Condensed Matter Seminar: Fractionalizing a helical liquid

Abstract:

Helical one-dimensional liquids occur for instance as edge states of two-dimensional topological insulators. These edge states are protected by time-reversal symmetry and particle number conservation. At interfaces between domains gapped by ferromagnetic and superconducting coating, non-abelian Majorana bound states have been predicted to emerge. In this talk, a generalization to a time-reversal symmetric setup is discussed, in which the magnetic domains are replaced by regions subject to a Mott-like gap. We show that this scenario can naturally arise in sufficiently strongly interacting topological insulators with spin-orbit coupling. The interfaces between superconducting and Mott-like domains can now be understood as binding Z4 parafermions, which encode an enlarged ground state degeneracy. This allows for the manipulation of charge in units of e/2, heralded by an 8-pi Josephson effect, permits non-ablian braidings, and does not require the coexistence of superconductivity and magnetic fields.

Seminar Organizer: Dr. Eran Sela