Light-induced topological magnons in two-dimensional van der Waals magnets

SciPost Phys 9,4, 061 (2020)

Light-induced topological magnons in two-dimensional van der Waals magnets

Emil Viñas Boström, Martin Claassen, James W. McIver, Gregor Jotzu, Angel Rubio, Michael A. Sentef

Driving a two-dimensional Mott insulator with circularly polarized light breaks time-reversal and inversion symmetry, which induces an optically-tunable synthetic scalar spin chirality interaction in the effective low-energy spin Hamiltonian. Here, we show that this mechanism can stabilize topological magnon excitations in honeycomb ferromagnets such as CrI 3 and in optical lattices. We find that the irradiated quantum magnet is described by a Haldane model for magnons that hosts topologically-protected edge modes. We study the evolution of the magnon spectrum in the Floquet regime and via time propagation of the magnon Hamiltonian for a slowly varying pulse envelope. Compared to similar but conceptually distinct driving schemes based on the Aharanov-Casher effect, the dimensionless light-matter coupling parameter λ=eEa/ℏω at fixed electric field strength is enhanced by a factor ∼10 5 . This increase of the coupling parameter allows to induce a topological gap of the order of Δ≈2 meV with realistic laser pulses, bringing an experimental realization of light-induced topological magnon edge states within reach.

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We acknowledge inspiring discussions with Abhisek Kole, Jin Zhang, Lede Xian and Claudio Verdozzi. We acknowledge support by the Max Planck Institute - New York City Center for Non-Equilibrium Quantum Phenomena. MAS acknowledges support by the DFG through the Emmy Noether programme (SE 558/2-1). This work was supported by the European Research Council (ERC-2015-AdG694097), the Cluster of Excellence Advanced Imaging of Matter (AIM), and Grupos Consolidados (IT1249-19). The Flatiron Institute is a Division of the Simons Foundation.

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