Bipolar spin filter in a quantum dot molecule

TL;DR

This paper demonstrates a tunable quantum dot molecule system that acts as a bipolar spin filter by exploiting singlet-triplet transitions driven by competing interactions, promising robust bidirectional spin polarization.

Contribution

It introduces a novel method for spin filtering using a quantum dot molecule with tunable hybridization and analyzes the underlying singlet-triplet transition mechanism.

Findings

Demonstrates spin filtering via singlet-triplet transition

Shows tunability through interdot hybridization

Proposes a broadly useful bidirectional spin polarizer

Abstract

We show that the tunable hybridization between two lateral quantum dots connected to non-magnetic current leads in a `hanging-dot' configuration that can be used to implement a bipolar spin filter. The competition between Zeeman, exchange interaction, and interdot tunneling (molecular hybridization) yields a singlet-triplet transition of the double dot {\it ground state} that allows spin filtering in Coulomb blockade experiments. Its generic nature should make it broadly useful as a robust bidirectional spin polarizer.