32
nanotimes
10-01 :: January 2010
News in Brief
Superconductivity //
Metal Hydrides for High Temperature Superconductivity
A
n international research team, comprising explanation? It could be a case of happenstance:
scientists working in the Sweden, UK, USA & the mass of the Y atom appears to be just right to
South Korea and led by Professor Rajeev Ahuja of generate vibrations that can cause this phenomenon,
Uppsala University now presents new findings for while Sc is too light and La too heavy.
better understanding of superconducting high-
pressure metal hydride systems. “As with all theoretical predictions, we hope that our
work will lead to experimental tests of the data.”,
In the present work, the research team utilized some says Professor Rajeev Ahuja. “The pressures for which
of the most sophisticated implementations of theore- we have predicted superconductivity to occur is well
tical methods available to carry out an in-depth study within the reach of contemporary techniques.”
of superconductivity in the metal hydrides ScH3,
YH3, and LaH3 over a wide pressure range. This “Nevertheless, we believe that experimentalists will
approach enabled the scientists to identify a general embrace the challenge to test these predictions,
trend in the behavior for all three metal hydrides: the since there is tremendous merit in understanding
superconducting state is strongest when the material the underlying physics of superconducting metallic
is weakest. hydrogen-rich systems.”
Put more precisely, this means that near those pres-
sures where a structural transformation is about to set Duck Young Kima, Ralph H. Scheichera, Ho-kwang
in and the material becomes dynamically unstable, Maoc, Tae W. Kangd, Rajeev Ahujaa: General trend for
the electron-phonon coupling (which is a measure of pressurized superconducting hydrogen-dense materials,
the strength of a superconducting phase) is highest In: PNAS Early Edition, January 26, 2010, DOI:10.1073/
and drives the critical temperature of superconducti- pnas.0914462107:
vity to its maximal value.

http://dx.doi.org/10.1073/pnas.0914462107
But the scientists also discovered several differences
between the three metal hydrides, despite their che-
mical similarities. Thus, it was found that a secondary
superconducting phase, which was earlier predicted
by researchers of the same team to exist in YH3, is
mysteriously absent in ScH3 and LaH3. What is the