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Published October 15, 2016 | Submitted + Published
Journal Article Open

Interaction effects in superconductor/quantum spin Hall devices: Universal transport signatures and fractional Coulomb blockade

Abstract

Interfacing s-wave superconductors and quantum spin Hall edges produces time-reversal-invariant topological superconductivity of a type that cannot arise in strictly one-dimensional systems. With the aim of establishing sharp fingerprints of this phase, we use renormalization-group methods to extract universal transport characteristics of superconductor/quantum spin Hall heterostructures where the native edge states serve as leads. We determine scaling forms for the conductance through a grounded superconductor and show that the results depend sensitively on the interaction strength in the leads, the size of the superconducting region, and the presence or absence of time-reversal-breaking perturbations. We also study transport across a floating superconducting island isolated by magnetic barriers. Here, we predict e-periodic Coulomb-blockade peaks, as recently observed in nanowire devices [S. M. Albrecht et al., Nature (London) 531, 206 (2016)], with the added feature that the island can support fractional charge tunable via the relative orientation of the barrier magnetizations. As an interesting corollary, when the magnetic barriers arise from strong interactions at the edge that spontaneously break time-reversal symmetry, the Coulomb-blockade periodicity changes from e to e/2. These findings suggest several future experiments that probe unique characteristics of topological superconductivity at the quantum spin Hall edge.

Additional Information

© 2016 American Physical Society. Received 7 July 2016; published 7 October 2016. We thank D. Nandi, R. Lutchyn, and A. Yacoby for illuminating discussions. We also gratefully acknowledge support from the National Science Foundation through Grant No. DMR-1341822 (D. A., S.-P. L., and J. A.); the NSERC PGSD program (D.A.); the Caltech Institute for Quantum Information and Matter, an NSF Physics Frontiers Center with support of the Gordon and Betty Moore Foundation through Grant No. GBMF1250; and the Walter Burke Institute for Theoretical Physics at Caltech.

Attached Files

Published - PhysRevB.94.165113.pdf

Submitted - 1606.09255v1.pdf

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