# Extended Magnetic Dome Induced by Low Pressures in Superconducting FeSe$_\mathrm{1\text{-}x}$S$_\mathrm{x}$

## TL;DR

This study reveals that in FeSe$_{1-x}$S$_x$, applying pressure induces an extended magnetic dome that coexists with superconductivity, affecting the critical temperature and suggesting a complex interplay between magnetism and superconductivity.

## Contribution

It demonstrates the emergence of a long-range magnetic order coexisting with superconductivity under pressure in FeSe$_{1-x}$S$_x$, extending the known magnetic phases and their relationship with superconductivity.

## Key findings

- Microscopic coexistence of magnetism and superconductivity above 0.6 GPa.
- Magnetic order influences the pressure dependence of $T_c$.
- Extrapolation suggests magnetic and superconducting states at ambient pressure for higher S content.

## Abstract

We report muon spin rotation ($\mu$SR) and magnetization measurements under pressure on Fe$_{1+\delta}$Se$_\mathrm{1\text{-}x}$S$_\mathrm{x}$ with x $\approx 0.11$.Above $p\approx0.6$ GPa we find microscopic coexistence of superconductivity with an extended dome of long range magnetic order that spans a pressure range between previously reported separated magnetic phases. The magnetism initially competes on an atomic scale with the coexisting superconductivity leading to a local maximum and minimum of the superconducting $T_\mathrm{c}(p)$. The maximum of $T_\mathrm{c}$ corresponds to the onset of magnetism while the minimum coincides with the pressure of strongest competition. A shift of the maximum of $T_\mathrm{c}(p)$ for a series of single crystals with x up to 0.14 roughly extrapolates to a putative magnetic and superconducting state at ambient pressure for x $\geq0.2$.