Coherent spin ratchets: A spin-orbit based quantum ratchet mechanism for spin-polarized currents in ballistic conductors

TL;DR

This paper introduces a quantum ratchet mechanism leveraging spin-orbit interaction in 2D conductors, enabling directed spin currents without charge flow, tunable via Fermi energy and Rashba coupling.

Contribution

It demonstrates a novel spin ratchet effect in ballistic conductors using symmetry analysis and numerical verification, advancing spintronics control methods.

Findings

Directed spin current generated without charge current

Spin current direction tunable by Fermi energy and Rashba coupling

Validated effect through numerical simulations in ballistic setups

Abstract

We demonstrate that the combined effect of a spatially periodic potential, lateral confinement and spin-orbit interaction gives rise to a quantum ratchet mechanism for spin-polarized currents in two-dimensional coherent conductors. Upon adiabatic ac-driving, in the absence of a static bias, the system generates a directed spin current while the total charge current is zero. We analyze the underlying mechanism by employing symmetry properties of the scattering matrix and numerically verify the effect for different setups of ballistic conductors. The spin current direction can be changed upon tuning the Fermi energy or the strength of the Rashba spin-orbit coupling.