Condensed Matter Seminar: Z4 Parafermions in an interacting quantum spin Hall Josephson junction coupled to an impurity spin

Yuval Vinkler, Free University Berlin

15 January 2018, 11:00 
Kaplun Building, Flekser Hall 118 
Condensed Matter Seminar


Z4 parafermions can be realized in a strongly interacting quantum spin Hall Josephson junction or in a spin Hall Josephson junction strongly coupled to an impurity spin. In this talk I will present a system that has both features, but with weak (repulsive) interactions and a weakly coupled spin. I will show that for a strongly anisotropic exchange interaction, at low temperatures the system enters a strong coupling limit in which it hosts two Z4 parafermions, characterizing a fourfold degeneracy of the ground state. The parafermion operators can be constructed explicitly, and I will show that they facilitate fractional e/2 charge tunneling across the junction. The dependence of the effective low-energy spectrum on the superconducting phase difference reveals an 8π periodicity of the supercurrent.



Event Organizer: Prof. Eran Sela

Tel Aviv University, P.O. Box 39040, Tel Aviv 6997801, Israel
UI/UX Basch_Interactive