The Anisotropy of Thermal Activation Energy of 2H-NbS$_2$

TL;DR

This study explores the anisotropic flux dynamics in 2H-NbS2 superconductors, revealing distinct thermal activation energy behaviors under different magnetic field orientations, highlighting its potential as a model for layered superconductor flux studies.

Contribution

It provides the first detailed analysis of anisotropic flux dynamics and thermal activation energy scaling in 2H-NbS2, demonstrating different behaviors for in-plane and out-of-plane magnetic fields.

Findings

U0 follows Arrhenius law for out-of-plane fields

U0 exhibits modified TAFF behavior for in-plane fields

Evidence of two-dimensional vortex behavior in 2H-NbS2

Abstract

We investigate the anisotropic flux dynamics in 2H-NbS$_2$ single crystals through temperature-dependent resistance measurements under in-plane ($H \parallel ab$ plane) and out-of-plane ($H \perp ab$ plane) magnetic fields. Analysis of thermally activated flux flow (TAFF) resistance in the superconducting mixed state reveals stark contrasts in thermal activation energy ($U_0$) scaling and field dependence. For $H \perp ab$, $U_0(0.1 \mathrm{T}) = (1228.76 \pm 53.64)$ K follows the Arrhenius relation with a power-law field decay ($U_0\propto H^{-\alpha}$). In contrast, under $H \parallel ab$, $U_0(0.5 \mathrm{T}) = (7205.58 \pm 619.65)$ K aligns with the modified TAFF theory, where the scaling exponent $q = 2$ potentially reflects two-dimensional vortex behavior in the TAFF region, and the field dependence of $U_0$ follows parabolic relation $H^{\gamma}\left[1 - \frac{H}{H^{*}}\right]^2$. These results establish 2H-NbS$_2$ as a model system for probing the anisotropy of flux dynamics in layered superconductors.