Simultaneous Observation of Fishtail Effect and Peak Effect in 2H-Nbse$_2$

TL;DR

This study reports the simultaneous observation of Fishtail and Peak Effects in 2H-NbSe$_2$, revealing reentrant order-disorder transitions in the vortex lattice near the superconducting transition temperature.

Contribution

It provides the first detailed angular dependence study showing concurrent Fishtail and Peak Effects in 2H-NbSe$_2$, clarifying vortex matter phase transitions.

Findings

Fishtail Effect and Peak Effect are observed simultaneously.

Reentrant order-disorder transition in vortex lattice is established.

Ordered vortex state exists between two anomalous current density variations.

Abstract

We report on the discovery of the simultaneous observation of Fishtail Effect (FE) and Peak Effect (PE) via the study of angular dependence of dc magnetization hysteresis loops in a clean crystal of 2H-NbSe$_2$. These result clarify and establish the occurrence of the reentrant characteristics in order to disorder transformation in an isothermal scan close to zero field superconducting transition temperature of 2H-NbSe$_2$. The ubiquitous FE arises from coalescence of two anomalous variations in current density J$_c$, one of which is related to the collapse of the rigidity FLL close to H$_{c2}$ and another one located at very low fields presumably corresponds to the pinning induced order to disorder transformation. When the two effects get well separated, an ordered state of FLL exists in the intermediate field region.