Abnormal Surface Nonlinear Optical Responses in Topological Materials

Abstract

Nonlinear optical (NLO) responses of topological materials are under active research in recent years. Yet by far, most studies focused on the bulk properties, whereas the surface effects and the difference between surface and bulk responses have not been systematically studied. Here we develop a generic Green's function framework to investigate the surface NLO properties of topological materials. The Green's function framework can naturally incorporate many-body effects and can be easily extended to high-order NLO responses. Using Td-WTe2 as an example, we reveal that the surface can behave disparately from the bulk under light illumination. Remarkably, the shift and circular currents on the surface can flow in opposite directions to those in the bulk interior. Moreover, the light-induced spin current on the surface can be orders of magnitude stronger than its bulk counterpart. We also study the responses under inhomogeneous field and higher-order NLO effect, which are all distinct on the surface. These anomalous surface NLO responses suggest that light can be a valuable tool for probing the surface states of topological materials. On the other hand, the surface effects shall be prudently considered when investigating the optical properties of topological materials, especially if the material is of nanoscale and/or the light penetration depth is small.

17 pages, 5 figures

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• Topology and geometry under the nonlinear electromagnetic spotlight
• Nonlinear optical probe of tunable surface electrons on a topological insulator
• Optical detection and manipulation of spontaneous gyrotropic electronic order in a transition-metal dichalcogenide semimetal
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Cited by in corpus (6)

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• Linear photogalvanic effect in surface states of topological insulators
• Regularized lattice theory for spatially dispersive nonlinear optical conductivities
• Two-photon Interface of Nuclear Spins Based on the Opto-Nuclear Quadrupolar Effect
• Efficient Quantum Transduction Using Anti-Ferromagnetic Topological Insulators
• Quantum theory of nonlinear electromagnetic response