From frustrated magnetism to spontaneous Chern insulators

TL;DR

This paper investigates how electrons interacting with a chiral magnetic background can give rise to topologically non-trivial band structures, including Chern insulators, influenced by temperature and external magnetic fields.

Contribution

It demonstrates the emergence of Chern insulators from classical magnetic backgrounds with scalar chirality, and shows tunability of topological phases via external magnetic fields.

Findings

Identification of topological transitions as a function of Fermi energy and temperature.

Realization of a tunable Chern insulator with reversible chiral edge modes.

Demonstration of magnetic field control over topological states.

Abstract

We study the behaviour of electrons interacting with a classical magnetic background via a strong Hund coupling. The magnetic background results from a Hamiltonian which favours at low temperature the emergence of a phase with non-zero scalar chirality. The strong Hund's coupling combined with the total chirality of the classical spins induces in the electrons an effective flux which results in the realisation of a band structure with non zero Chern number. First, we consider as a magnetic background a classical spin system with spontaneous net chirality. We study the Density of States (DoS) and Hall conductance in order to analyse the topological transitions, as a function of the Fermi energy and the temperature of the classical spins. We also study a similar model in which the Chern number of the filled bands can be "tuned" with the external magnetic field, resulting in a topological insulator in which the direction of the chiral edge mode can be reverted by reversing the orientantion of the magnetic field applied to the classical magnetic system.