Andreev reflection resonant tunneling through a precessing spin

TL;DR

This paper studies how a precessing spin influences Andreev reflection tunneling, revealing oscillations in conductance at twice the Larmor frequency and emphasizing the role of spin-orbit interaction and spin-flip tunneling.

Contribution

It provides a theoretical formula for AR conductance considering spin precession, spin-orbit effects, and spin-flip tunneling, highlighting their impact on conductance oscillations.

Findings

AR conductance oscillates at twice the Larmor frequency.

Spin-orbit interaction enhances conductance oscillation amplitude.

Spin-flip tunneling coupling influences resonant tunneling behavior.

Abstract

We investigate Andreev reflection (AR) resonant tunneling through a precessing spin which is coupled to a normal metallic lead and a superconducting lead. The formula of the AR conductance at zero temperature is obtained as a function of chemical potential and azimuthal angle of the spin precessing by using the nonequilibrium Green function method. It is found that as the local spin precesses in a weak external magnetic field at Larmor frequency $\omega_l$, the AR tunneling conductance exhibits an oscillation at the frequency $2\omega_l$ alone. The amplitude of AR conductance oscillation enhances with spin-flip tunneling coupling increasing. The study also shows that spin-orbit interaction in tunneling barriers is crucial for the oscillations of AR conductance. The effect of spin-flip tunneling coupling caused by spin-orbit interaction and local spin precessing on resonant behavior of the AR conductance are examined.