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

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 de-multiplexer 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.

Real Space Theory for Electron and Phonon Transport in Aperiodic Lattices via Renormalization

“…This interference enables high-performance molecular switching with large on/off ratios essential for the next generation of molecular electronics [110,111], where the RSRM has been used for the study of Fibonacci arrays of Aharonov-Bohm rings [112], metal-insulator transition in the quasiperiodic Aubry model [113], electronic transmission in bent quantum wires [114], and in ladders with a single side-attached impurity [115]. Recently, the electronic density of states, localization, transmittance, and persistent current in molecular chains and ladders have been widely investigated via RSRM [116][117][118][119][120][121][122], while the spin-selective electronic transport was also analyzed [123,124]. A review of these studies is presented in [125].…”

Engineering insulator-metal transition in a class of decorated aperiodic lattices: a quantum dynamical study

“…In some cases, a properly tuned external magnetic flux trapped in the constituent 'cells' of the lattice structures triggered such a complete (or, almost complete) delocalization of the single particle states. The basic scheme was extended to study the spin polarized transport and spin filtering effect in a quasiperiodic arrangement of the 'building blocks' of such geometrically disordered lattices, where an external magnetic flux played a key-role 20 . However, a study of a possible engineering of such complete, or quasi-complete delocalization, through a close scrutiny of the quantum dynamics of the wave packet is still lacking, and this is our primary motivation for the present work.…”

Spin-polarized localization in a magnetized chain

“…We do this through an exhaustive calculation of the spin-resolved localization lengths , specifically designed for our purpose, in various cases of disorder and employing a transfer matrix method (TMM). We use a tight binding model, similar to what we employed before 31,32 . A chain of magnetic atoms is considered and randomness is introduced in the values of the on-site potentials and in the magnitudes as well as in the orientations of the magnetic moments with respect to a preferred axis as shown in Fig.…”

“…The idea was later implemented to study the interplay of quasiperiodic arrangements and the topology of specific model networks comprising magnetic and non-magnetic atoms, having a minimal quasi-one dimensionality. It was shown how a hidden dimension in the linear chain of networks opened up, depending on the spin state of the incoming projectile 32 , which could be exploited to filter out any desired spin channel. The correlations between the parameters of the Hamiltonian and an external magnetic field were found crucial in delocalizing almost all the single particle states over continuous zones in the energy spectrum, thus obtaining a clean spin filtering.…”