Effect of spin-orbit interaction on the quantum transport in quantum-dot Josephson junctions in the Kondo regime
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- Speaker: Minchul Lee (Kyung Hee University, Korea)
- Event: Quantum Technology Workshop 2026
In this talk we present the study on the effect of the spin-orbit interaction on the phase transitions and superconducting transport of quantum-dot Josephson junctions in the Kondo regime. We adopt the simplest model incorporating the spin-orbit interaction, in which the quantum dot has a single spinful level but an effective direct tunneling between two superconducting leads is opened, giving rise to nontrivial interference between two tunneling paths which can be modulated by the spin-orbit interaction. First, we found that the direct tunneling, if strong enough, can induce singlet-doublet phase transition which is opposite to one found in conventional quantum-dot Josephson junctions, producing a rich phase diagram: for example, there exists a phase where the junction is of spin doublet near $\phi=0$ and of spin singlet near $\phi=\pi$, where $\phi$ is the superconducting phase difference between two leads. Moreover, a finite spin-orbit interaction induces an effective Zeeman field whose magnitude is modulated by the superconducting phase $\phi$ as well and affects the phase transition and current in a nontrivial way, preferring the spin-polarized state. Finally, we propose a way to detect the role of spin-orbit interaction by examining the transport response with respect to the external magnetic field which induces a Zeeman field in the quantum dot.