Time-Reversal-Invariant Z4 Fractional Josephson Effect

Fan Zhang and C. L. Kane
Phys. Rev. Lett. 113, 036401 – Published 14 July 2014

Abstract

We study the Josephson junction mediated by the quantum spin Hall edge states and show that electron-electron interactions lead to a dissipationless fractional Josephson effect in the presence of time-reversal symmetry. Surprisingly, the periodicity is 8π, corresponding to a Josephson frequency eV/2. We estimate the magnitude of interaction-induced many-body level splitting responsible for this effect and argue that it can be measured by using tunneling spectroscopy. For strong interactions we show that the Josephson effect is associated with the weak tunneling of charge e/2 quasiparticles between the superconductors. Our theory describes a fourfold ground state degeneracy that is similar to that of coupled “fractional” Majorana modes but is protected by time-reversal symmetry.

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  • Received 5 April 2014

DOI:https://doi.org/10.1103/PhysRevLett.113.036401

© 2014 American Physical Society

Authors & Affiliations

Fan Zhang and C. L. Kane

  • Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

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Issue

Vol. 113, Iss. 3 — 18 July 2014

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