Coexistence of superconductivity and magnetism in K0.8Fe2Se1.4S0.4

TL;DR

This study synthesizes high-quality K0.8Fe2Se1.4S0.4 crystals, revealing that superconductivity coexists with magnetism, with S substitution not suppressing Tc and indicating complex interplay between chemical doping and magnetic fluctuations.

Contribution

It demonstrates the coexistence of superconductivity and magnetism in K0.8Fe2Se1.4S0.4, highlighting the role of S substitution in modulating electronic properties without suppressing Tc.

Findings

Superconducting transition at ~32.8 K

Coexistence of superconductivity and magnetism confirmed by ESR

S substitution does not suppress Tc, unlike pressure effects

Abstract

High-quality single crystals of K0.8Fe2Se1.4S0.4 are successfully synthesized by self-flux method with the superconducting transition temperatures Tconset = 32.8 K and Tczero = 31.2 K. In contrast to external pressure effect on superconductivity, the substitution of S for Se does not suppress Tc, which suggests that chemical doping may mainly modulate the anion height from Fe-layer rather than compressing interlayer distance. The investigation of the micromagnetism by electron spin resonance shows clear evidence for strong spin fluctuation at temperatures above Tc. Accompanied by the superconducting feature spectra, a novel resonance signal develops gradually upon cooling below Tc, indicating the coexistence of superconductivity and magnetism in K0.8Fe2Se1.4S0.4 crystal.