Transport through single-level systems: Spin dynamics in the nonadiabatic regime

TL;DR

This paper explores the nonadiabatic spin dynamics in a coupled spin-electron system using a meanfield approach, revealing the importance of higher-order transitions at low magnetic fields and the potential for spin switching.

Contribution

It introduces a nonadiabatic, semiclassical framework for analyzing spin dynamics in a coupled system, including short-time effects and energy level broadening, extending beyond rate equation approximations.

Findings

Higher-order transitions are significant at low magnetic fields.

Finite bias regimes can exhibit spin switching behavior.

The model captures short-time dynamics and energy broadening effects.

Abstract

We investigate the Fano-Anderson model coupled to a large ensemble of spins under the influence of an external magnetic field. The interaction between the two spin systems is treated within a meanfield-approach and we assume an anisotropic coupling between these two systems. By using a nonadiabatic approach, we make no further approximations in the theoretical description of our system, apart from the semiclassical treatment. Therewith, we can include the short-time dynamics as well as the broadening of the energy levels arising due to the coupling to the external electronic reservoirs. We study the spin dynamics in the regime of low and high bias. For the infinite bias case, we compare our results to those obtained from a simpler rate equation approach, where higher-order transitions are neglected. We show, that these higher-order terms are important in the range of low magnetic field. Additionally, we analyze extensively the finite bias regime with methods from nonlinear dynamics, and we discuss the possibility of switching of the large spin.