Hydrothermal synthesis and complete phase diagram of FeSe$_{1-x}$S$_{x}$ $(0 \leq x \leq 1)$ single crystals

TL;DR

This study synthesizes FeSe$_{1-x}$S$_{x}$ single crystals across the full composition range, mapping their phase diagram and revealing the interplay between nematicity, superconductivity, and resistivity behavior.

Contribution

It provides the first complete phase diagram of FeSe$_{1-x}$S$_{x}$ single crystals, including high sulfur doping, and investigates the competition between resistivity upturns and superconductivity.

Findings

Superconducting dome appears within the nematic phase.

Resistivity upturn with characteristic temperature $T^*$ shows a dome-like dependence on $x$.

Normal state resistivity transitions from non-Fermi-liquid to Fermi-liquid behavior with S doping.

Abstract

We report the successful synthesis of FeSe$_{1-x}$S$_{x}$ single crystals with $x$ ranging from 0 to 1 via a hydrothermal method. A complete phase diagram of FeSe$_{1-x}$S$_{x}$ has been obtained based on resistivity and magnetization measurements. The nematicity is suppressed with increasing $x$, and a small superconducting dome appears within the nematic phase. Outside the nematic phase, the superconductivity is continuously suppressed and reaches a minimum $T_c$ at $x$ = 0.45; beyond this point, $T_c$ slowly increases until $x$ = 1. Intriguingly, an anomalous resistivity upturn with a characteristic temperature $T^*$ in the intermediate region of $0.31 \leq x \leq 0.71$ is observed. $T^{*}$ shows a dome-like behavior with a maximum value at $x$ = 0.45, which is opposite the evolution of $T_c$, indicating competition between $T^*$ and superconductivity. The origin of $T^*$ is discussed in detail. Furthermore, the normal state resistivity evolves from non-Fermi-liquid to Fermi-liquid behavior with S doping at low temperatures, accompanied by a reduction in electronic correlations. Our study addresses the lack of single crystals in the high-S doping region and provides a complete phase diagram, which will promote the study of relations among nematicity, superconductivity, and magnetism.