Switching of a Quantum Dot Spin Valve by Single Molecule Magnets

TL;DR

This paper presents a theoretical study of a quantum dot spin valve controlled by single molecule magnets, revealing a novel mechanism where magnetic reversal causes significant changes in molecular orbitals and electrical resistance.

Contribution

It introduces a new physical principle where spin-dependent molecular orbitals cause large resistance changes upon magnetic reversal in a quantum dot system.

Findings

Magnetic reversal of SMMs induces large resistance changes.

Spin-dependent molecular orbitals are key to the spin valve effect.

The phenomenon explains recent experimental observations in carbon nanotube quantum dots.

Abstract

We explore theoretically the spin transport in nanostructures consisting of a gold quantum dot bridging nonmagnetic electrodes and two Mn12-Ph single molecule magnets (SMMs) that are thiol-bonded to the dot but are not in direct contact with the electrodes. We find that reversal of the magnetic moment of either SMM by the application of a magnetic field leads to a large change in the resistance of the dot, i.e., a strong spin valve effect. We show that this phenomenon arises from a novel physical principle: The spin-dependent molecular orbitals that extend over the dot and both SMMs change drastically when the magnetic moment of either SMM is reversed, resulting in a large change in the conduction via those orbitals. The same physics may also be responsible for the spin valve phenomena discovered recently in carbon nanotube quantum dots with rare earth SMMs by Urdampilleta, Klyatskaya, Cleuziou, Ruben and Wernsdorfer [Nature Mater. 10, 502506 (2011)]