Insight into Topological Insulators from Infrared Spectroscopy

Topological insulators are certain band-insulator compounds that exhibit a new phase of quantum matter with inverted insolating energy gap. As a result, these bulk insulators have conducting states on the surface. This new state of matter is a consequence of strong spin-orbit coupling in these materials. We use infrared reflectance spectroscopy to probe electrodynamics of charge carriers at different temperatures and we conduct magneto-optical spectroscopy experiments to probe magneto-electric coupling. We present findings on several second-generation Bi-based topological insulators at temperatures ranging from 10 to 300 K and in magnetic fields up to 18 T. In addition, we discuss the charge inhomogeneities in these novel materials.