First and Second Order Topological Phases on Ferromagnetic Breathing Kagome Lattice

TL;DR

This paper explores the rich topological phases in a ferromagnetic breathing kagome lattice, revealing multiple first and second order phases, their coexistence, and associated edge and corner states, with implications for thermal Hall effects.

Contribution

It is the first detailed study showing coexistence of first and second order topological phases in a breathing kagome lattice with Dzyaloshinskii-Moriya interaction.

Findings

Multiple first and second order topological phases identified.

Distinct phases characterized by different Chern numbers and edge states.

Observation of corner states and bulk-corner correspondence violations.

Abstract

In this work, topological properties of a ferromagnetic Heisenberg model on a breathing kagome lattice are investigated extensively in the presence of Dzyaloshinskii-Moriya interaction. While the kagome ferromagnet hosts only a single first order topological phase, the breathing kagome system exhibits multiple first and second order topological phases along with their coexistence. Magnon dispersion relation is obtained by using linear spin wave theory. Flat band and Dirac cones are obtained in the absence of Dzyaloshinskii-Moriya interaction. A topological phase diagram is presented where several first and second order phases as well as their overlap are identified. Values of thermal Hall conductivity for all the first order phases are obtained. Distinct first order phases are characterized by different sets of Chern numbers in association with the necessary chiral edge states in accordance to the first order bulk-boundary-correspondence rule. Second order phase is characterized by polarization along with the emergence of corner states. Violation of the second order bulk-corner-correspondence rule has been noted in some regions.