Magnetization Properties and Vortex Phase Diagram in CuxTiSe2 Single Crystals

TL;DR

This study explores the magnetization and vortex phase behavior in Cu$_x$TiSe$_2$ single crystals, revealing low and doping-independent anisotropy, a broad vortex liquid region, and minimal impact of copper fluctuations on pinning.

Contribution

It provides new insights into the vortex phase diagram and anisotropy in Cu$_x$TiSe$_2$, highlighting the effects of copper doping on superconducting properties.

Findings

Superconducting anisotropy is approximately 1.7, increasing slightly in underdoped samples.

Vortex liquid phase is unusually broad for low-$T_c$ superconductor with low anisotropy.

Critical current densities are low compared to the depairing current limit, with little effect from copper concentration fluctuations.

Abstract

We have investigated the magnetization properties and flux dynamics of superconducting Cu$_x$TiSe$_2$ single crystals within wide range of copper concentrations. We find that the superconducting anisotropy is low and independent on copper concentration ($\gamma\sim1.7$), except in the case of strongly underdoped samples ($x\leq0.06$) that show a gradual increase in anisotropy to $\gamma\sim1.9$. The vortex phase diagram in this material is characterized by broad region of vortex liquid phase that is unusual for such low-$T_c$ superconductor with low anisotropy. Below the irreversibility line the vortex solid state supports relatively low critical current densities as compared to the depairing current limit ($J_c/J_0\sim10^{-7}$). All this points out that local fluctuations in copper concentration have little effect on bulk pinning properties in this system.