Observation of Floquet-Bloch States on the Surface of a Topological Insulator
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Author(s)
Wang, Y. H.
Steinberg, Hadar
Jarillo-Herrero, Pablo
Gedik, Nuh
Date Issued
October 2013
Journal
Science
Citation
Wang, Y. H., H. Steinberg, P. Jarillo-Herrero, and N. Gedik. “Observation of Floquet-Bloch States on the Surface of a Topological Insulator.” Science 342, no. 6157 (October 25, 2013): 453–457.
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Author's final manuscript
Abstract
The unique electronic properties of the surface electrons in a topological insulator are protected by time-reversal symmetry. Circularly polarized light naturally breaks time-reversal symmetry, which may lead to an exotic surface quantum Hall state. Using time- and angle-resolved photoemission spectroscopy, we show that an intense ultrashort midinfrared pulse with energy below the bulk band gap hybridizes with the surface Dirac fermions of a topological insulator to form Floquet-Bloch bands. These photon-dressed surface bands exhibit polarization-dependent band gaps at avoided crossings. Circularly polarized photons induce an additional gap at the Dirac point, which is a signature of broken time-reversal symmetry on the surface. These observations establish the Floquet-Bloch bands in solids and pave the way for optical manipulation of topological quantum states of matter.
MIT Department
Massachusetts Institute of Technology. Department of Physics
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DOI of Published Version
https://doi.org/10.1126/science.1239834
