Suppression of phase separation and giant enhancement of superconducting transition temperature in FeSe${}_{1-x}$Te${}_x$ thin films

Abstract

We demonstrate the successful fabrication on CaF${}_2$ substrates of FeSe${}_{1-x}$Te${}_x$ films with $0\le x\le 1$, including the region of $0.1\le x\le 0.4$, which is well known to be the "phase-separation region", via pulsed laser deposition which is a thermodynamically non-equilibrium method. In the resulting films, we observe a giant enhancement of the superconducting transition temperature, $T_{\mathrm{c}}$, in the region of $0.1\le x\le 0.4$: the maximum value reaches 23 K, which is approximately 1.5 times as large as the values reported for bulk samples of FeSe${}_{1-x}$Te${}_x$. We present a complete phase diagram of FeSe${}_{1-x}$Te${}_x$ films. Surprisingly, a sudden suppression of $T_{\mathrm{c}}$ is observed at $0.1<x<0.2$, while $T_{\mathrm{c}}$ increases with decreasing $x$ for $0.2\le x<1$. Namely, there is a clear difference between superconductivity realized in $x=0-0.1$ and in $x\ge 0.2$. To obtain a film of FeSe${}_{1-x}$Te${}_x$ with high $T_{\mathrm{c}}$, the controls of the Te content $x$ and the in-plane lattice strain are found to be key factors.

Accepted for publication in Proc. Natl. Acad. Sci. USA

References in corpus (8)

• Superconductivity close to magnetic instability in Fe(Se1-xTex)0.82
• Effect of Structural Parameters on Superconductivity in Fluorine-Free LnFeAsO1-y (Ln=La,Nd)
• First-order magnetic and structural phase transitions in Fe${}_{1+y}$Se${}_x$Te${}_{1-x}$
• The Structural Phase Transition in FeSe (Fe1+dSe)
• Systematic Comparison of Eight Substrates in the Growth of FeSe${}_{0.5}$Te${}_{0.5}$ Superconducting Thin Films
• Epitaxial growth of FeSe${}_{0.5}$Te${}_{0.5}$ thin films on CaF${}_2$ substrates with high critical current density
• Superconductivity in the PbO-type Structure alpha-FeSe
• Enhancement of Transition Temperature in FexSe0.5Te0.5 Film via Iron Vacancies

Cited by in corpus (11)

• Exotic Superconducting States in FeSe-based Materials
• Influence of interstitial Fe to the phase diagram of Fe${}_{1+y}$Te${}_{1-x}$Se${}_x$ single crystals
• Hybrid symmetry epitaxy of superconducting Fe(Te,Se) film on a topological insulator
• Phase diagrams on composition-spread Fe${}_y$Te${}_{1-x}$Se${}_x$ films
• Electronic transport properties and hydrostatic pressure effect of FeSe${}_{0.67}$Te${}_{0.33}$ single crystals free of phase separation
• The influence of the in-plane lattice constant on the superconducting transition temperature of FeSe0.7Te0.3 thin films
• Investigation of Transport Properties for FeSe${}_{1-x}$Te${}_x$ Thin Films under Magnetic Fields
• Fabrication of tetragonal FeSe - FeS alloy films with high sulfur contents by alternate deposition
• Superconducting four-fold Fe(Te,Se) film on six-fold magnetic MnTe via hybrid symmetry epitaxy
• Superconducting fluctuations in FeSe${}_{0.5}$Te${}_{0.5}$ thin films probed via microwave spectroscopy
• Novel method to study strain effect of thin films using a piezoelectric-based device and a flexible metallic substrate