Hybrid symmetry epitaxy of superconducting Fe(Te,Se) film on a topological insulator

TL;DR

This paper introduces a novel hybrid symmetry epitaxy method enabling the growth of superconducting Fe(Te,Se) films on topological insulators, leading to stable superconductivity and new heterostructure possibilities.

Contribution

It demonstrates a new growth mode called hybrid symmetry epitaxy, allowing epitaxial growth of Fe(Te,Se) on Bi2Te3 despite lattice mismatch, and explores its superconducting properties and phase diagram.

Findings

Superconductivity with TC up to 13 K achieved in Fe(Te,Se)/Bi2Te3 heterostructure.

Superconductivity persists in Te-rich phase with low Se content (x=0.03).

Unique phase diagram differing from conventional Fe(Te,Se) systems.

Abstract

It is challenging to grow an epitaxial four-fold compound superconductor (SC) on six-fold topological insulator (TI) platform due to stringent lattice-matching requirement. Here, we demonstrate that Fe(Te,Se) can grow epitaxially on a TI (Bi2Te3) layer due to accidental, uniaxial lattice match, which is dubbed as "hybrid symmetry epitaxy". This new growth mode is critical to stabilizing robust superconductivity with TC as high as 13 K. Furthermore, the superconductivity in this FeTe1-xSex/Bi2Te3 system survives in Te-rich phase with Se content as low as x = 0.03 but vanishes at Se content above x = 0.56, exhibiting a phase diagram that is quite different from that of the conventional Fe(Te,Se) systems. This unique heterostructure platform that can be formed in both TI-on-SC and SC-on-TI sequences opens a route to unprecedented topological heterostructures.