Spin-orbital coupling effect on Josephson current through a superconductor heterojunction

TL;DR

This paper investigates how spin-orbital coupling influences the Josephson current in a superconductor-2DEG-superconductor junction, revealing oscillations and phase transitions driven by SOC strength and type.

Contribution

It introduces a detailed analysis of the impact of Rashba and Dresselhaus SOC on Josephson current, including the discovery of $0$-$ p$ transitions influenced by SOC ratio and layer length.

Findings

Critical current exhibits damped oscillations with SOC strength and layer length.

The SOC ratio can induce switching between $0$ and $ p$ states.

SOC acts like a pseudo-magnetic field affecting electron phase.

Abstract

We study spin-orbital coupling effect on the Josephson current through a superconductor (SC) heterojunction, consisting of two s-wave superconductors and a two-dimensional electron gas (2DEG) layer between them. The Rashba-type (RSOC) and/or Dresselhaus-type (DSOC) of spin-orbital coupling are considered in the 2DEG region. By using the lattice Bogoliubov-de Gennes equation and the Keldysh formalism, we calculate the DC supercurrent flowing through the junction and find that the critical current $I_c$ exhibits a damped oscillation with both the strength of SOC and the layer length of 2DEG; especially, the strength ratio between RSOC and DSOC can also induce switching between the $0$ state and the $\pi$ state of the SC/2DEG/SC junction as well. This $0$-$\pi$ transition results from the fact that SOC in a two-dimension system can lead to a pseudo-magnetic effect on the flowing electrons like the effect of a ferromagnet, since the time reversal symmetry of the system has already been broken by two SC leads with different macroscopic phases.