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arXiv · 1101.1541

Nonlinear optical probe of tunable surface electrons on a topological insulator

D. Hsieh·J. W. McIver·D. H. Torchinsky·D. R. Gardner·Y. S. Lee·N. Gedik
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Abstract

We use ultrafast laser pulses to experimentally demonstrate that the second-order optical response of bulk single crystals of the topological insulator Bi$_2$Se$_3$ is sensitive to its surface electrons. By performing surface doping dependence measurements as a function of photon polarization and sample orientation we show that second harmonic generation can simultaneously probe both the surface crystalline structure and the surface charge of Bi$_2$Se$_3$. Furthermore, we find that second harmonic generation using circularly polarized photons reveals the time-reversal symmetry properties of the system and is surprisingly robust against surface charging, which makes it a promising tool for spectroscopic studies of topological surfaces and buried interfaces.

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D. Hsieh, J. W. McIver, D. H. Torchinsky, D. R. Gardner, Y. S. Lee, N. Gedik. 2011-01-07. Nonlinear optical probe of tunable surface electrons on a topological insulator. https://doi.org/10.1103/physrevlett.106.057401

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