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

Abstract

We report the successful growth of epitaxial thin films of FeSe${}_{1-x}$S${}_x$ with $x\le 0.43$ 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.