Spin filtering in a Rashba-Dresselhaus-Aharonov-Bohm double-dot interferometer

TL;DR

This paper demonstrates that a double-dot interferometer with spin-orbit interactions and magnetic flux can act as a perfect spin filter, controllable by external fields and effective over a range of electron energies.

Contribution

It introduces a new double-dot interferometer design that achieves spin filtering without requiring high symmetry, simplifying experimental implementation.

Findings

The interferometer can block electrons with specific spin polarization.

Spin filtering is controlled solely by external electric and magnetic fields.

The method works effectively in the linear-response regime.

Abstract

We study the spin-dependent transport of spin-1/2 electrons through an interferometer made of two elongated quantum dots or quantum nanowires, which are subject to both an Aharonov-Bohm flux and (Rashba and Dresselhaus) spin-orbit interactions. Similar to the diamond interferometer proposed in our previous papers [Phys. Rev. B {\bf 84}, 035323 (2011); Phys. Rev. B {\bf 87}, 205438 (2013)], we show that the double-dot interferometer can serve as a perfect spin filter due to a spin interference effect. By appropriately tuning the external electric and magnetic fields which determine the Aharonov-Casher and Aharonov-Bohm phases, and with some relations between the various hopping amplitudes and site energies, the interferometer blocks electrons with a specific spin polarization, independent of their energy. The blocked polarization and the polarization of the outgoing electrons is controlled solely by the external electric and magnetic fields and do not depend on the energy of the electrons. Furthermore, the spin filtering conditions become simpler in the linear-response regime, in which the electrons have a fixed energy. Unlike the diamond interferometer, spin filtering in the double-dot interferometer does not require high symmetry between the hopping amplitudes and site energies of the two branches of the interferometer and thus may be more appealing from an experimental point of view.