Pressure-induced structural transitions between successional superconducting phases in GeTe

Being a best-known prototype of phase-change materials, GeTe was reported to possess many high-pressure phases, whose structural evolution and superconductivity remain under debate for decades. Herein, we systematically investigated the pressure dependence of electrical transport and the structural evolution of the GeTe via in situ angle-dispersive synchrotron x-ray diffraction and resistance measurements up to 55 GPa. At room temperature, the structural phase transitions from the initial rhombohedral phase to the Fm (3) over barm phase, and then to an orthorhombic Pnma phase, were observed at pressures of about 4 and 13.4 GPa, respectively. Furthermore, the metallization occurred at around 11 GPa, where the superconductivity could also be observed. With increasing pressure, the superconducting transition temperature increases monotonically from 5.7 to 6.4 K and then is independent of pressure above 23 GPa in the pure Pnma phase. These results provide insights into the pressure-dependent evolution of the structure and superconductivity in GeTe and have implications for the understanding of other IV-VI semiconductors at high pressure.