A symmetry-respecting topologically-ordered surface phase of 3d electron topological insulators

Understand

A 3d electron topological insulator (ETI) is a phase of matter protected by particle-number conservation and time-reversal symmetry.

• It was previously believed that the surface of an ETI must be gapless unless one of these symmetries is broken.
• A well-known symmetry-preserving, gapless surface termination of an ETI supports an odd number of Dirac cones.
• In this paper we deduce a symmetry-respecting, gapped surface termination of an ETI, which carries an intrinsic 2d topological order, Moore-Read x anti-semion.