Pressure-Induced Alloying and Superconductivity in GeTe

Here, we systematically investigated the pressure dependence
of
electronic transport and the crystal structure of GeTe using multiple
methods under various hydrostatic conditions. The experiments indicated
that a progressive structural evolution occurred from the ambient
rhombohedral phase (space group [SG]: R3m) to the rock-salt phase (SG: Fm3̅m) and then to an orthorhombic phase (SG: Pnma). Above 50 GPa, we determined that GeTe developed into
a body-centered cubic (bcc, SG: Im3̅m) structure, which consisted of a site-disordered alloy.
An unambiguous correlation between superconductivity and phase transitions
was observed in this compound, and the maximum superconducting transition
temperature (Tc) was approximately 7.5
± 0.2 K at 30.0(1) GPa. Finally, the key effect of ionic size
and charge transfer between the Ge and Te ions on the formation of
site-disordered alloys in GeTe was discussed.