Polarized currents in Coulomb blockade and Kondo regimes without magnetic fields

TL;DR

This paper demonstrates that quantum dots connected via spin-polarizing quantum point contacts can exhibit spin-polarized currents in Coulomb blockade and Kondo regimes without external magnetic fields, revealing new control mechanisms for spintronic devices.

Contribution

It introduces a novel system where spin polarization occurs without magnetic fields, using lateral spin-orbit fields in quantum point contacts, and analyzes its transport properties with advanced calculations.

Findings

Spin-polarized conductance in Coulomb blockade and Kondo regimes without magnetic fields

Control of spin polarization via lateral gate voltages

Potential for new spintronic device applications

Abstract

We present studies of the Coulomb blockade and Kondo regimes of transport through a quantum dot connected to current leads through spin-polarizing quantum point contacts (QPCs). This structure, arising from the effect of lateral spin-orbit fields defining the QPCs, results in spin-polarized currents even in the absence of external magnetic fields and greatly affects the correlations in the dot. Using equation-of-motion and numerical renormalization group calculations we obtain the conductance and spin polarization for this system under different parameter regimes. We find that the system exhibits spin-polarized conductance in both the Coulomb blockade and Kondo regimes, all in the absence of applied magnetic fields. We analyze the role that the spin-dependent tunneling amplitudes of the QPC play in determining the charge and net magnetic moment in the dot. These effects, controllable by lateral gate voltages, may provide an alternative approach for exploring Kondo correlations, as well as possible spin devices