Vortex-glass transformation within the surface superconducting state of $\beta$-phase Mo$_{1-x}$Re$_x$ alloys

TL;DR

This study investigates the vortex-glass transition within the surface superconducting state of Mo-Re alloys, revealing surface superconductivity, flux-line pinning, and a vortex-liquid to vortex-glass transition through resistivity and heat capacity measurements.

Contribution

It provides experimental evidence of surface superconductivity and vortex-glass transition in Mo-Re alloys, highlighting the flux-spot model and surface vortex dynamics.

Findings

Surface superconductivity persists above bulk T_c in magnetic fields.

Evidence of vortex-glass transition within the surface state.

Flux-line configuration described by the flux-spot model.

Abstract

We have performed an experimental study on the temperature dependence of electrical resistivity $\rho$($T$) and heat capacity $C$($T$) of the Mo$_{1-x}$Re$_x$ $(x = 0.20, 0.25)$ alloy superconductors in different magnetic fields. In the presence of applied magnetic field, the electrical resistivity of these alloys go to zero at a temperature well above the bulk superconducting transition temperature obtained with the help of heat capacity measurements in the same magnetic field. Our study indicates the presence of surface superconducting state in these alloys, where the flux lines are pinned in the surface sheath of the superconductor. The configuration of the flux-lines (2d pancake-like) in the surface sheath is understood in the realm of the flux-spot model. Experimental evidence in support of the surface mixed-state state or "Kulik vortex-state" and the occurrence of a vortex-liquid to vortex-glass transition is presented.