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.