Fe$_{1+y}$Te$_{x}$Se$_{1-x}$: a delicate and tunable Majorana material

TL;DR

This study reveals the presence of topological band inversion in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$, showing it as a tunable Majorana material where excess Fe inhibits topological phases, and strain or doping can induce phase transitions.

Contribution

It demonstrates the impact of excess Fe on topological properties and proposes a tunable topological phase in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$ based on detailed spectroscopic analysis.

Findings

Observation of band inversion in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$

Excess Fe inhibits topological phase transition

Potential to tune topological phase via strain or doping

Abstract

We report the observation for the p$_{z}$ electron band and the band inversion in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$ with angle-resolved photoemission spectroscopy. Furthermore, we found that excess Fe (y>0) inhibits the topological band inversion in Fe$_{1+y}$Te$_{x}$Se$_{1-x}$, which explains the absence of Majorana zero modes in previous reports for Fe$_{1+y}$Te$_{x}$Se$_{1-x}$ with excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.