Peak Effect, Fishtail Effect and Plateau Effect : The Reentrant Amorphization of Vortex Matter in 2H-NbSe_2

TL;DR

This study investigates the vortex matter phase transitions in 2H-NbSe2, revealing how different pinning regimes and amorphous limits lead to peak, fishtail, and plateau effects in the critical current near phase boundaries.

Contribution

It provides new insights into the reentrant vortex phase diagram and pinning regimes, linking amorphous limits to peak and plateau effects in a superconductor.

Findings

Identification of various pinning regimes in 2H-NbSe2

Demonstration of amorphous limit approaching near the peak effect

Observation of peak, fishtail, and plateau effects related to disorder and vortex phases

Abstract

The magnetic field dependence of the critical current is studied in single crystal samples of the weak pinning type-II superconductor 2H-NbSe$_2$ in the high temperature and the low field region of the (H,T) phase space, in the vicinity of the reentrant peak effect. The experimental results demonstrate various pinning regimes : a collective pinned quasi-ordered solid in the intermediate field that is destabilized in favor of disordered vortex phases in both high fields near H$_{c2}$ and at low fields near H$_{c1}$. The temperature evolution of the pinning behavior demonstrates how the amorphous limit (where the correlation volume is nearly field independent) is approached around the so-called nose region of the reentrant peak effect boundary. Furthermore, the data show that the rapid approach to the amorphous limit naturally yields a peak effect, i.e., a peak in the critical current, in the high field regime, but yields a ``plateau effect'' instead in the low field regime in an analogous way. With increasing effective disorder the peak effect shifts away from H$_{c2}$ and resembles a ``fishtail'' anomaly.