Ultrafast and Local Optoelectronic Transport in Topological Insulators

Recently, topological insulators (TIs) were discovered as a new class of materials representing a subset of topological quantum matter. While a TI possesses a bulk band gap similar to an ordinary insulator, it exhibits gapless states at the surface featuring a spin-helical Dirac dispersion. Due to this unique surface band structure, TIs may find use in (opto)spintronic applications. Herein, optoelectronic methods are discussed to characterize, control, and read-out surface state charge and spin transport of 3D TIs. In particular, time- and spatially-resolved photocurrent microscopy at near-infrared excitation can give fundamental insights into charge carrier dynamics, local electronic properties, and the interplay between bulk and surface currents. Furthermore, possibilities of applying such ultrafast optoelectronic methods to study Berry curvature-related transport phenomena in topological semimetals are discussed.