Photon-assisted electronic and spin transport in a junction containing precessing molecular spin

TL;DR

This paper investigates how a precessing molecular spin influences ac charge and spin transport in a molecular junction, revealing internal spin dynamics and enabling dc-spin current generation through time-dependent voltages.

Contribution

It introduces a theoretical framework using nonequilibrium Green's functions to analyze spin and charge transport in a molecular junction with precessing spins under ac voltages, highlighting new control mechanisms.

Findings

Detection of Larmor frequency via dc conductance measurements

Generation of dc-spin currents controlled by molecular magnetization

Rich transport structures due to inelastic transitions driven by spin precession

Abstract

We study the ac charge and -spin transport through an orbital of a magnetic molecule with spin precessing in a constant magnetic field. We assume that the source and drain contacts have time-dependent chemical potentials. We employ the Keldysh nonequilibrium Green's functions method to calculate the spin and charge currents to linear order in the time-dependent potentials. The molecular and electronic spins are coupled via exchange interaction. The time-dependent molecular spin drives inelastic transitions between the molecular quasienergy levels, resulting in a rich structure in the transport characteristics. The time-dependent voltages allow us to reveal the internal precession time scale (the Larmor frequency) by a dc conductance measurement if the ac frequency matches the Larmor frequency. In the low-ac-frequency limit the junction resembles a classical electric circuit. Furthermore, we show that the setup can be used to generate dc-spin currents, which are controlled by the molecular magnetization direction and the relative phases between the Larmor precession and the ac voltage.