Valence band x-ray emission spectra of compressed germanium.
We report measurements of the valence band width in compressed Ge determined from x-ray emission spectra below the Ge K edge. The width of the valence band does not show any pressure dependence in the semiconducting diamond-type structure of Ge below 10 GPa. On the other hand, in the metallic beta-Sn phase above 10 GPa the valence band width increases under compression. Density-functional calculations show an increasing valence band width under compression both in the semiconducting phase (contrary to experiment) and in the metallic beta-Sn phase of Ge (in agreement with observed pressure-induced broadening). The pressure-independent valence band width in the semiconducting phase of Ge appears to require theoretical advances beyond the density-functional theory or the GW approximation.
Struzhkin
Viktor V
VV
Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.
Mao
Ho-kwang
HK
Lin
Jung-Fu
JF
Hemley
Russell J
RJ
Tse
John S
JS
Ma
Yanming
Y
Hu
Michael Y
MY
Chow
Paul
P
Kao
Chi-Chang
CC