Electron transport across electrically switchable magnetic molecules

TL;DR

This paper studies electron transport in a magnetic molecule with switchable exchange coupling, revealing negative differential conductance, a critical voltage where current is temperature-independent, and noise characteristics.

Contribution

It introduces a model showing how electric fields can control magnetic exchange coupling and explores resulting transport phenomena, including noise behavior and temperature effects.

Findings

Negative differential conductance at low temperatures

Existence of a critical voltage V_C with temperature-independent current

Quadratic current fluctuations relate to conductance fluctuations and temperature

Abstract

We investigate the electron transport properties of a model magnetic molecule formed by two magnetic centers whose exchange coupling can be altered with a longitudinal electric field. In general we find a negative differential conductance at low temperatures originating from the different scattering amplitudes of the singlet and triplet states. More interestingly, when the molecule is strongly coupled to the leads and the potential drop at the magnetic centers is only weakly dependent on the magnetic configuration, we find that there is a critical voltage V_C at which the current becomes independent of the temperature. This corresponds to a peak in the low temperature current noise. In such limit we demonstrate that the quadratic current fluctuations are proportional to the product between the conductance fluctuations and the temperature.