Observation of Floquet-Bloch States on the Surface of a Topological Insulator
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.
- Publication:
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Science
- Pub Date:
- October 2013
- DOI:
- arXiv:
- arXiv:1310.7563
- Bibcode:
- 2013Sci...342..453W
- Keywords:
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- PHYSICS Physics, Chemistry, Applied-Physics;
- Condensed Matter - Mesoscale and Nanoscale Physics
- E-Print:
- 23 pages including supplementary materials