Tunable vortex Majorana zero modes in LiFeAs superconductor

TL;DR

This paper demonstrates that LiFeAs, a stoichiometric superconductor, hosts tunable vortex Majorana zero modes (MZMs), providing a promising platform for topological quantum computation through controllable manipulation of MZMs.

Contribution

The study shows that LiFeAs can host tunable MZMs influenced by native impurities, overcoming inhomogeneity issues in other FeSCs, and suggests electrostatic gating as a control method.

Findings

MZMs appear in vortices influenced by native impurities in LiFeAs.

Detailed analysis clarifies the emergence mechanism of MZMs in this material.

MZMs can be tuned by controllable methods like electrostatic gating.

Abstract

The recent realization of pristine Majorana zero modes (MZMs) in vortices of iron-based superconductors (FeSCs) provides a promising platform for long-sought-after fault-tolerant quantum computation. A large topological gap between the MZMs and the lowest excitations enabled detailed characterization of vortex MZMs in those materials. Despite those achievements, a practical implementation of topological quantum computation based on MZM braiding remains elusive in this new Majorana platform. Among the most pressing issues are the lack of controllable tuning methods for vortex MZMs and inhomogeneity of the FeSC Majorana compounds that destroys MZMs during the braiding process. Thus, the realization of tunable vortex MZMs in a truly homogeneous compound of stoichiometric composition and with a charge neutral cleavage surface is highly desirable. Here we demonstrate experimentally that the stoichiometric superconductor LiFeAs is a good candidate to overcome these two obstacles. Using scanning tunneling microscopy, we discover that the MZMs, which are absent on the natural surface, can appear in vortices influenced by native impurities. Our detailed analysis and model calculations clarify the mechanism of emergence of MZMs in this material, paving a way towards MZMs tunable by controllable methods such as electrostatic gating. The tunability of MZMs in this homogeneous material offers an unprecedented platform to manipulate and braid MZMs, the essential ingredients for topological quantum computation.