Dissipation-enabled fractional Josephson effect
D.C. Sticlet (Kavli institute of nanoscience Delft, TU Delft - QN/Akhmerov Group, National Institute for Research and Development of Isotopic and Molecular Technologies)
Jay D. Sau (University of Maryland)
A.R. Akhmerov (TU Delft - QN/Akhmerov Group, Kavli institute of nanoscience Delft)
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Abstract
The anomalous 4π-periodic ac Josephson effect, a hallmark of topological Josephson junctions, was experimentally observed in a quantum spin Hall insulator. This finding is unexpected due to time-reversal symmetry preventing the backscattering of the helical edge states and therefore suppressing the 4π-periodic component of the Josephson current. Here, we analyze the two-particle inelastic scattering as a possible explanation for this experimental finding. We show that a sufficiently strong inelastic scattering restores the 4π-periodic component of the current beyond the short Josephson junction regime. Its signature is an observable peak in the power spectrum of the junction at half the Josephson frequency. We propose to use the exponential dependence of the peak width on the applied bias and the magnitude of the dc current as means of verifying that the inelastic scattering is indeed the mechanism responsible for the 4π-periodic signal.