Strong Spin Filtering by Silicon Nanoparticles with Adsorbed Bismuth Atom Clusters: Role of Symmetry and Electrostatic Control of the Direction of the Spin Polarization

TL;DR

This study uses theoretical modeling to demonstrate that silicon nanoparticles with adsorbed bismuth atom clusters can achieve strong, tunable spin filtering and control of spin polarization direction, promising for spintronic devices.

Contribution

It introduces a novel silicon-bismuth nanostructure with symmetry-based spin filtering and electrostatic control of spin polarization, supported by density functional theory and tight binding calculations.

Findings

Strong spin filtering in high conductance regime

Electrostatic tuning of spin polarization direction

Feasibility of experimental realization

Abstract

We present a theoretical study, based on density functional theory and tight binding modeling, of the electronic structure and spin transport properties of silicon nanoparticles with adsorbed bismuth atoms. We find the bismuth atoms to form clusters separated by quantum tunnel barriers. We predict strong spin filtering by these nanostructures in the high conductance regime when the source and drain leads are connected to the same bismuth cluster and in the low conductance regime when the source and drain leads are connected to different bismuth clusters. We relate the spin filtering to a symmetry obeyed by the spin transmission probability matrix of the system. We also predict that for such systems the direction of the spin polarization in the drain lead can be tuned through large angles and even reversed electrostatically simply by varying the voltage applied to a gate. Realization of these silicon-bismuth nanostructures in the laboratory is feasible. We expect the predicted spin filtering to be experimentally accessible and potentially relevant for device applications.