Pressure-induced superconductivity in the weak topological insulator Bi2TeI and the topological metal Bi3TeI

TL;DR

This study demonstrates that applying high pressure induces structural transitions in Bi2TeI and Bi3TeI, leading to superconductivity in their disordered bcc phases with maximum Tc around 7-7.5 K.

Contribution

It reveals pressure-induced superconductivity in Bi2TeI and Bi3TeI and identifies their high-pressure phases as disordered bcc alloys, contrasting previous structural assumptions.

Findings

Superconductivity appears at 13 GPa for Bi2TeI and 11.5 GPa for Bi3TeI.

Maximum Tc reaches 7 K for Bi2TeI and 7.5 K for Bi3TeI.

Disordered bcc alloy phases are a universal high-pressure feature in these systems.

Abstract

We report a series of high-pressure electrical transport, magnetic susceptibility, and x-ray diffraction measurements on single crystals of the weak topological insulator Bi2TeI and the topological metal Bi3TeI. Room temperature x-ray diffraction measurements show that both materials go through a series of pressure-induced structural transitions and eventually adopt a disordered bcc alloy structure at high pressure. A re-analysis of the published data on BiTeI indicates that this material also adopts a disordered bcc structure at high pressure, in contrast to the previously suggested P4/nmm structure. We find that Bi2TeI and Bi3TeI become superconducting at 13 GPa and 11.5 GPa, respectively. The superconducting critical temperature Tc of the bcc phase reaches maximum values of 7 K and 7.5 K for Bi2TeI and Bi3TeI, respectively and dTc/dP < 0 in both cases. The results indicate that disordered alloy bcc superconducting phases appear to be a universal feature of both the Bi-Te and Bi-Te-I systems at high pressure.