Nonlinear Magneto-Optical and Magnetoelectric Phenomena in Topological Insulator Heterostructures

TL;DR

This paper explores nonlinear magneto-optical and magnetoelectric effects in topological insulator heterostructures, revealing how electric fields induce polarization and modulate Hall currents beyond linear response, with topological protection at low frequencies.

Contribution

It uncovers nonlinear phenomena in topological insulator films, demonstrating electric field-induced polarization and Hall current modulation controlled by second-order susceptibility.

Findings

Electric fields induce perpendicular AC polarization.

Circularly polarized waves induce static polarization.

Hall current modulation depends on second-order susceptibility.

Abstract

Three-dimensional topological insulator films in contact with magnetic layers exhibit intriguing magneto-optical and magnetoelectric phenomena, but little is known beyond the linear response regime. We demonstrate that the presence of two electric fields parallel to the surface of the film induces a perpendicular AC polarization, whereas a static polarization can be induced by applying a single circularly polarized electromagnetic wave. These phenomena are determined by the second-order susceptibility, which also controls the manner in which the anomalous Hall current is modulated by a perpendicular AC electric field. If the modulation frequency is low, the Hall effect is topologically protected and the nonlinear response vanishes.