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arXiv · 1705.06450

Missing Shapiro steps and the $8π$-periodic Josephson effect in interacting helical electron systems

Christopher J. Pedder·Tobias Meng·Rakesh Tiwari·Thomas L. Schmidt
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Abstract

Two-particle backscattering in time-reversal invariant interacting helical electron systems can lead to the formation of quasiparticles with charge $e/2$. We propose a way to detect such states by means of the Josephson effect in the presence of proximity-induced superconductivity. In this case, the existence of $e/2$ charges leads to an $8 π$-periodic component of the Josephson current which can be identified through measurement of Shapiro steps in Josephson junctions. In particular, we show that even when there is weak explicit time-reversal symmetry breaking, which causes the two-particle backscattering to be a sub-leading effect at low energies, its presence can still be detected in driven, current-biased Shapiro step measurements. The disappearance of some of these steps as a function of the drive frequency is directly related to the existence of non-Abelian zero-energy states. We suggest that this effect can be measured in current state-of-the-art Rashba wires.

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Christopher J. Pedder, Tobias Meng, Rakesh Tiwari, Thomas L. Schmidt. 2017-05-22. Missing Shapiro steps and the $8π$-periodic Josephson effect in interacting helical electron systems. https://doi.org/10.1103/physrevb.96.165429

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