Suppression of the Melting Line in a Weakly Disordered Flux-line System

TL;DR

This paper presents an analytic formula that accurately describes how quenched point pinning disorder suppresses the melting line in a layered superconductor, validated by extensive experimental data.

Contribution

The authors derive and validate an analytic formula for the suppression of the melting line due to disorder in a layered superconductor, linking it to the peak effect in critical current.

Findings

The formula fits experimental data over three orders of magnitude in magnetic field.

Disorder suppresses the melting line, correlating with the peak effect in critical current.

The suppression of the melting line can be quantitatively described by the proposed analytic expression.

Abstract

An analytic formula describing the suppression of the equilibrium melting line by quenched point pinning disorder is compared to data from ac susceptibility and magnetization measurements in the mixed phase of the layered dichalcogenide low T_c superconductor 2H-NbSe_2. This material exhibits a sharp peak effect in the critical current close to the upper critical field H_c2(T). Arguing that the disorder-suppressed melting line in this system is to be identified with the locus of peak positions of the critical current as magnetic field and temperature are varied, we demonstrate that this formula provides a remarkably accurate fit to the experimental data over three orders of magnitude in magnetic field.