Zero-conductance resonances and spin-filtering effects in ring conductors subject to Rashba coupling

TL;DR

This paper analyzes how Rashba spin-orbit coupling and tunnel barriers influence zero conductance resonances in a quantum ring, revealing mechanisms to control electron spin polarization for spin-filtering applications.

Contribution

It provides a detailed analysis of zero conductance resonances in AB rings with Rashba coupling, introducing a tunable spin-filtering mechanism based on barrier strength.

Findings

Tunnel barrier strength affects zero-pole structure of transmission.

Breaking of symmetries lifts conductance zeros.

Electron polarization can be controlled via barrier tuning.

Abstract

We investigate the effect of Rashba spin-orbit coupling and of a tunnel barrier on the zero conduc- tance resonances appearing in a one-dimensional conducting Aharonov-Bohm (AB) ring symmet- rically coupled to two leads. The transmission function of the corresponding one-electron problem is derived within the scattering matrix approach and analyzed in the complex energy plane with focus on the role of the tunnel barrier strength on the zero-pole structure characteristic of trans- mission (anti)resonances. The lifting of the real conductance zeros is related to the breaking of the spin-reversal symmetry and time-reversal symmetry of Aharonov-Casher (AC)and AB rings, as well as to rotational symmetry breaking in presence of a tunnel barrier. We show that the polarization direction of transmitted electrons can be controlled via the tunnel barrier strength and discuss a novel spin-filtering design in one-dimensional rings with tunable spin-orbit interaction.