But if you can do it with a standard laser setup.
• 23:13
  Speaker 3: Suddenly, thousands of labs around the world can potentially implement this.
• 23:17
  Speaker 3: It dramatically lowers the barrier to.
• 23:19
  Speaker 2: Entry, which accelerates the rate of discovery across the board exactly.
• 23:23
  Speaker 3: The simplicity of this setup I mean simplicity is relative.
• 23:27
  Speaker 3: Of course, we're still talking about very advanced optics. But
• 23:29
  Speaker 3: that relative simplicity means this technique could become a standard
• 23:33
  Speaker 3: tool in material science much much faster than if it
• 23:37
  Speaker 3: required exotic, expensive gear.
• 23:39
  Speaker 2: So we might see this popping up in university labs,
• 23:42
  Speaker 2: in corporate R and D centers much sooner than we'd think.
• 23:45
  Speaker 3: That is absolutely the hope. The researchers themselves explicitly mentioned
• 23:49
  Speaker 3: that this simplicity could help make the technique more widely accessible.
• 23:54
  Speaker 3: It's the difference between a tool that only exists at
• 23:56
  Speaker 3: a place like CERN and a tool that can exist
• 23:59
  Speaker 3: at every research university.
• 24:01
  Speaker 2: I want to zoom out a bit now. Pun definitely intended.
• 24:04
  Speaker 2: We've talked about the how and the what. Let's really
• 24:07
  Speaker 2: dig into the why. Why do we need to see
• 24:10
  Speaker 2: atoms this? Clearly? What does this unlock for the future.
• 24:13
  Speaker 3: The source material touches on this, and I think it's
• 24:15
  Speaker 3: the most exciting part. It's all about the connection between
• 24:17
  Speaker 3: the micro and the macro.
• 24:18
  Speaker 2: Okay, connect those dots for me. What does that mean?
• 24:21
  Speaker 3: Think about any advanced material you use every day. The
• 24:24
  Speaker 3: screen on your phone, the battery in your electric car,
• 24:27
  Speaker 3: the solar panel on your roof. All of these things
• 24:29
  Speaker 3: have what we call macroscopic properties.
• 24:32
  Speaker 2: Right, the screen is tough but transparent, The battery holds
• 24:35
  Speaker 2: a charge efficiently, the solar panel absorbs sunlight. Well, those
• 24:39
  Speaker 2: are the things we actually experience. It's the user interface.
• 24:42
  Speaker 3: Of reality exactly. But every single one of those macroscopic
• 24:46
  Speaker 3: properties is determined entirely by what's happening at the microscopic scale,
• 24:51
  Speaker 3: specifically how the atoms are arranged and how they interact
• 24:54
  Speaker 3: with each other and with light.
• 24:56
  Speaker 2: So if a solar panel isn't as efficient as.
• 24:58
  Speaker 3: It could be, often because of something going wrong at
• 25:01
  Speaker 3: the atomic level, Right at the moment where the photon
• 25:04
  Speaker 3: hits the material and is supposed to create an electron
• 25:06
  Speaker 3: hole pair. Maybe the electron gets stuck at a defect
• 25:10
  Speaker 3: in the crystal lattice, Maybe it recombines too quickly and
• 25:12
  Speaker 3: the energy is lost as heat.
• 25:15
  Speaker 2: So if we want to build better, more efficient solar panels.
• 25:18
  Speaker 2: We need to be able to see exactly what's going
• 25:20
  Speaker 2: wrong or what's going right at that single atom level precisely.
• 25:25
  Speaker 3: This new approach allows scientists to study how materials interact
• 25:29
  Speaker 3: with light at the scale of individual atoms. We can
• 25:32
  Speaker 3: finally see the quantum machinery that drives the everyday world
• 25:35
  Speaker 3: we live in.
• 25:35
  Speaker 2: It's like trying to fix a car engine. Before we
• 25:39
  Speaker 2: could only look at the engine block from ten feet
• 25:41
  Speaker 2: away and listen to it. Now we can basically open
• 25:43
  Speaker 2: it up, stick our head inside the cylinder and watch
• 25:46
  Speaker 2: the individual valves moving.
• 25:48
  Speaker 3: And not just look at them. We can see how
• 25:50
  Speaker 3: they're moving in real time. We can measure the dynamics.
• 25:53
  Speaker 3: This is why the center in Reagansbird is called this
• 25:55
  Speaker 3: Center for Ultrafast Nanoscopy. It's not a still phototures the action.
• 26:01
  Speaker 2: How does do that well?
• 26:02
  Speaker 3: Because the electron tunneling is being driven by the cycles
• 26:05
  Speaker 3: of the laser light, the time resolution of the measurement
• 26:08
  Speaker 3: is incredibly high, on the order of femtoseconds, So.
• 26:11
  Speaker 2: We can actually make movies of electrons moving.
• 26:14
  Speaker 3: In a sense, yes, we can capture the dynamics of
• 26:16
  Speaker 3: how electrons move through a crystal lattice. How they respond
• 26:19
  Speaker 3: to light with an unbelievable combination of spatial and temporal resolution.
• 26:24
  Speaker 2: That's just wild. I also want to give a shout
• 26:26
  Speaker 2: out here to the human element. This wasn't some solo
• 26:28
  Speaker 2: genius toiling away in a basement. This was a deep
• 26:31
  Speaker 2: collaboration between the University of Regensburg in Germany and the
• 26:35
  Speaker 2: University of Birmingham in the UK.
• 26:36
  Speaker 3: Oh. Absolutely, science at this level is increasingly a team sport.
