Instabilities in the vortex matter and the peak effect phenomenon

TL;DR

This paper investigates vortex matter in 2H-NbSe2 crystals, revealing a crossover from weak to strong pinning unrelated to the peak effect, and mapping these transitions in the phase diagram.

Contribution

It identifies a new vortex pinning crossover not associated with the peak effect and maps the phase boundaries in the vortex matter phase diagram.

Findings

Pinning crossover is not linked to the peak effect.

A boundary separates strong pinning from thermal fluctuation dominance.

Peak effect appears at the boundary with thermal fluctuations.

Abstract

In single crystals of 2H-NbSe2, we identify for the first time a crossover from weak collective to strong pinning regime in the vortex state which is not associated with the peak effect phenomenon. Instead, we find the crossover is associated with anomalous history dependent magnetization response. In the field (Bdc) - temperature (T) vortex matter phase diagram we demarcate this pinning crossover boundary. We also delineate another boundary which separates the strong pinning region from a thermal fluctuation dominated regime, and find that PE appears on this boundary.