Directional dependence of spin currents induced by Aharonov-Casher phase

TL;DR

This paper investigates how the Aharonov-Casher phase influences persistent spin currents in an open ring, revealing directional dependence and modulation by spin precession angles, with distinctions between adiabatic and nonadiabatic regimes.

Contribution

It introduces a detailed analysis of the directional dependence of persistent spin currents induced by the Aharonov-Casher phase, including effects of nonadiabatic phases and their relation to the Aharonov-Anandan phase.

Findings

Persistent spin currents exist without charge currents in the ring.

The magnitude of spin current depends on the direction of electron flow.

Periodic behavior of spin current emerges in the adiabatic limit.

Abstract

We have calculated the persistent spin current of an open ring induced by the Aharonov-Casher phase. For unpolarized electrons there exist no persistent charge currents, but persistent spin currents. We show that, in general, the magnitude of the persistent spin current in a ring depends on the direction of the direct current flow from one reservoir to another. The persistent spin current is modulated by the cosine function of the spin precession angle. The nonadiabatic Aharonov-Casher phase gives anomalous behaviors. The Aharonov-Anandan phase is determined by the solid angle of spin precession. When the nonadiabatic Aharonov-Anandan phase approaches a constant value with the increase of the electric field, the periodic behavior of the spin persistent current occurs in an adiabatic limit. In this limit the periodic behavior of the persistent spin current could be understood by the effective spin-dependent Aharonov-Bohm flux.