Department of Physics Papers

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Journal Article

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We study junctions between superconductors mediated by the edge states of a quantum-spin-Hall insulator. We show that such junctions exhibit a fractional Josephson effect, in which the current phase relation has a 4π rather than a 2π periodicity. This effect is a consequence of the conservation of fermion parity—the number of electron mod 2—in a superconducting junction and is closely related to the Z2 topological structure of the quantum-spin-Hall insulator. Inelastic processes, which violate the conservation of fermion parity, lead to telegraph noise in the equilibrium supercurrent. We predict that the low-frequency noise due these processes diverges exponentially with temperature T as T→0. Possible experiments on HgCdTe quantum wells will be discussed.


Suggested Citation:
Fu, L. and C.L. Kane. (2009). "Josephson current and noise at a superconductor/quantum-spin-Hall-insulator/superconductor junction." Physical Review B. 79, 161408(R).

© 2009 The American Physical Society


Date Posted: 06 January 2011

This document has been peer reviewed.