Corner- and sublattice-sensitive Majorana zero modes on the kagome lattice

TL;DR

This paper explores how sublattice terminations on the kagome lattice influence boundary states and demonstrates methods to realize controllable Majorana zero modes and Kramers pairs in topological superconductors.

Contribution

It reveals the impact of sublattice termination on boundary physics and proposes new platforms for controllable Majorana zero modes in kagome topological insulators.

Findings

Sublattice termination affects Dirac point energies of edge states.

Realization of second-order topological superconductors with Majorana Kramers pairs.

Controllable Majorana zero modes with s-wave superconductors and Zeeman field.

Abstract

In a first-order topological phase with sublattice degrees of freedom, a change in the boundary sublattice termination has no effect on the existence of gapless boundary states in dimensions higher than one. However, such a change may strongly affect the physical properties of those boundary states. Motivated by this observation, we perform a systematic study of the impact of sublattice terminations on the boundary physics on the two-dimensional kagome lattice. We find that the energies of the Dirac points of helical edge states in two-dimensional first-order topological kagome insulators sensitively depend on the terminating sublattices at the edge. Remarkably, this property admits the realization of a time-reversal invariant second-order topological superconducting phase with highly controllable Majorana Kramers pairs at the corners and sublattice domain walls by putting the topological kagome insulator in proximity to a $d$-wave superconductor. Moreover, substituting the $d$-wave superconductor with a conventional $s$-wave superconductor, we find that highly controllable Majorana zero modes can also be realized at the corners and sublattice domain walls if an in-plane Zeeman field is additionally applied. Our study reveals promising platforms to implement highly controllable Majorana zero modes.