Observation of a large-gap topological-insulator class with a single Dirac cone on the surface

Topological insulators are exotic states of matter that show quantum-Hall-like behaviour in the absence of a magnetic field. Surface states in such systems are protected against scattering and are thought to provide an avenue for the realization of fault-tolerant quantum computing. Experiments now reveal the observation of such a topological state of matter in Bi2Se3, a naturally occurring stoichiometric material with a simple surface-state structure and a bulk energy gap larger than kBT at room temperature. Recent experiments and theories have suggested that strong spin–orbit coupling effects in certain band insulators can give rise to a new phase of quantum matter, the so-called topological insulator, which can show macroscopic quantum-entanglement effects1,2,3,4,5,6,7. Such systems feature two-dimensional surface states whose electrodynamic properties are described not by the conventional Maxwell equations but rather by an attached axion field, originally proposed to describe interacting quarks8,9,10,11,12,13,14,15. It has been proposed that a topological insulator2 with a single Dirac cone interfaced with a superconductor can form the most elementary unit for performing fault-tolerant quantum computation14. Here we present an angle-resolved photoemission spectroscopy study that reveals the first observation of such a topological state of matter featuring a single surface Dirac cone realized in the naturally occurring Bi2Se3 class of materials. Our results, supported by our theoretical calculations, demonstrate that undoped Bi2Se3 can serve as the parent matrix compound for the long-sought topological device where in-plane carrier transport would have a purely quantum topological origin. Our study further suggests that the undoped compound reached via n-to-p doping should show topological transport phenomena even at room temperature.