Enhancement of the Josephson Current in a Quantum Dot Connected to Majorana Nanowires

We investigate the behavior of the Josephson current in a system composed of a quantum dot (QD) sandwiched between two nanowires by using the nonequilibrium Green's function technique. We consider that the nanowires are in proximity to s-wave superconducror substrates, and Majorana bound states...

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Bibliographic Details
Published in:Nanomaterials (Basel, Switzerland) Switzerland), 2023-04, Vol.13 (9), p.1482
Main Authors: Chi, Feng, Jia, Qiang-Sheng, Liu, Jia, Gao, Qing-Guo, Yi, Zi-Chuan, Liu, Li-Ming
Format: Article
Language:English
Subjects:
Analysis
Communication
Energy
Green's functions
Hybridization
Identification and classification
Josephson current
Josephson effect
Magnetic fields
Majorana nanowires
Nanoparticles
Nanotechnology
Nanowires
Phase shift
Properties
pure spin current
quantum dot
Quantum dots
Sine waves
spin-polarized coupling
Spintronics
Substrates
Wire
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Summary:We investigate the behavior of the Josephson current in a system composed of a quantum dot (QD) sandwiched between two nanowires by using the nonequilibrium Green's function technique. We consider that the nanowires are in proximity to s-wave superconducror substrates, and Majorana bound states (MBSs) are induced at their ends. It is also assumed that the two nanowires are not aligned in the same orientation, but form a bent angle with respect to each other. It is found that when only one spin state on the QD is coupled to the left nanowire, the Josephson current is the typical sinusoidal function of the phase difference between the two nanowires. If both spin states hybridize to the MBSs with equal coupling strengths, the Josephson current then is not a sinusoidal function of the phase difference. In particular, when the bent angle between the two nanowires is π/2 and the two modes of the MBSs in each nanowire are decoupled from each other, the Josephson current is enhanced by about twenty times in magnitude as compared to the former case. Moreover, the simultaneously enhanced currents of the two spin directions are of the same magnitude but flow in opposite directions and they induce a large pure spin current. Our results also show that this abnormally enhanced Josephson current will be suppressed by a vertical magnetic field applied to the QD.
ISSN:2079-4991
2079-4991
DOI:10.3390/nano13091482