Observation of Floquet-Bloch states on the surface of a topological insulator

• DOI: 10.1364/up.2014.10.thu.a.2
• Publication Date: 2014-07-11T15:47:14Z
• Authors: Y. H. Wang; H. Steinberg; P. Jarillo-Herrero; N. Gedik
• Keywords: Topological insulator; Floquet theory; Surface States

The unique electronic properties of the surface electrons in a topological insulator [1] are protected by time-reversal symmetry. Circularly polarized light naturally breaks symmetry, which may lead to an exotic quantum Hall state [2]. Using time- and angle-resolved photoemission spectroscopy [3] [4], we show that intense ultrashort mid-infrared pulse with energy below bulk band gap hybridizes Dirac fermions form Floquet-Bloch bands when pump is present [Fig. 1] [5]. These photon dressed exhibit polarization-dependent gaps at avoided crossings 2A B]. photons induce additional point 2C], signature broken symmetry on surface. size consistent calculation based theory [6]. This results Chern as originally proposed Haldane [7]. observations establish solids pave way for optical manipulation states matter.