Growth of superconducting epitaxial films of sulfur substituted FeSe via pulsed laser deposition

TL;DR

This study successfully grew epitaxial FeSe$_{1-x}$S$_x$ thin films via pulsed laser deposition, revealing that nematic order suppression does not universally enhance superconductivity, contrasting with FeSe$_{1-y}$Te$_y$ behavior.

Contribution

First demonstration of epitaxial FeSe$_{1-x}$S$_x$ films showing systematic nematic and superconducting transition changes with sulfur content.

Findings

Nematic transition temperature decreases with S content.

Superconducting transition temperature gradually decreases with S content.

A new magnetic transition anomaly appears at high S content.

Abstract

We report the successful growth of epitaxial thin films of FeSe$_{1-x}$S$_x$ with $x \leq 0.43$ via pulsed laser deposition. As S content increases, the nematic transition temperature, $T_{\mathrm s}$, decreases systematically and the superconducting transition temperature, $T_{\mathrm c}$, shows a gradual decrease even when $x$ exceeds the nematic end point (NEP), similar to bulk samples. A new kink anomaly was observed in the $\rho$-$T$ curves for films with large $x$, which is likely due to a magnetic transition. The obtained phase diagram of FeSe$_{1-x}$S$_x$ thin films is in contrast to that of FeSe$_{1-y}$Te$_y$ films, which shows a rapid increase of $T_{\mathrm c}$ at the NEP. Our results demonstrate that the relation between the nematic order and the superconductivity is not universal in the FeSe system, suggesting that the nematic transition does not play a primary role in the superconductivity in these materials.