So a superconductor is a material which conducts electricity perfectly without any resistance it
also perfectly banishes magnetic fields, so that no magnetic field can penetrate into a
superconductor. There are quite a few applications for them - so some that already exist are they're
used in all MRI scanners in hospitals, magnetic resonance imaging, they're used generally to build
very powerful magnets so they're used for example for magnetic levitation of trains above tracks -
the fastest train in the world at the moment is in Japan and it uses this technology. They're also
used for example to accelerate particles near the speed of light in CERN. So the big problem with
them is that uh the the cases we understand only work at very low temperatures - roughly below 40
degrees Centigrade above absolute zero so much much colder than room temperature. So that's
kind of holding back additional applications the highest temperature superconductors we know of uh
become superconducting only a little bit above the boiling point of liquid nitrogen. So they
do have applications already but they would have many more applications if we could get them up to
room temperature for example we could use them in power lines and and other uses where we'd need to
conduct electricity without any resistance. So the thing about conducting electricity without
resistance that is so useful is that for example to take a kind of wild idea you could imagine
covering the Sahara in solar panels and sending the electricity out all around the world - without
losing any along the way. With current technology if we use normal metals to conduct electricity we
necessarily lose a lot of it on the way in fact I calculated that in the United States
alone every year the amount of energy that's lost in transmitting the electricity from where
it's generated to where it's used, would be enough to power the street lights of Manhattan
for a thousand years. So that's every year that amount of energy is lost. So the low temperature
superconductors we understand incredibly well I'd say it's probably one of our best theories
in all of physics. So they were first discovered in 1911 and in 1956 I think it was the theory of
how they worked was explained by Barden, Cooper and Schrieffer - so it's called the BCS theory
of superconductivity and it's an incredible theory. It predicts many of the phenomena
that have been seen and also new phenomena that were quickly tested so we understand that very
well but that theory tells us that they can't possibly exist above about 40 degrees C above
absolute zero. So it was a complete surprise when in 1984 another group found materials that that
theory says couldn't possibly superconduct in fact does and does it much higher temperatures.
A lot of progress has been made in terms of the experimental approach to discovering high
temperature superconductors. So after that initial find, if you were to plot a graph of highest
temperature achieved versus time, you'd see that we jump from the low temperature ones - there's a
big jump up to this new type of high temperature - and then the highest temperature increases with
time because we found a lot of related compounds to that initial discovery. And then a totally
different family of superconductors was found in a different material so we have this sort of process
of going up and eventually petering out and then a totally new species perhaps starting with a lower
temperature initially but shooting up to a higher value and this has happened a few times now so you
see this repeated process of discovering a whole family and the temperature is creeping up each
time this happens. I'm speaking from a biased point of view as a theoretical physicist myself
but I would say that a theory of high temperature superconductivity is the most pressing subject in
condensed matter physics and one of the biggest questions in all of physics. And
if we understood how they work we could probably quite easily predict which classes of materials
would superconduct at room temperature and higher so we would instantly get many
practical applications. So guessing new material groups is tricky uh I I don't know the magic
that experimental physicists do to find these new materials I think there's an element of guesswork
there. From a theoretical point of view I can say that from the discovery of low temperature
superconductors in 1911 it took about 40 years or so until the theory was understood. The first
high temperature superconductors were discovered in the mid 80s and so it's pretty much the time
now that we would expect to be coming up with a theory if you made just the simple assertion
that it would take the same length of time so we could be quite hopeful that we might make
that discovery soon. Okay so some practical applications that are in the very near future
I think actually are creating power lines out of high temperature superconductors because that's
actually already being done in Essen and Germany they have power lines that use superconductors
and they're buried underground rather than going above ground so they can be cooled.
They're already being produced for use in various places in the United States. One of the really
appealing applications that's upcoming is that the engineering is underway to connect up three
major power grids in the United States - the East Coast the West Coast and Texas - and this process
of coupling those three grids would allow the power to be balanced across the country because
of course they're in different time zones and so on. So demand is different at different times. And
it turns out to be much more energy efficient to couple those grids using a superconductor in one
place you really need to pass them into one region and couple them. The amount of energy you would
use dissipating the heat out of that area from normal current turns out to be a lot more than
it would be if you cool down a superconductor to it. And of course one of the major upcoming
applications is likely to be Quantum Computing, so the some of the most promising routes to
making scalable useful quantum computers employ superconductors. So the topic of superconductivity
is one of various different topics I discuss in my recent book 'The Magick of Matter: Crystals,
Chaos and the Wizardry of Physics', which introduces the broader subject of condensed
matter physics and shows some of the applications and also why the subject is rather magical.