American Physical Society, Physical review B, 24(88)
DOI: 10.1103/physrevb.88.245122
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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. ; Comment: 5 pages