Resonant and Kondo tunneling through molecular magnets

TL;DR

This paper investigates electron transport through molecular magnets, focusing on resonant tunneling and Kondo effects, revealing how magnetic anisotropy influences conductance features in strongly coupled systems.

Contribution

It provides a detailed analysis of resonant and Kondo tunneling regimes in molecular magnets, including the impact of magnetic anisotropy on conductance peaks.

Findings

Fine structure in differential conductance persists beyond thermal energies.

Magnetic anisotropy causes splitting of the Kondo peak at low bias.

Stationary impurity spin states are calculated for strong coupling regimes.

Abstract

Transport through molecular magnets is studied in the regime of strong coupling to the leads. We consider a resonant-tunneling model where the electron spin in a quantum dot or molecule is coupled to an additional local, anisotropic spin via exchange interaction. The two opposite regimes dominated by resonant tunneling and by Kondo transport, respectively, are considered. In the resonant-tunneling regime, the stationary state of the impurity spin is calculated for arbitrarily strong molecule-lead coupling using a master-equation approach, which treats the exchange interaction perturbatively. We find that the characteristic fine structure in the differential conductance persists even if the hybridization energy exceeds thermal energies. Transport in the Kondo regime is studied within a diagrammatic approach. We show that magnetic anisotropy gives rise to a splitting of the Kondo peak at low bias voltages.