Nearly isotropic superconductivity in layered Weyl semimetal WTe$_2$ at 98.5 kbar

TL;DR

This study reveals that WTe$_2$, a layered Weyl semimetal, exhibits nearly isotropic superconductivity at high pressure, with minimal field anisotropy and behavior consistent with conventional orbital depairing mechanisms.

Contribution

First detailed measurement of the superconducting anisotropy in WTe$_2$ showing nearly isotropic behavior despite its layered structure.

Findings

Upper critical field shows negligible anisotropy.

Angular dependence fits anisotropic mass model.

Anisotropy factor remains temperature independent at ~1.7.

Abstract

Layered transition metal dichalcogenide WTe$_2$ has recently attracted significant attention due to the discovery of an extremely large magnetoresistance, a predicted type-II Weyl semimetallic state, and the pressure-induced superconducting state. By a careful measurement of the superconducting upper critical fields as a function of the magnetic field angle at a pressure as high as 98.5 kbar, we provide the first detailed examination of the dimensionality of the superconducting condensate in WTe$_2$. Despite the layered crystal structure, the upper critical field exhibits a negligible field anisotropy. The angular dependence of the upper critical field can be satisfactorily described by the anisotropic mass model from 2.2 K ($T/T_c\sim0.67$) to 0.03 K ($T/T_c\sim0.01$), with a practically identical anisotropy factor $\gamma\sim1.7$. The temperature dependence of the upper critical field, determined for both $H\perp ab$ and $H\parallel ab$, can be understood by a conventional orbital depairing mechanism. Comparison of the upper critical fields along the two orthogonal field directions results in the same value of $\gamma\sim1.7$, leading to a temperature independent anisotropy factor from near $T_c$ to $<0.01T_c$. Our findings thus identify WTe$_2$ as a nearly isotropic superconductor, with an anisotropy factor among one of the lowest known in superconducting transition metal dichalcogenides.