Temperature and time scaling of the peak-effect vortex configuration in FeTe$_{0.7}$Se$_{0.3}$

TL;DR

This study investigates the vortex behavior in FeTe$_{0.7}$Se$_{0.3}$ superconductors, revealing weak collective pinning, a peak effect in magnetization, and temperature-independent vortex configurations.

Contribution

It provides the first detailed analysis of the temperature and time scaling of the peak-effect vortex configuration in FeTe$_{0.7}$Se$_{0.3}$, highlighting the dominance of $ ext{δ}l$ pinning and temperature-independent vortex arrangements.

Findings

Weak collective pinning from spatial charge carrier variations.

Peak effect in magnetization shifts with temperature but vortex configuration remains constant.

Vortex-vortex interactions are unaffected by temperature in the studied range.

Abstract

An extensive study of the magnetic properties of FeTe$_{0.7}$Se$_{0.3}$ crystals in the superconducting state is presented. We show that weak collective pinning, originating from spatial variations of the charge carrier mean free path ($\delta l$ pinning), rules in this superconductor. Our results are compatible with the nanoscale phase separation observed on this compound and indicate that in spite of the chemical inhomogeneity spatial fluctuations of the critical temperature are not important for pinning. A power law dependence of the magnetization vs time, generally interpreted as signature of single vortex creep regime, is observed in magnetic fields up to $8 ~ T$. For magnetic fields applied along the c axis of the crystal the magnetization curves exhibit a clear peak effect whose position shifts when varying the temperature, following the same dependence as observed in YBa$_2$Cu$_3$O$_{7-\delta}$. The time and temperature dependence of the peak position has been investigated. We observe that the occurrence of the peak at a given magnetic field determines a specific vortex configuration that is independent on the temperature. This result indicates that the influence of the temperature on the vortex-vortex and vortex-defect interactions leading to the peak effect in FeTe$_{0.7}$Se$_{0.3}$ is negligible in the explored range of temperatures.