# Dome of magnetic order inside the nematic phase of sulfur-substituted FeSe under pressure

## TL;DR

This study investigates how sulfur substitution and pressure influence magnetic, structural, and superconducting properties in FeSe, revealing a dome-shaped magnetic order and complex pressure-dependent superconducting behavior.

## Contribution

It provides new insights into the interplay of chemical and physical pressure effects on magnetic order and superconductivity in sulfur-substituted FeSe.

## Key findings

- Magnetic order is suppressed to a small dome with sulfur substitution.
- Superconducting transition temperature exhibits non-monotonic pressure dependence.
- Emergence of magnetic order correlates with a local maximum in T_c.

## Abstract

The pressure dependence of the structural, magnetic and superconducting transitions and of the superconducting upper critical field were studied in sulfur-substituted Fe(Se$_{1-x}$S$_{x}$). Resistance measurements were performed on single crystals with three substitution levels ($x$=0.043, 0.096, 0.12) under hydrostatic pressures up to 1.8 GPa and in magnetic fields up to 9 T, and compared to data on pure FeSe. Our results illustrate the effects of chemical and physical pressure on Fe(Se$_{1-x}$S$_{x}$). On increasing sulfur content, magnetic order in the low-pressure range is strongly suppressed to a small dome-like region in the phase diagrams. However, $T_s$ is much less suppressed by sulfur substitution and $T_c$ of Fe(Se$_{1-x}$S$_{x}$) exhibits similar non-monotonic pressure dependence with a local maximum and a local minimum present in the low pressure range for all $x$. The local maximum in $T_c$ coincides with the emergence of the magnetic order above $T_c$. At this pressure the slope of the upper critical field decreases abruptly. The minimum of $T_c$ correlates with a broad maximum of the upper critical field slope normalized by $T_c$.