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  • SUCHITRA SEBASTIAN: So today, I'm

  • going to talk to you about the power of new materials

  • discovery, specifically with respect

  • to a category of materials known as superconductors which

  • have the potential to transform the energy landscape.

  • So this is a picture of the night sky.

  • And the bright regions you see on here

  • are where energy consumption is maximum.

  • You can see this is concentrated in urban areas,

  • whereas energy actually needs to be transported

  • from over the entire globe just to reach these areas.

  • So energy transportation is a big issue.

  • And let's talk about electricity in particular,

  • because we know this is going to grow

  • as a fraction of the total energy consumed.

  • And renewables are an excellent source of electricity.

  • But it turns out that renewables are

  • located at remote locations which

  • are at the opposite ends of the globe

  • from where urban areas of consumption are.

  • So looking forward, electricity infrastructure

  • is going to change.

  • And it's going to be dominated by issues of transport

  • and issues of storage.

  • We need to transport electricity now thousands

  • of miles instead of hundreds of miles.

  • And we need to store this electricity,

  • because where renewable sources are peaked-- for example, when

  • the sun shines the strongest or when the wind blows

  • the hardest-- this is not the same time

  • when demand is peaked.

  • So to be able to match supply and demand

  • needs energy to be stored.

  • Now, these two, electricity transportation and storage,

  • these are just a couple of the applications

  • of this exciting family of materials

  • known as superconductors.

  • So these materials transport electricity without any loss.

  • So if you took a ring made of superconducting wire

  • and sent current through it, it would

  • flow for the age of the universe.

  • So if we go back one-- excellent.

  • Thank you.

  • And so the image on the left shows a prototype

  • of a superconducting cable that's

  • to be used in Germany that's going to be a kilometer long,

  • and it's going to be underground and transport power.

  • And so superconducting cables have natural applications

  • in power transmission given there's zero loss, particularly

  • for long distances, for dense urban areas,

  • for underground transport.

  • And DC technology in particular is making these now viable.

  • The picture you see on the right is perhaps

  • one of the best known examples of a giant superconducting

  • magnet.

  • And this is one of the other applications, superconducting

  • magnets, which are extremely useful.

  • And for instance, to store energy,

  • you can convert electricity into magnetic energy

  • and back again losslessly.

  • You can also use superconducting magnets

  • for gearless and motors, for example, in wind turbines.

  • And probably, you've already come

  • across superconducting magnets.

  • If you've had an MRI done, this is

  • based on superconducting magnets.

  • And now we're going to do the much talked about cool demo.

  • So I'm going to show you a superconductor in action.

  • So what you see here is a track made of magnetic material.

  • So they're rails made of magnetic material.

  • And what I'm going to demonstrate to you

  • is one is the amazing quantum properties of superconductors

  • that make them not only conduct electricity with no loss

  • but also repel magnetic fields.

  • So what I have here is a puck of superconducting material.

  • And so I'm going to position this over the rail.

  • So you can see it levitate.

  • And actually, it started going without my doing anything.

  • So you can see it levitate over the track.

  • OK?

  • Excellent.

  • Now, we're going to try something else.

  • What we're going to try to do is also turn the rail upside down

  • and try to levitate a superconductor

  • underneath the rail, which would be even cooler.

  • So what I'm going to now do is take a very similar

  • superconducting puck and position it now under the rail.

  • Yeah.

  • Levitating underneath.

  • You can see it fly without any dissipation,

  • except for primarily air friction, underneath the rail.

  • So what this is due to is because of persistent currents

  • being set up on the surface of the superconductor that

  • expel magnetic fields.

  • And so this is one of the most dramatic consequences

  • of superconductivity.

  • So I've shown you.

  • You've seen superconductors work.

  • And I told you about all their amazing applications.

  • So a question you might, indeed, ask

  • is, why aren't superconductors everywhere?

  • Why don't we see them much more in everyday life?

  • Why aren't power transmission cables already made out

  • of superconductors?

  • One of the reasons is that these materials only

  • superconduct below a certain superconducting temperature.

  • And so if you notice, one of the pieces of kit I

  • have here is a bucket with liquid nitrogen in it, which

  • I needed to cool the superconductor in for it

  • to work.

  • So in order for these materials to become more applicable,

  • it would be excellent if we had a material that

  • was able to super conduct at a higher temperature.

  • So we'd like to be able to find such higher temperature

  • superconductors.

  • So I got really excited by the prospect

  • of working with superconductors.

  • Who wouldn't like to do this as a day job?

  • So I started trying to understand superconductors.

  • And it turns out that this intricate quantum

  • dance that the electrons do to create superconductivity,

  • especially in these best known superconductors,

  • the ones with the highest superconducting temperature,

  • are actually not understood.

  • So we don't understand why these materials superconduct

  • at such high temperatures.

  • One of the mysterious things we don't understand

  • is this material I showed you that's superconducting

  • is almost an insulator.

  • Now, when I say insulator, you think of paper,

  • of wood, materials that don't carry electricity,

  • forget perfect conductors.

  • So this is just one of the many mysteries

  • of why these materials that are almost insulators

  • are perfect conductors instead.

  • And so there's many mysteries we don't understand

  • about these superconductors.

  • And it's tremendously exciting to work on these cool materials

  • and try to understand them.

  • But it also occurred to me at that point

  • that even if I understood how these materials work, which

  • is really important, would that enable

  • me to make a new superconductor out of a new material?

  • Actually, no.

  • To discover a new material that's a good superconductor,

  • this requires a different kind of thinking.

  • I need to be able to think in terms of relating materials

  • to superconductivity.

  • This becomes a materials question.

  • So then I started thinking about,

  • how am I going to find a new material

  • to make it a superconductor?

  • And I thought about, historically,

  • how have superconductors been found?

  • So the vertical axis on here is superconducting temperature.

  • And the horizontal axis is the year in which they were found.

  • So the early superconductors were discovered 100 years ago.

  • And these had low superconducting temperatures.

  • And it was only about 20 years ago

  • that there was a breakthrough, and materials

  • which superconducted above liquid nitrogen temperatures,

  • like the one I showed you just here, were discovered.

  • And this was a great breakthrough.

  • But if you look at this graph, it looks quite random.

  • And the reason for this is all of these materials

  • were discovered serendipitously.

  • By a happy accident, someone was working on something else

  • and then happened to discover that one of these materials

  • superconducted.

  • And this is great.

  • It's nice that this happened.

  • But it's not a good way forward.

  • It's not a directed way in which we

  • can find better superconductors.

  • And so it's an incredible challenge

  • given that these electrons and superconductors need

  • to behave as a quantum collective