14 | New Scientist | 24 October 2020
Materials scienceACHIEVING room temperature
superconductivity, a major goal
in materials science for decades,
may finally have been cracked,
with the potential to revolutionise
the way we use electricity.
An enormous amount of the
energy we produce is wasted
because of electrical resistance,
which generates heat. But in a
superconducting material,
electrical current can flow
with zero resistance, meaning
these losses don’t occur.
This property has made
such materials sought-after,
but until now getting them
to work has required very
low temperatures and
extremely high pressures.Under pressure
“If you had a room-temperature
superconductor that you could
deploy at atmospheric pressure,
you could imagine a whole host
of large-scale applications,” says
M. Brian Maple at the University
of California, San Diego.
Ranga Dias at the University
of Rochester, New York, and his
colleagues have gone part of
the way to addressing those
requirements. The team made
a superconductor by crushing
carbon, sulphur and hydrogen
between two diamonds at a
pressure about 70 per cent of that
found at the centre of Earth and
at a temperature of around 15°C.
That is the highest temperature
at which superconductivity has
ever been measured, and the first
such material that can reasonably
be said to have this property at
room temperature (Nature,
doi.org/ghfp4w).
The new approach was partially
inspired by the idea that solid
metallic hydrogen is expected
to be superconductive, but it is
incredibly difficult to makebecause it requires extraordinary
pressure. The researchers found
that adding carbon and sulphur to
hydrogen makes it behave as if it
is at a higher pressure than it is.
“Say you are in a room and you
have four walls. One way you can
compress yourself is to bring the
walls closer and closer, but you can
also keep the same size of room
and add 10 people into the room,
you’ll still feel squeezed,” says Dias.
In this experiment, adding carbon
and sulphur to the hydrogen is like
adding more people to the room:
it acts to chemically pre-compress
the hydrogen.
Once Dias and his team found
that the electrical resistance of
their material went to zero at 15°C,
they did other tests to confirm
that it really was superconductive,
such as making sure it blocked
magnetic fields.
“These are very thorough
experiments, they basically nailed
it down. When you look at the
data, it’s stunning,” says Shanti
Deemyad at the University of Utah.Two diamonds were
used to crush a mix
of three elementsLeah CraneADAMFENS
TE
RNews
15°C
Temperature at which the new
material operates – a record high70%
of the pressure found at the
centre of Earth is required to
produce the superconductorSuperconductors are hot again
A material with zero electrical resistance could spark an energy revolution
“This is going to shake the field.”
Questions still remain, though.
For example, despite knowing that
the superconducting material is
made of carbon, sulphur and
hydrogen, we don’t know how
those elements are bonded. “It’s
not uncommon in this type of
research to have an experiment
without knowing the structure,”
says Eva Zurek at the State
University of New York at Buffalo.
More theoretical work will be
needed to match the material’s
behaviour with models of various
compounds to figure out exactly
what it is, she says.
Maple also cautions that there
may be formidable challenges
ahead. It is possible these could be
so great that you might not be able
to get a superconductor that can
perform well enough for many
hoped-for applications, he says.
Dias and his team are working
to produce their material at lower
pressures. “Take diamond: it is a
high-pressure form of carbon, but
nowadays you can grow it in a lab
with chemical deposition,” says
Dias. “It used to require high
pressure, but now we can grow it.
We may be able to do something
similar with superconductors.”
The fact that this compound has
three elements in it, whereas other
superconductors have tended to
only contain one or two, makes it
more adjustable, which Dias says
will help in the effort to make it
work at lower pressures.
If that can be achieved, this
material could be used in
applications ranging from
quantum computing to building
better MRI machines to drastically
reducing energy waste from
electricity transmission. “If we
could make superconducting
wires that we didn’t have to cool,
we could in principle replace the
whole power grid,” says Zurek.
“That would be a real revolution.” ❚