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Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 98: Topological insulators (TT, jointly with DS, HL, MA, O)

HL 98.9: Talk

Friday, March 15, 2013, 11:45–12:00, H18

Fermion-parity anomaly of the critical supercurrent in the quantum spin-Hall effect — •Jan Dahlhaus1, Dmitry Pikulin1, Timo Hyart1, Henning Schomerus2, and Carlo Beenakker11Instituut-Lorentz, Universiteit Leiden, Niederlande — 2Department of Physics, Lancaster University, United Kingdom

The helical edge state of a quantum spin-Hall insulator can carry a supercurrent in equilibrium between two superconducting electrodes (separation L, coherence length ξ). We calculate the maximum (critical) current Ic that can flow without dissipation along a single edge, going beyond the short-junction restriction L≪ξ of earlier work, and find a dependence on the fermion parity of the ground state when L becomes larger than ξ. Fermion-parity conservation doubles the critical current in the low-temperature, long-junction limit, while for a short junction Ic is the same with or without parity constraints. This provides a phase-insensitive, dc signature of the 4π-periodic Josephson effect.

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