Large Broadening of the Superconducting Transition by Fluctuations in a 3D Metal at High Magnetic Fields: The MgB$_{2}$ case

TL;DR

This paper demonstrates that thermal fluctuations significantly broaden the superconducting transition in MgB$_{2}$ under high magnetic fields, leading to an extended vortex liquid state below the mean-field upper critical field.

Contribution

It provides a quantitative analysis of fluctuation effects on the superconducting transition in a 3D metal, specifically applying it to MgB$_{2}$ and explaining experimental observations.

Findings

Superconducting transition is dramatically smeared by fluctuations.

Vortex liquid state extends below the mean-field $H_{c2}$.

Good agreement with experimental dHvA oscillation data.

Abstract

It is shown that the transition to the low temperature superconducting state in a 3D metal at high magnetic field is smeared dramatically by thermal fluctuation of the superconducting order parameter. The resulting superconducting-to-normal crossover occurs in a vortex liquid state which is extended well below the mean-field $H_{c2}$. Application to MgB$_{2}$ yields good quantitative agreement with recently reported data of dHvA oscillation in the superconducting state.