Superconductivity in HfTe5 Induced via Pressures

TL;DR

This study discovers pressure-induced superconductivity in HfTe5 single crystals, revealing phase transitions and structural changes that correlate with the emergence of superconductivity, expanding understanding of topological insulators under pressure.

Contribution

It provides the first experimental evidence of superconductivity in HfTe5 induced by pressure and maps its phase diagram with structural and electronic transitions.

Findings

Superconductivity appears above ~5.5 GPa in HfTe5.

Maximum Tc of around 5 K at 20 GPa.

Structural phase transitions from Cmcm to C2/m and then to P-1 occur at specific pressures.

Abstract

Recently, ZrTe5 and HfTe5 are theoretically studied to be the most promising layered topological insulators since they are both interlayer weakly bonded materials and also with a large bulk gap in the single layer. It paves a new way for the study of novel topological quantum phenomenon tuned via external parameters. Here, we report the discovery of superconductivity and properties evolution in HfTe5 single crystal induced via pressures. Our experiments indicated that anomaly resistance peak moves to low temperature first before reverses to high temperature followed by disappearance which is opposite to the low pressure effect on ZrTe5. HfTe5 became superconductive above ~5.5 GPa up to at least 35 GPa in the measured range. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. High pressure Raman revealed that new modes appeared around pressure where superconductivity occurs. Crystal structure studies shown that the superconductivity is related to the phase transition from Cmcm structure to monoclinic C2/m structure. The second phase transition from C2/m to P-1 structure occurs at 12 GPa. The combination of transport, structure measurement and theoretical calculations enable a completely phase diagram of HfTe5 at high pressures.