Piezostrain-induced in-plane anisotropy of superconducting transition temperature for FeSe0.5Te0.5 thin films

TL;DR

This study demonstrates that applying piezostrain to FeSe0.5Te0.5 thin films induces in-plane anisotropy of the superconducting transition temperature, revealing a novel strain-controlled anisotropic superconducting behavior.

Contribution

It is the first to show that piezostrain can induce in-plane Tc anisotropy in FeSe0.5Te0.5 thin films, linking strain to electronic nematicity and inhomogeneous superconductivity.

Findings

Piezostrain induces in-plane lattice parameter differences.

In-plane Tc anisotropy correlates with lattice parameter differences.

Extrinsic effects were ruled out, supporting intrinsic strain effects.

Abstract

Superconductivity is a macroscopic quantum phenomenon and it is commonly believed that the in-plane superconducting transition temperature (Tc) should be isotropic for superconductors with crystal structures of stacking layers (quasi two-dimensional). Here, we report the observation of piezostrain-induced in-plane anisotropy of Tc in FeSe0.5Te0.5 (FST) thin films grown on ferroelectrics. The as-prepared FST shows tetragonal phase with equal in-plane lattice parameters and absence of in-plane anisotropy of Tc. Upon applying electric fields, piezostrain induces difference of the in-plane lattice parameters (a-b) and in-plane anisotropy of Tc. The in-plane anisotropy of Tc correlates with a-b and becomes more remarkable for larger values of a-b. Some possible extrinsic effects were ruled out by experiments and analysis. It is suggested that electronic nematicity with one direction induced by piezostrain and inhomogeneous superconductivity in FST are involved in this unusual phenomenon. This work reveals the exotic behavior of FST and will stimulate exploration of similar behavior in other unconventional superconductors.