# Weakening of the diamagnetic shielding in FeSe$_{1-x}$S$_x$ at high pressures

## TL;DR

This study investigates how hydrostatic pressure affects the superconducting properties of FeSe$_{1-x}$S$_x$, revealing a weakening of diamagnetic shielding at high pressures indicating competition between magnetic and superconducting states.

## Contribution

It provides new insights into the pressure-dependent superconducting and magnetic phase interplay in FeSe$_{1-x}$S$_x$ with multiple sulphur concentrations.

## Key findings

- Superconducting transition temperature $T_c$ exhibits a dome-shaped variation with pressure.
- Diamagnetic shielding weakens significantly beyond the pressure where $T_c$ peaks.
- High pressure induces a competition between magnetic order and superconductivity.

## Abstract

The superconducting transition of FeSe$_{1-x}$S$_x$ with three distinct sulphur concentrations $x$ was studied under hydrostatic pressure up to $\sim$70 kbar via bulk AC susceptibility. The pressure dependence of the superconducting transition temperature ($T_c$) features a small dome-shaped variation at low pressures for $x=0.04$ and $x=0.12$, followed by a more substantial $T_c$ enhancement to a value of around 30 K at moderate pressures. In $x=0.21$, a similar overall pressure dependence of $T_c$ is observed, except that the small dome at low pressures is flattened. For all three concentrations, a significant weakening of the diamagnetic shielding is observed beyond the pressure around which the maximum $T_c$ of 30 K is reached near the verge of pressure-induced magnetic phase. This observation points to a strong competition between the magnetic and high-$T_c$ superconducting states at high pressure in this system.