University physical scientists synthesize new superconducting material, developing a process that may help ‘break down barriers and open the door to many potential applications.’
By Bob Marcotte, University of Rochester
October 14, 2020 -- Compressing simple molecular solids with
hydrogen at extremely high pressures, University
of Rochester engineers and physicists have, for the first time,
created material that is superconducting at room temperature.
Featured as the cover article in the
journal Nature,
the work was conducted by the lab of Ranga
Dias, an assistant professor of mechanical engineering and of physics
and astronomy.
Dias says developing materials that are
superconducting—without electrical resistance and expulsion of magnetic field
at room temperature—is the “holy grail” of condensed matter physics. Sought for
more than a century, such materials “can definitely change the world as we know
it,” Dias says.
In setting the new record, Dias and his
research team combined hydrogen with carbon and sulfur to photochemically
synthesize simple organic-derived carbonaceous sulfur hydride in a diamond
anvil cell, a research device used to examine miniscule amounts of materials
under extraordinarily high pressure.
The carbonaceous sulfur hydride
exhibited superconductivity at about 58 degrees Fahrenheit and a pressure of
about 39 million pounds per square inch (psi).
“Because of the limits of low
temperature, materials with such extraordinary properties have not quite
transformed the world in the way that many might have imagined. However, our
discovery will break down these barriers and open the door to many potential
applications,” says Dias, who is also affiliated with the University’s materials science and high-energy-density
physics programs.
Applications include:
- Power
grids that transmit electricity without the loss of up to 200 million
megawatt hours (MWh) of the energy that now occurs due to resistance in
the wires
- A
new way to propel levitated trains and other forms of transportation
- Medical
imaging and scanning techniques such as MRI and magnetocardiography
- Faster,
more efficient electronics for digital logic and memory device technology
“We live in a semiconductor society, and
with this kind of technology, you can take society into a superconducting
society where you’ll never need things like batteries again,” says Ashkan
Salamat of the University of Nevada Las Vegas, a coauthor of the discovery.
The amount of superconducting material
created by the diamond anvil cells is measured in picoliters—about the size of
a single inkjet particle.
The next challenge, Dias says, is
finding ways to create the room temperature superconducting materials at lower
pressures, so they will be economical to produce in greater volume. In
comparison to the millions of pounds of pressure created in diamond anvil
cells, the atmospheric pressure of Earth at sea level is about 15 psi.
Why room temperature matters
First discovered in 1911,
superconductivity gives materials two key properties. Electrical resistance
vanishes. And any semblance of a magnetic field is expelled, due to a
phenomenon called the Meissner effect. The magnetic field lines have to pass
around the superconducting material, making it possible to levitate such
materials, something that could be used for frictionless high-speed trains,
known as maglev trains.
Powerful superconducting electromagnets
are already critical components of maglev trains, magnetic resonance imaging
(MRI) and nuclear magnetic resonance (NMR) machines, particle accelerators and
other advanced technologies, including early quantum supercomputers.
But the superconducting materials used
in the devices usually work only at extremely low temperatures—lower than any
natural temperatures on Earth. This restriction makes them costly to
maintain—and too costly to extend to other potential applications. “The cost to
keep these materials at cryogenic temperatures is so high you can’t really get
the full benefit of them,” Dias says.
Previously, the highest temperature for
a superconducting material was achieved last year in the lab of Mikhail Eremets
at the Max Planck Institute for Chemistry in Mainz, Germany, and the Russell
Hemley group at the University of Illinois at Chicago. That team reported
superconductivity at -10 to 8 degrees Fahrenheit using lanthanum superhydride.
Researchers have also explored copper
oxides and iron-based chemicals as potential candidates for high temperature
superconductors in recent years. However, hydrogen—the most abundant element in
the universe —also offers a promising building block.
“To have a high temperature
superconductor, you want stronger bonds and light elements. Those are the two
very basic criteria,” Dias says. “Hydrogen is the lightest material, and the
hydrogen bond is one of the strongest.
“Solid metallic hydrogen is theorized to
have high Debye temperature and strong electron-phonon coupling that is
necessary for room temperature superconductivity,” Dias says.
However, extraordinarily high pressures
are needed just to get pure hydrogen into a metallic state, which was first achieved
in a lab in 2017 by Harvard University professor Isaac Silvera and
Dias, then a postdoc in Silvera’s lab.
A ‘paradigm shift’ for superconductors
And so, Dias’s lab at Rochester has
pursued a “paradigm shift” in its approach, using as an alternative,
hydrogen-rich materials that mimic the elusive superconducting phase of pure
hydrogen, and can be metalized at much lower pressures.
First the lab combined yttrium and
hydrogen. The resulting yttrium superhydride exhibited superconductivity at
what was then a record high temperature of about 12 degrees Fahrenheit and a
pressure of about 26 million pounds per square inch.
Next the lab explored covalent hydrogen-rich
organic-derived materials.
This work resulted in the carbonaceous sulfur hydride. “This presence of carbon
is of tantamount importance here,” the researchers report. Further
“compositional tuning” of this combination of elements may be the key to
achieving superconductivity at even higher temperatures, they add.
Other coauthors on the paper include
lead author Elliot Snider ’19 (MS), Nathan Dasenbrock-Gammon ’18 (MA), Raymond
McBride ’20 (MS), Kevin Vencatasamy ’21, and Hiranya Vindana (MS), all of the
Dias lab; Mathew Debessai of Intel Corporation, and Keith Lawlor of the
University of Nevada Las Vegas.
The project was supported with funding
from the National Science Foundation and the US Department of Energy’s
Stockpile Stewardship Academic Alliance Program and its Office of Science,
Fusion Energy Sciences. Preparation of the diamond surfaces was performed in
part at the University of
Rochester Integrated Nanosystems Center (URnano).
Dias and Salamat have started a new
company, Unearthly Materials to find a path to room temperature superconductors
that can be scalably produced at ambient pressure.
Patents are pending.
= = = = = = = = = = = = = = = = == = = =
= = = = = = = = = =
No comments:
Post a Comment