Hydrothermal synthesis and complete phase diagram of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">FeSe</mml:mi><mml:mrow><mml:mn>1</mml:mn><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:mrow></mml:msub><mml:msub><mml:mi mathvariant="normal">S</mml:mi><mml:mi>x</mml:mi></mml:msub><mml:mo> </mml:mo><mml:mrow><mml:mo>(</mml:mo><mml:mn>0</mml:mn><mml:mo>≤</mml:mo><mml:mi>x</mml:mi><mml:mo>≤</mml:mo><mml:mn>1</mml:mn><mml:mo>)</mml:mo></mml:mrow></mml:math> single crystals

Abstract

We report the successful synthesis of ${\mathrm{FeSe}}_{1\ensuremath{-}x}{\mathrm{S}}_{x}$ single crystals with $x$ ranging from 0 to 1 via a hydrothermal method. A complete phase diagram of ${\mathrm{FeSe}}_{1\ensuremath{-}x}{\mathrm{S}}_{x}$ 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 ${T}_{\text{c}}$ at $x$ = 0.45; beyond this point, ${T}_{\text{c}}$ slowly increases until $x$ = 1. Intriguingly, an anomalous resistivity upturn with a characteristic temperature ${T}^{*}$ in the intermediate region of $0.31\ensuremath{\le}x\ensuremath{\le}0.71$ is observed. ${T}^{*}$ shows a domelike behavior with a maximum value at $x$ = 0.45, which is opposite the evolution of ${T}_{\text{c}}$, 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.

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