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
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
near the Earth's core, where actually, new materials are
created.
And so I took this material, put a crystal between the tips
of a diamond anvil cell, started pressing on it.
And you can see the temperature go down.
So this is the magnetic temperature.
So the magnetic temperature going down
means it's becoming less and less good
a magnet, which is promising.
But then, at about 5% of a compression
in volume of the crystal lattice,
it transformed into a new superconductor,
which is amazing.
We started with a magnet that was an insulator.
We applied pressure on it.
And it dramatically transformed into a superconductor.
This is almost a form of quantum alchemy.
And this is just the tip of the iceberg.
We've started with materials that are not superconductors,
changed them into a superconductor.
And we know that materials are plentiful.
We have a limitless array of materials
which we can transform into superconductors.
We just need to use the right criteria to pick them,
use large forces on them, and we'll
have an entire array, an explosion
of new superconductors where before, we
had one and two examples.
So we're looking at a materials landscape.
These are just two of the new examples of materials which
I'm working on to transform into superconductors
with promising results.
So what we're looking at is a materials landscape.
We're populating this with new superconductors
with the aim of getting to the summit of a higher temperature
superconductor.
But along the way, we're creating many superconductors
which will give us this ability to optimize materials to create
this ultimate high temperatures superconductor.
And this will have a transformative impact
on everyday life.
So what we're witnessing here is just
the dawn of a new materials era.
And it's going to lead to a revolution which
will surpass even the Industrial Revolution.
Thank you.