Topological Superconductivity in Altermagnetic Heterostructures on a Honeycomb Lattice

TL;DR

This paper explores how the lattice structure in altermagnet-superconductor heterostructures influences topological superconductivity, revealing a complex phase diagram with chiral and Majorana corner modes on a honeycomb lattice.

Contribution

It introduces a model on a honeycomb lattice showing the dependence of topological states on lattice structure and analyzes the robustness of these states under disorder.

Findings

Topological phases include chiral edge modes and Majorana corner modes.

Edge modes are robust to disorder, but corner modes are sensitive to microscopic details.

Vacancies can create low-energy states that mimic corner modes.

Abstract

Altermagnet-superconductor heterostructures have been shown, in principle, to provide a route towards realising topological superconductivity, and therefore host topologically protected boundary states. In this work we demonstrate that the topological states observed are dependent on the structure of the underlying lattice. By deriving and analysing a model on a honeycomb lattice, we demonstrate that the topological phase diagram has a rich structure containing both chiral edge modes and Majorana corner modes, the latter of which are an indication of higher-order topology. We analyse the effect of disorder on these states and find that whilst the edge modes are robust to a disordered system, any potential observation of the corner modes may be sensitive to the microscopic details. In particular, we show that vacancies can lead to other low energy bound states that may be difficult to distinguish from the corner modes.