Growth and hydrostatic-pressure study of a type-II superconductor Bi$_2$Ta$_3$S$_6$ single crystal

TL;DR

This study reports the growth, physical properties, and topological features of Bi$_2$Ta$_3$S$_6$ single crystals, revealing superconductivity at 0.84 K, type-II behavior, and non-trivial topological surface states, with effects of hydrostatic pressure analyzed.

Contribution

First comprehensive analysis of Bi$_2$Ta$_3$S$_6$ single crystals including growth, superconducting properties, and topological surface states, highlighting potential for topological superconductivity.

Findings

Superconducting transition at 0.84 K

Type-II superconductor with anisotropic parameters

Presence of non-trivial topological surface states

Abstract

We report the growth and physical properties of single-crystalline Bi$_2$Ta$_3$S$_6$ crystallizing in $P6_3/mcm$ space group, which comprises alternating Ta-S layers and Bi layers with each Bi atom connected with adjacent S atoms. Temperature-dependent electrical resistivity measurements reveal a superconducting transition at 0.84 K, with upper critical field 231 Oe under an out-of-plane magnetic field. The magnetization measurements confirm its nature as a type-II superconductor, with anisotropic Ginzburg-Landau parameter $\kappa_{ab}$ = 7.67 and $\kappa_c$ = 4.50. Hall measurements indicate the dominant carriers as hole. Hydrostatic pressure is applied, under which both the superconducting transition temperature and upper critical field increase sharply under low pressure before undergoing slight suppression under higher pressure. Density functional theory calculations reveal non-trivial topological surface states on (100) surface in Bi$_2$Ta$_3$S$_6$, which may offer a new avenue for exploring potential topological superconductivity in layered transition metal dichalcogenides.