Superconductivity in the Superhard Boride WB$_{4.2}$

TL;DR

This paper reports that the superhard boride WB₄.₂ exhibits superconductivity at 2.05 K, with detailed measurements indicating a possibly strong coupling superconductor, expanding the understanding of superconductivity in superhard materials.

Contribution

The study demonstrates superconductivity in WB₄.₂, a superhard boride, providing new insights into its physical properties and superconducting behavior.

Findings

Superconducting transition at 2.05 K.

Higher than expected / T_c ratio.

Upper critical field between linear extrapolation and WHH model.

Abstract

We show that the superhard boride WB$_{4.2}$ is a superconductor with a T$_c$ of 2.05(5) K. Temperature-dependent magnetic susceptibility, electrical resistivity, and specific heat measurements were used to characterize the superconducting transition. The Sommerfeld constant {\gamma} for WB$_{4.2}$ is 2.07(3) mJ mol$^{-1}$ K$^{-2}$ and the {\Delta}C/{\gamma}T$_c$ = 1.56, which is somewhat higher than what is expected for weakly coupled BCS type superconductors. The H$_{c2}$ vs T plot is linear over a wide temperature range but does show signs of flattening by the lowest temperatures studied and therefore the zero-temperature upper critical field ({\mu}$_0$H$_{c2}$(0)) for WB$_{4.2}$ lies somewhere between the linear extrapolation of {\mu}$_0$H$_{c2}$(T) to 0 K and expectations based on the WHH model.