Details

Autor(en) / Beteiligte

• Wang, Y. H.
• Steinberg, H.
• Jarillo-Herrero, P.
• Gedik, N.

Titel

Observation of Floquet-Bloch States on the Surface of a Topological Insulator

Ist Teil von

• Science (American Association for the Advancement of Science), 2013-10, Vol.342 (6157), p.453-457

Ort / Verlag

Washington, DC: American Association for the Advancement of Science

Erscheinungsjahr

2013

Link zum Volltext

Quelle

American Association for the Advancement of Science

Beschreibungen/Notizen

• 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.