Enhanced weak superconductivity in trigonal $\gamma$-PtBi$_2$

TL;DR

This study reports enhanced superconductivity in trigonal $ extgamma$-PtBi$_2$ with high critical fields and low critical currents, indicating an inhomogeneous superconducting state distinct from typical bulk behavior.

Contribution

The paper presents the first observation of enhanced superconductivity in high-quality trigonal $ extgamma$-PtBi$_2$ with record critical fields and unusual anisotropy at ambient pressure.

Findings

Superconductivity at $T_c=1.1$ K in trigonal $ extgamma$-PtBi$_2$

High critical magnetic field $ o 1.5$ Tesla

Inhomogeneous superconducting state suggested by broad transition

Abstract

Electrical resistivity experiments show superconductivity at $T_c = 1.1\,$K in a high-quality single crystal of trigonal $\gamma$-PtBi$_2$, with an enhanced critical magnetic field $\mu_0H_{c2}(0) \gtrsim 1.5\,$Tesla and a low critical current-density $J_c(0)\approx 40\,\mathrm{A}/\mathrm{cm}^2$ at $H=0$. Both $T_c$ and $H_{c2}(0)$ are the highest reported values for stoichiometric bulk samples at ambient pressure. We found a weak $H_{c2}$ anisotropy with $\Gamma=H_{c2}^{ab}/H_{c2}^{c} < 1$, which is unusual among superconductors. Under a magnetic field, the superconducting transition becomes broader and asymmetric. Along with the low critical currents, this observation suggests an inhomogeneous superconducting state. In fact, no trace of superconductivity is observed through field-cooling--zero-field-cooling magnetization experiments.