Superconductivity in Boron
Mikhail I. Eremets,12
Viktor V. Struzhkin,1
Ho-kwang Mao,1
Russell J. Hemley1*
Metals formed from light elements are predicted to exhibit
intriguing states of electronic order. Of these materials, those containing boron are of considerable current interest because of their
relatively high superconducting temperatures. We have investigated
elemental boron to very high pressure using diamond anvil cell
electrical conductivity techniques. We find that boron transforms from
a nonmetal to a superconductor at about 160 gigapascals (GPa). The
critical temperature of the transition increases from 6 kelvin (K) at
175 GPa to 11.2 K at 250 GPa, giving a positive pressure derivative of
0.05 K/GPa. Although the observed metallization pressure is compatible
with the predictions of first-principles calculations,
superconductivity in boron remains to be explored theoretically. The
present results constitute a record pressure for both electrical
conductivity studies and investigations of superconductivity in dense
matter.
1 Geophysical Laboratory and Center for High
Pressure Research, Carnegie Institution of Washington, 5251 Broad
Branch Road, NW, Washington, DC 20015, USA.
2 Max-Planck Institut für Chemie, Postfach
3060, 55020 Mainz, Germany.
*
To whom correspondence should be addressed. E-mail:
hemley{at}gl.ciw.edu
