Nonequilibrium Dynamics of Anisotropic Large Spins in the Kondo Regime: Time-Dependent Numerical Renormalization Group Analysis

TL;DR

This paper studies the nonequilibrium behavior of large anisotropic spins in the Kondo regime using time-dependent numerical renormalization group methods, revealing slow relaxation, anisotropy effects, and quantum tunneling phenomena.

Contribution

It introduces a detailed analysis of the dynamics of large anisotropic spins in the Kondo regime, highlighting the effects of anisotropy and spin parity on relaxation and tunneling.

Findings

Logarithmically slow relaxation due to underscreening.

Magnetization saturation caused by uniaxial anisotropy.

Quantum spin tunneling and pseudospin-1/2 Kondo effect induced by transverse anisotropy.

Abstract

We investigate the time-dependent Kondo effect in a single-molecule magnet (SMM) strongly coupled to metallic electrodes. Describing the SMM by a Kondo model with large spin S > 1/2, we analyze the underscreening of the local moment and the effect of anisotropy terms on the relaxation dynamics of the magnetization. Underscreening by single-channel Kondo processes leads to a logarithmically slow relaxation, while finite uniaxial anisotropy causes a saturation of the SMM's magnetization. Additional transverse anisotropy terms induce quantum spin tunneling and a pseudospin-1/2 Kondo effect sensitive to the spin parity.