Quantum dot-based device for high-performance magnetic microscopy and spin filtering in the Kondo regime

TL;DR

This paper proposes a double quantum dot device that leverages the Kondo effect and magnetic field sensitivity to enable high-performance magnetic microscopy and spin filtering, especially useful for imaging antiferromagnetic surfaces.

Contribution

The study introduces a novel quantum dot device design that exploits magnetic field-dependent transport properties for sensitive magnetic field detection and spin filtering.

Findings

Device exhibits magnetic field-dependent conductance changes.

Partial survival of the Kondo effect under magnetic fields.

Reversal of conductance amplitudes between spin states.

Abstract

We propose a nanoscale device consisting of a double quantum dot with a full exchange and pair hopping interaction. In this design, the current can only flow through the upper dot, but is sensitive to the spin state of the lower dot. The system is immersed in a highly inhomogeneous magnetic field, and only the bottom dot feels a substantial magnetic field, while the top dot experiences only a residual one. We show that our device exhibits very interesting magnetic field-dependent transport properties at low temperatures. The Kondo effect partially survives the presence of the magnetic field and allows to obtain conductances that differ by several orders of magnitude for the two spin types across the top dot. Interestingly, as a function of the magnetic field, our two-dot device changes from a spin singlet state to a spin triplet state, in which the amplitudes of the spin-dependent conductances are reversed. Our device is able to discriminate between positive and negative magnetic fields with a high sensitivity and is therefore particularly interesting for imaging the surface of anti-ferromagnetic (AF) insulating materials with alternated surface magnetic field, as well as for spin filtering applications.