Rashba-induced transverse pure spin currents in a four-terminal quantum dot ring

TL;DR

This paper theoretically demonstrates that applying local Rashba spin-orbit interaction in a four-terminal quantum dot ring induces pure spin currents in transverse terminals, controllable by magnetic flux, bias voltage, and quantum dot levels.

Contribution

It introduces a novel method to generate and control pure spin currents in a quantum dot ring using local Rashba interaction and bias, with tunable polarization directions.

Findings

Pure spin currents appear in transverse terminals under certain conditions.

Polarization directions of spin currents can be inverted by adjusting parameters.

Pure spin currents are achieved without net charge flow in the transverse terminals.

Abstract

By applying a local Rashba spin-orbit interaction on an individual quantum dot of a four-terminal four-quantum-dot ring and introducing a finite bias between the longitudinal terminals, we theoretically investigate the charge and spin currents in the transverse terminals. It is found that when the quantum dot levels are separate from the chemical potentials of the transverse terminals, notable pure spin currents appear in the transverse terminals with the same amplitude and opposite polarization directions. Besides, the polarization directions of such pure spin currents can be inverted by altering structure parameters, i.e., the magnetic flux, the bias voltage, and the values of quantum dot levels with respect to the chemical potentials of the transverse terminals.