title: Valence band x-ray emission spectra of compressed germanium.
abstract: 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.
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road NW, Washington, DC 20015, USA.
authors.forename: Viktor V
authors.initials: VV
authors.lastname: Struzhkin
authors.forename: Ho-kwang
authors.initials: HK
authors.lastname: Mao
authors.forename: Jung-Fu
authors.initials: JF
authors.lastname: Lin
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Hemley
authors.forename: John S
authors.initials: JS
authors.lastname: Tse
authors.forename: Yanming
authors.initials: Y
authors.lastname: Ma
authors.forename: Michael Y
authors.initials: MY
authors.lastname: Hu
authors.forename: Paul
authors.initials: P
authors.lastname: Chow
authors.forename: Chi-Chang
authors.initials: CC
authors.lastname: Kao