Experimental Confirmation and Characterization of Topological Insulators

Angle resolved photoelectron spectroscopy (ARPES) can be utilized to verify the existence and investigate the properties of topological insulators (TIs). The most important traits of TIs (existence of bulk gaps and odd number of surface state Fermi level crossings) have been verified for various TIs, providing the first and most direct evidence for TIs. Spin resolved ARPES confirmed the helical spin structures in surface states and gave solid evidence for the existence of TIs. We further describe recent studies on the quasi-particle dynamics in the topological metallic states and massive Dirac Fermions (opening of a gap at the Dirac point) due to time reversal symmetry breaking by magnetic impurities.