Terahertz single conductance quantum and topological phase transitions in topological insulator Bi2Se3 ultrathin films

In ambient conditions, the detection of topological surface states in topological insulators is impaired by the presence of bulk and quantum well states. Here, Park et al. demonstrate how such topological states in epitaxial ultrathin Bi2Se3 may be isolated using terahertz time-domain spectroscopy.