Anisotropic multiband superconductivity in 2M-WS$_{2}$ probed by controlled disorder

TL;DR

This study investigates the bulk superconducting properties of 2M-WS$_{2}$, revealing anisotropic multiband superconductivity with unconventional temperature dependence and disorder effects, relevant for topological surface state superconductivity.

Contribution

It provides the first detailed experimental characterization of the bulk superconducting state in 2M-WS$_{2}$, demonstrating anisotropic multiband superconductivity with disorder effects.

Findings

Power-law temperature dependence of penetration depth ($T^3$)

Significant suppression of $T_c$ with nonmagnetic disorder

Evidence for anisotropic $s^{++}$ multiband superconductivity

Abstract

The intrinsically superconducting Dirac semimetal 2M-WS$_{2}$ is a promising candidate to realize proximity-induced topological superconductivity in its protected surface states. A precise characterization of the bulk superconducting state is essential for understanding the nature of surface superconductivity in the system. Here, we perform a detailed experimental study of the temperature and nonmagnetic disorder dependence of the London penetration depth $\lambda$, the upper critical field $H_{c2}$, and the superconducting transition temperature $T_c$ in 2M-WS$_{2}$. We observe a power-law dependence $\lambda(T) - \lambda(0) \propto T^{3}$ at temperatures below $0.35~T_c$, which is remarkably different from the expected exponential attenuation of a fully gapped isotropic $s$-wave superconductor. We then probe the effect of controlled nonmagnetic disorder induced by 2.5 MeV electron irradiation at various doses and find a significant $T_c$ suppression rate. Together with the observed increase of the slope $dH_{c2}/dT|_{T=T_c}$ with irradiation, our results reveal a strongly anisotropic $s^{++}$ multiband superconducting state that takes the same sign on different Fermi sheets. Our results have direct consequences for the expected proximity-induced superconductivity of the topological surface states.