Orbital magnetization of Floquet topological systems

TL;DR

This paper derives a comprehensive formula for the orbital magnetization in Floquet systems, revealing significant magnetization in various topological phases and occupation scenarios, including thermal and quench states.

Contribution

It provides the first general expression for orbital magnetization in Floquet systems applicable to any driving protocol and occupation, highlighting effects beyond Chern number predictions.

Findings

Orbital magnetization is large in both Chern insulators and anomalous phases.

Magnetization is significant for thermal and quenched occupations.

Highly sensitive to van Hove singularities in Floquet bands.

Abstract

A general expression for the orbital magnetization of a Floquet system is derived. The expression holds for a clean system, and is valid for any driving protocol, and arbitrary occupation of the bands. The orbital magnetization is shown to be large not only for Chern insulators, but also for anomalous phases where the Chern number does not fully account for the topology. In addition, the orbital magnetization is shown to take significant values both for a thermal equilibrium occupation of the Floquet bands, and for occupations determined by a quantum quench from an initial state with zero orbital magnetization. For the latter case, the orbital magnetization is shown to be highly sensitive to van Hove singularities of the Floquet bands.