# Flux driven and geometry controlled spin filtering for arbitrary spins in aperiodic quantum networks

## TL;DR

This paper presents a method to design aperiodic quantum networks that act as perfect spin filters for particles of any spin, using flux control and geometry tuning, with potential applications in photonic systems.

## Contribution

It introduces a novel approach to achieve arbitrary spin filtering in aperiodic quantum networks through flux and geometry tuning, supported by exact analytical and numerical methods.

## Key findings

- Achieves perfect spin filtering for arbitrary spins.
- Demonstrates flux-controlled spin demultiplexer design.
- Provides exact analytical conditions for spin filtering.

## Abstract

We demonstrate that an aperiodic array of certain quantum networks comprising magnetic and non-magnetic atoms can act as perfect spin filters for particles with arbitrary spin state. This can be achieved by introducing minimal quasi-one dimensionality in the basic structural units building up the array, along with an appropriate tuning of the potential of the non-magnetic atoms, the tunnel hopping integral between the non-magnetic atoms and the backbone, and, in some cases, by tuning an external magnetic field. This latter result opens up the interesting possibility of designing a flux controlled spin demultiplexer using quantum networks. The proposed networks have close resemblance with a family of recently developed photonic lattices, and the scheme for spin filtering can thus be linked, in principle, to a possibility of suppressing any one of the two states of polarization of a single photon, almost at will. We use transfer matrices and a real space renormalization group scheme to unravel the conditions under which any aperiodic arrangement of such topologically different structures will filter out any given spin projection. Our results are analytically exact, and corroborated by extensive numerical calculations of the spin polarized transmission and the density of states of such systems.