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arXiv · 1609.01896

Parity anomaly and spin transmutation in quantum spin Hall Josephson junctions

Yang Peng·Yuval Vinkler-Aviv·Piet W. Brouwer·Leonid I. Glazman·Felix von Oppen
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Abstract

We study the Josephson effect in a quantum spin Hall system coupled to a localized magnetic impurity. As a consequence of the fermion parity anomaly, the spin of the combined system of impurity and spin-Hall edge alternates between half-integer and integer values when the superconducting phase difference across the junction advances by $2π$. This leads to characteristic differences in the splittings of the spin multiplets by exchange coupling and single-ion anisotropy at phase differences, for which time-reserval symmetry is preserved. We discuss the resulting $8π$-periodic (or $\mathbb{Z}_4$) fractional Josephson effect in the context of recent experiments.

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Yang Peng, Yuval Vinkler-Aviv, Piet W. Brouwer, Leonid I. Glazman, Felix von Oppen. 2016-12-03. Parity anomaly and spin transmutation in quantum spin Hall Josephson junctions. https://doi.org/10.1103/physrevlett.117.267001

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