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

to create superconductivity.

It's an incredible challenge to try and find

a new material that's a superconductor.

So in thinking about how to create new superconductors,

it was almost a question of looking at a scrambled Rubik's

cube and looking at all these elements and trying to think,

how do I put them together into this compound

that superconducts?

And this is challenging.

We don't even understand existing superconductors.

We don't have a pattern, a template

for how to put these elements together

to get a better superconductor, or even

another new superconductor.

But then looking at the existing high temperature

superconductors and similar, other superconductors,

it struck me that actually, there

are patterns to these materials that

may be incredibly helpful in developing

a new superconducting material.

And so possibly, what we could do

is utilize the fact that these materials that

are superconductors were almost magnets, or almost insulators,

or almost charge ordered materials.

And what this might help us do is

start with a material that's a magnet or a charge ordered

material, or an insulator.

These are in abundance, right?

We don't have superconductors in abundance,

but we do have magnets and insulators in abundance.

So what if we took that as a starting point

and anticipate it's very close to being a superconductor.

So let me apply a little force to it

and see if it becomes a superconductor.

This could be an amazing, directed way

to make superconductors instead of this hoping for a random act

to create a superconductor.

This could be a directed way in which

to create new superconductors.

And this was also especially appealing to me

because I am familiar with technologies

to apply these large forces on materials.

This is me working with a giant magnet.

Other ways are to apply large pressures,

to apply large electric fields.

So I thought, OK, let's start with picking a material.

Apply force to it.

So for criteria to pick a material,

I looked at existing superconductors

and what these materials had in common.

And one of the criteria was that it

seemed that these materials weren't dense, three

dimensional materials, but they seem

to be layered or stretched in one direction.

Another criteria, as I briefly mentioned,

these materials seem to be almost magnets.

So they have strong magnetic interactions--

and these are represented by the yellow streaks

on here-- or strong charge interactions.

And a final criteria was that what

we found so counterintuitive, that starting with materials

that are poor metals, or insulators,

this may be an excellent starting point.

So based on these criteria, I picked a material, iron

arsenide.

So this is a magnet.

And it's actually a poor metal.

So it has a high resistance to the flow of electricity.

So I started with this material.

And the blue region on here shows

you the starting magnetism of this material.

So the vertical axis is temperature,

and the horizontal axis is the amount of pressure

I applied to it.

So I synthesized single crystals of this iron arsenide

and then placed a small crystal between the tips of a diamond

anvil cell.

So this is a type of contraption that applies pressure,

and quite high pressures that reach sizes similar to