Experimental realization of a topological crystalline insulator in SnTe

Understand

Topological insulators materialize a topological quantum state of matter where unusual gapless metallic state protected by time-reversal symmetry appears at the edge or surface.

• Their discovery stimulated the search for new topological states protected by other symmetries, and a recent theory predicted the existence of "topological crystalline insulators" (TCIs) in which the metallic surface states are protected by mirror symmetry of the crystal.
• However, its experimental verification has not yet been reported.
• Here we show the first and definitive experimental evidence for the TCI phase in tin telluride (SnTe) which was recently predicted to be a TCI.