Abstract
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 rather than a periodicity. This effect is a consequence of the conservation of fermion parity—the number of electron —in a superconducting junction and is closely related to the 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 as . Possible experiments on HgCdTe quantum wells will be discussed.
- Received 28 April 2008
DOI:https://doi.org/10.1103/PhysRevB.79.161408
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