Floquet Engineering of Magnetism in Topological Insulator Thin Films

TL;DR

This paper demonstrates how circularly polarized light can dynamically control magnetism in topological insulator thin films, inducing phase transitions and revealing non-equilibrium magnetic behaviors.

Contribution

It introduces a Floquet engineering method to manipulate magnetism in topological materials using light, highlighting non-equilibrium effects and phase transitions beyond equilibrium conditions.

Findings

Magnetic phase transition from ferromagnetism to paramagnetism under light

Non-equilibrium Curie temperatures depend on time scale and setup

Magnetism and topology are decoupled in non-equilibrium regimes

Abstract

Dynamic manipulation of magnetism in topological materials is demonstrated here via a Floquet engineering approach using circularly polarized light. Increasing the strength of the laser field, besides the expected topological phase transition, the magnetically doped topological insulator thin film also undergoes a magnetic phase transition from ferromagnetism to paramagnetism, whose critical behavior strongly depends on the quantum quenching. In sharp contrast to the equilibrium case, the non-equilibrium Curie temperatures vary for different time scale and experimental setup, not all relying on change of topology. Our discoveries deepen the understanding of the relationship between topology and magnetism in the non-equilibrium regime and extend optoelectronic device applications to topological materials.