Floquet-engineered diode performance of a topological Josephson junction composed of two Kitaev chains coupled via a quantum dot

Abstract

We study nonreciprocal signatures of Josephson current in a quantum dot (QD)-based Josephson junction that comprises two periodically driven Kitaev chains (KCs) coupled with an intervening QD. The simultaneous breaking of the inversion symmetry and the time-reversal symmetry, indispensable for the Josephson diode effect (JDE), is achieved solely via the two Floquet drives that differ by a finite phase, which eventually results in a nonreciprocal current and hence yields a finite JDE. It may be noted that the Floquet Majorana modes generated at both the far ends of the KCs (away from the QD) and adjacent to the QD junctions mediate the Josephson current owing to a finite superconducting (SC) phase difference in the two KCs. We calculate the time-averaged Josephson current and inspect the tunability of the current-phase relation to ascertain the diode characteristics. The asymmetric Floquet drive also manifests an anomalous Josephson current signature in our KC-QD-KC Josephson junction. Furthermore, additional control over the QD energy level can be achieved via an external gate voltage that renders flexibility for the diode to act as an SC switching device. Tuning different system parameters, such as the chemical potential of the KCs, Floquet frequency, the relative phase mismatch of the drives, and the gate voltage, our model shows a maximum rectification ∼70%. Summarizing, in our study, we provide an alternative scenario, replacing the traditional usage of an external magnetic field and spin-orbit coupling effects in a Josephson diode via asymmetrically driven Kitaev leads that entail Majorana-mediated transport.

Source-reported materials — not catalogue approval

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