Nonreciprocal charge transport and subharmonic structure in voltage-biased Josephson diodes

A. Zazunov; J. Rech; T. Jonckheere; B. Grémaud; T. Martin; R. Egger

doi:10.1103/PhysRevB.109.024504

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Nonreciprocal charge transport and subharmonic structure in voltage-biased Josephson diodes

A. Zazunov, J. Rech, T. Jonckheere, B. Grémaud, T. Martin, R. Egger

DOI 10.1103/PhysRevB.109.024504 · Physical Review B

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Abstract

We study charge transport in voltage-biased single-channel junctions involving helical superconductors with finite Cooper pair momentum. For a Josephson junction, the equilibrium current-phase relation shows a superconducting diode effect: the critical current depends on the propagation direction. We formulate a scattering theory for voltage-biased Josephson diodes and show that multiple Andreev reflection processes cause a rich subharmonic structure in the dc current-voltage curve at low temperatures and small voltages due to Doppler shifts of the spectral gap. In the current-biased case, the diode efficiency has maximal rectification efficiency η0≈0.4 for this model. In the voltage-biased case, however, the rectification efficiency can reach the ideal value η=1. We also discuss charge transport for normal-superconducting junctions between a normal metal and a helical superconductor and comment on related models with spin-orbit interactions and magnetic Zeeman fields.