Growth, Characterization, Vortex Pinning and Vortex Flow Properties of Single Crystals of Iron Chalcogenide Superconductor FeCr$_{0.02}$Se

TL;DR

This study reports the growth and detailed characterization of FeCr$_{0.02}$Se$ superconducting single crystals, revealing enhanced T$_{ m c}$, vortex pinning mechanisms, and charge carrier properties crucial for understanding Fe-based superconductivity.

Contribution

The paper presents the first detailed growth, superconducting parameters, and vortex dynamics analysis of FeCr$_{0.02}$Se$ single crystals, highlighting the effects of Cr doping.

Findings

Superconducting transition temperature increased by 25% with Cr doping.

Critical current data indicates fluctuation in electronic mean free path ($l$) pinning mechanism.

Crossover from single vortex pinning to collective flux creep observed at higher magnetic fields.

Abstract

We report the growth and characterization of single crystals of iron chalcogenide superconductor FeCr$_{0.02}$Se. There is an enhancement of the superconducting transition temperature (T$_{\rm c}$) as compared to the T$_{\rm c}$ of the single crystals of the parent compound Fe$_{1+x}$Se by about 25%. The superconducting parameters such as the critical fields, coherence length, penetration depth and the Ginzburg-Landau parameter have been estimated for these single crystals. Analysis of the critical current data suggests a fluctuation in electronic mean free path induced ($\delta l$) pinning mechanism in this material. Thermally activated transport across the superconducting transition in the presence of external magnetic fields suggests a crossover from a single vortex pinning regime at low fields to a collective flux creep regime at higher magnetic fields. The nature of charge carriers in the normal state estimated from the Hall effect and thermal transport measurements could provide crucial information on the mechanism of superconductivity in Fe-based materials.