Flux- and tunnel-parity-controlled Josephson nonreciprocity from singlet-triplet competition in a parallel double quantum dot
Abstract
Nonreciprocal supercurrents in interacting nanostructures can arise when the positive and negative critical currents probe inequivalent portions of a phase-dependent many-body spectrum. We study this mechanism in a parallel double-quantum-dot Josephson junction with strong intradot Coulomb repulsion, where local and non-local Cooper-pair transfer coexist. Using exact diagonalization of a zero-bandwidth Hamiltonian with explicit superconducting orbitals, we show that orbital flux and the gauge-invariant tunnel-sign parity control the interference between local Josephson processes and non-local exchange. For detuned dots, this produces flux-tunable singlet, triplet, and doublet ground-state spectral branches and two rectification regimes. Near the boundaries of the charge sector with singly occupied dots [(1,1) sector], doublet branches compete with singlet or triplet branches, yielding diode efficiencies approaching 40%. Within the triplet-dominated (1,1) sector, nearby singlet crossings asymmetrically reshape the ground-state envelope even when both critical-current extrema lie on the triplet-like branch, producing a broader response of order 10-15%. Finite temperature generally suppresses charge-crossover rectification, however, for intermediate temperatures we find an enhancement of both the normalized efficiency and the absolute critical-current asymmetry in the triplet regime. These results establish phase-dependent many-body branch competition as a gate-, flux-, and tunnel-parity-sensitive source of Josephson nonreciprocity.
Related
- Singlet-doublet transitions and Josephson currents in a superconducting ring with a quantum dot
- Limits of phase-controlled Floquet nonreciprocity in a dual-ring microcavity
- Parallel Simulation of Josephson Junctions With Multiplicative Noise
- Evanescent-mode Casimir-Josephson force and gate-controlled resonances in ballistic graphene Josephson junctions
- Phase-Controlled Majorana Zero Modes in Altermagnetic Topological-Insulator Josephson Junctions
BibTeX
@misc{debnath2026flux,
title = {{Flux- and tunnel-parity-controlled Josephson nonreciprocity from singlet-triplet competition in a parallel double quantum dot}},
author = {Debika Debnath and Fernando Dominguez and Patrik Recher},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.01830},
eprint = {2610.01830},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.01830},
}
RIS
TY - UNPB
TI - Flux- and tunnel-parity-controlled Josephson nonreciprocity from singlet-triplet competition in a parallel double quantum dot
AU - Debika Debnath
AU - Fernando Dominguez
AU - Patrik Recher
PY - 2026
DA - 2026/10/01
PB - arXiv
DO - 10.48550/arxiv.2610.01830
UR - https://arxiv.org/abs/2610.01830
AB - Nonreciprocal supercurrents in interacting nanostructures can arise when the positive and negative critical currents probe inequivalent portions of a phase-dependent many-body spectrum. We study this mechanism in a parallel double-quantum-dot Josephson junction with strong intradot Coulomb repulsion, where local and non-local Cooper-pair transfer coexist. Using exact diagonalization of a zero-bandwidth Hamiltonian with explicit superconducting orbitals, we show that orbital flux and the gauge-invariant tunnel-sign parity control the interference between local Josephson processes and non-local exchange. For detuned dots, this produces flux-tunable singlet, triplet, and doublet ground-state spectral branches and two rectification regimes. Near the boundaries of the charge sector with singly occupied dots [(1,1) sector], doublet branches compete with singlet or triplet branches, yielding diode efficiencies approaching 40%. Within the triplet-dominated (1,1) sector, nearby singlet crossings asymmetrically reshape the ground-state envelope even when both critical-current extrema lie on the triplet-like branch, producing a broader response of order 10-15%. Finite temperature generally suppresses charge-crossover rectification, however, for intermediate temperatures we find an enhancement of both the normalized efficiency and the absolute critical-current asymmetry in the triplet regime. These results establish phase-dependent many-body branch competition as a gate-, flux-, and tunnel-parity-sensitive source of Josephson nonreciprocity.
ER -