Spin filtering due to quantum interference in periodic mesoscopic networks

TL;DR

This paper extends a spin filter model based on quantum interference in mesoscopic diamond networks, demonstrating tunable spin polarization via electric and magnetic fields, and exploring geometric and energetic effects on filtering efficiency.

Contribution

It introduces a generalized model with rhombus geometries and analyzes how angles and gate voltages affect spin filtering and electron localization.

Findings

Increasing rhombus angles widens filtering parameter range.

Differential gate voltages can delocalize electrons on one side of the band.

Model comparison shows agreement under specific site energy conditions.

Abstract

We present several new results, extending our recent proposal of a spin filter based on a tight-binding model for a periodic chain of diamond-like loops [Phys. Rev. B {\bf 78}, 125328 (2008)]. In this filter, the Rashba spin-orbit interaction (which can be tuned by a perpendicular gate voltage) and the Aharonov-Bohm flux (due to a perpendicular magnetic field) combine to select only one propagating ballistic mode. For this mode, the electronic spins are fully polarized along a direction that can be controlled by the electric and magnetic fields and by the electron energy. All the other modes are evanescent. Generalizing the square diamonds into rhombi with arbitrary opening angles, we find that increasing these angles widens the parameter range for efficient filtering. A different gate voltage on the two sides of each rhombus is found to delocalize the electrons for energies on one side of the band center. We also compare our tight-binding model with models which use continuous quantum networks of one-dimensional wires, and find coincidence only when one chooses particular site energies at the nodes of the network.