Majorana corner states on the dice lattice

TL;DR

This paper demonstrates that flat bands with a high Chern number in the dice lattice can host second-order topological superconductivity, featuring Majorana corner states, thus offering a new platform for exotic topological phases.

Contribution

It reveals that flat bands with Chern number ±2 in the dice lattice can induce a second-order topological superconductor with Majorana corner states, linking normal state topology to Majorana localization.

Findings

Majorana bound states appear at lattice corners.

Superconducting state exhibits second-order topological phase.

Flat bands with high Chern number can host topological superconductivity.

Abstract

Lattice geometry continues providing exotic topological phases in condensed matter physics. Exciting recent examples are the higher-order topological phases, manifesting via localized lower-dimensional boundary states. Moreover, flat electronic bands with a non-trivial topology arise in various lattices and can hold a finite superfluid density, bounded by the Chern number $C$. Here we consider attractive interaction in the dice lattice that hosts flat bands with $C=\pm2$ and show that the induced superconducting state exhibits a second-order topological phase with mixed singlet-triplet pairing. The second-order nature of the topological superconducting phase is revealed by the zero-energy Majorana bound states at the lattice corners. Hence, the topology of the normal state dictates the nature of the Majorana localization. These findings suggest that flat bands with a higher Chern number provide feasible platforms for inducing higher-order topological superconductivity.