Strain-induced modulation of superconductivity in the GeTe crystal

Cheng-Yen Liu^1,2, Ya-Hsin Pai^1,3, Tsu-Lien Hung^1,4, Fan-Yun Chiu^1,5, Ranganayakulu K. Vankayala¹, Dong-Zhou Zhang⁷, Yi-Jia Tsai^1,8, Chih-Ming Lin⁸, Yang-Yuan Chen^1,9,10, Min-Nan Ou^1,6,9*

¹Institute of Physics, Academia Sinica, Taipei, Taiwan
²Department of Physics, Fudan University, Shanghai, China
³Department of Materials Science, Fudan University, Shanghai, China
⁴Core Facility Center, National Cheng Kung University, Tainan, Taiwan
⁵Mechanical and Mechatronics Systems Lab, Industrial Technology Research Institute, Hsinchu, Taiwan
⁶Research Center for Critical Issues, Academia Sinica, Tainan, Taiwan
⁷GeoSoilEnviroCARS, Argonne National Laboratory, Argonne, Illinois, USA
⁸Department of Physics, National Tsing Hua University, Hsinchu, Taiwan
⁹Graduate Institute of Applied Physics, National Chengchi University, Taipei, Taiwan
¹⁰Department of Applied Informatics, Fo Guang University, Yilan County, Taiwan

* Presenter:Min-Nan Ou, email:oumn@gate.sinica.edu.tw

Germanium telluride (GeTe) is a multifunctional material with both thermoelectric and phase-change applications, exhibiting intrinsic semiconducting behavior and a superconducting transition temperature TC of ~0.3 K at ambient pressure. However, the structure and superconductivity of GeTe under high pressure remain unclear. In this work, the pressure-dependent transport properties and the structural evolution of GeTe are studied using a diamond anvil cell. The superconductivity of GeTe is observed at an initial pressure of 6.3 GPa, with a superconducting transition temperature (Tc) of ~3 K, which increases to ~4.35 K at 10.9 GPa. Meanwhile, magnetic-field suppression of TC confirmed the superconducting nature of the material. According to the structural analysis, three phases are observed in GeTe: a low-pressure rhombohedral phase (P < ~6.3 GPa), an intermediate-pressure cubic phase (6.3–17.9 GPa), and a high-pressure orthorhombic phase (P > ~17.9 GPa). Superconductivity occurs within the pressure range of the cubic phase of GeTe, and we found that its emergence is strongly correlated with strain. We tend to say that superconductivity occurred due to strain induced by pressure rather than to the intrinsic properties of the cubic GeTe phase.

Keywords: Superconductivity, High-Pressure Diamond Anvil Cell, High-Pressure Phase Transition