Special CPM Seminar

Building fractional topological insulators

Fiona Burnell

Subdepartment of Theoretical Physics & All Souls College
University of Oxford

Time-reversal invariant band insulators can be separated into two categories: ‘ordinary’ insulators and ‘topological’ insulators. Topological band insulators have low-energy edge modes that cannot be gapped without violating time-reversal symmetry, while ordinary insulators do not. A natural question is whether more exotic time- reversal invariant insulators (insulators not connected adiabatically to band insulators) can also exhibit time-reversal protected edge modes. In 2 dimensions, one example of this is the fractional spin Hall insulator (essentially a spin-up and spin-down copy of a fractional quantum Hall insulator, with opposite effective magnetic fields for each spin). I will discuss another family of strongly interacting insulators, which exist in both 2 and 3 dimensions, that can have time-reversal protected edge modes. This gives a new set of examples of ‘fractional’ topological insulators.