• 26:40
  Speaker 3: You had the experimental expertise in Regensburg, the people who
• 26:44
  Speaker 3: physically build the setup, create the tip, align the lasers,
• 26:49
  Speaker 3: and you had the crucial theoretical contributions from Birmingham, people
• 26:53
  Speaker 3: like doctor Tom Saide, Felix Schiegel, Valentin Bergbauer. It really
• 26:57
  Speaker 3: does take a village to see.
• 26:58
  Speaker 2: An adam, It really does. And I have to mend
• 27:00
  Speaker 2: the visual they released with the paper. I know this
• 27:02
  Speaker 2: is an audio format, but the artistic representation they had,
• 27:05
  Speaker 2: done by an artist named Brad Baxley, is so cool.
• 27:08
  Speaker 2: It shows these bright glowing spheres, the electrons leaping back
• 27:11
  Speaker 2: and forth between the sharp point of the tip and
• 27:14
  Speaker 2: the flat sample below. It really drives home that we
• 27:17
  Speaker 2: aren't looking at static rocks anymore, We're looking at a dynamic,
• 27:20
  Speaker 2: buzzing gants of quantum particles.
• 27:23
  Speaker 3: It helps visualize the invisible, and that is really the
• 27:27
  Speaker 3: core of what this discovery is all about. It changes
• 27:29
  Speaker 3: our fundamental mental model of the material world.
• 27:32
  Speaker 2: Okay, so let's try to recap the journey we've been
• 27:35
  Speaker 2: on today. This has been a dense one, but I
• 27:38
  Speaker 2: think the payoff is absolutely huge.
• 27:40
  Speaker 3: We started with the diffraction limit, this old idea that
• 27:43
  Speaker 3: light waves are just too big and clumsy to see
• 27:45
  Speaker 3: something as small as an atom, a fundamental wall of
• 27:48
  Speaker 3: physics that stood for centuries.
• 27:50
  Speaker 2: Then we introduced the heroes of our story, the team
• 27:53
  Speaker 2: from Regensburg and Birmingham, who decided to cheat. They decided
• 27:56
  Speaker 2: to squeeze light into a tiny gap beneath the sharp
• 28:00
  Speaker 2: metal tip, using this idea of near field optics.
• 28:03
  Speaker 3: And they kept pushing that tip closer to the absolute
• 28:05
  Speaker 3: limit until the classical world gave way and the quantum
• 28:08
  Speaker 3: world took.
• 28:09
  Speaker 2: Over, which led to that complete surprise that that's weird moment.
• 28:12
  Speaker 2: Quantum tunneling allowed them to use a simple standard laser
• 28:15
  Speaker 2: to drive electrons back and forth, effectively turning a single
• 28:18
  Speaker 2: atom into a broadcast antenna.
• 28:20
  Speaker 3: Resulting in an unbelievable zero point one nanometer resolution, true
• 28:25
  Speaker 3: atomic vision, and a way to measure a material's conductivity
• 28:28
  Speaker 3: with a precision we've never had before.
• 28:30
  Speaker 2: And maybe most importantly for the future of science, they
• 28:33
  Speaker 2: did it all with equipment that is surprisingly accessible, which
• 28:37
  Speaker 2: opens the door for a revolution in how we study
• 28:41
  Speaker 2: and design new materials.
• 28:43
  Speaker 3: It's a classic scientific story. Really, you hit a wall,
• 28:45
  Speaker 3: so you figure out how to dig a tunnel under it,
• 28:48
  Speaker 3: in this case literally a quantum tunnel.
• 28:50
  Speaker 2: I love that, and I really liked the phrase they
• 28:52
  Speaker 2: used in their paper to describe it, atomic scale telegraphy
• 28:56
  Speaker 2: with light.
• 28:57
  Speaker 3: It fits perfectly, doesn't it. We are literally tapping out
• 29:00
  Speaker 3: messages using single electrons as the messengers, dot dash dot.
• 29:04
  Speaker 2: It really forces you to reconsider what we even mean
• 29:07
  Speaker 2: when we say fundamental limitations.
• 29:09
  Speaker 3: It does. It's a good reminder that fundamental often just
• 29:12
  Speaker 3: means we haven't figured out the cleve workaround yet.
• 29:15
  Speaker 2: And that's really where I want to leave our listeners today.
• 29:18
  Speaker 2: We all grow up learning these hard and fast rules.
• 29:20
  Speaker 2: You can't go faster than light, you can't see atoms
• 29:23
  Speaker 2: with light, you can't be in two places at once,
• 29:25
  Speaker 2: and yet.
• 29:26
  Speaker 3: Quantum mechanics seems to view these rules more as suggestions,
• 29:31
  Speaker 3: or at the very least as puzzles to be solved
• 29:33
  Speaker 3: in interesting ways.
• 29:34
  Speaker 2: Exactly, we just learned how we used light something huge
• 29:38
  Speaker 2: in wave like to prod single electrons, and that those
• 29:42
  Speaker 2: electrons shatted back loud enough for us to hear them.
• 29:45
  Speaker 2: It just makes you wonder what other impossible barriers are
• 29:48
  Speaker 2: just sitting there, waiting for the right trick to write,
• 29:52
  Speaker 2: atomically sharp tip, or the right happy accident to be
• 29:55
  Speaker 2: broken wide open.
• 29:56
  Speaker 3: Perhaps the limit isn't in the physics at all, but
• 29:58
  Speaker 3: just in our imagination of how to.
• 29:59
  Speaker 2: Apply a profound thought to end on. Thanks for exploring
• 30:03
  Speaker 2: this breakthrough with us, Keep questioning the limit, and keep
• 30:05
  Speaker 2: looking closer. See you next time.