Ordered and tunable Majorana-zero-mode lattice in naturally strained LiFeAs

TL;DR

This paper demonstrates the creation of an ordered, tunable lattice of Majorana zero modes in naturally strained LiFeAs, providing a promising platform for topological quantum computing with controllable vortex arrangements.

Contribution

It reports the discovery of an ordered, tunable MZM lattice in LiFeAs, overcoming disorder issues in previous materials, and shows MZM coupling at reduced vortex spacing.

Findings

Over 90% of vortices are topological MZMs.

Vortex lattice is ordered and tunable by magnetic field.

MZMs couple as vortex spacing decreases.

Abstract

Majorana zero modes (MZMs) obey non-Abelian statistics and are considered building blocks for constructing topological qubits. Iron-based superconductors with topological band structures have emerged as promising hosting materials, since isolated candidate MZMs in the quantum limit have been observed inside the topological vortex cores. However, these materials suffer from issues related to alloying-induced disorder, uncontrolled vortex lattices and a low yield of topological vortices. Here, we report the formation of an ordered and tunable MZM lattice in naturally-strained stoichiometric LiFeAs by scanning tunneling microscopy/spectroscopy (STM/S). We observe biaxial charge density wave (CDW) stripes along the Fe-Fe and As-As directions in the strained regions. The vortices are pinned on the CDW stripes in the As-As direction and form an ordered lattice. We detect more than 90 percent of the vortices to be topological and possess the characteristics of isolated MZMs at the vortex center, forming an ordered MZM lattice with the density and the geometry tunable by an external magnetic field. Remarkably, with decreasing the spacing of neighboring vortices, the MZMs start to couple with each other. Our findings provide a new pathway towards tunable and ordered MZM lattices as a platform for future topological quantum computation.