Inertia effects in the real-time dynamics of a quantum spin coupled to a Fermi sea

Abstract

Spin dynamics in the Kondo impurity model, initiated by suddenly switching the direction of a local magnetic field, is studied by means of the time-dependent density-matrix renormalization group. Quantum effects are identified by systematic computations for different spin quantum numbers $S$ and by comparing with tight-binding spin-dynamics theory for the classical-spin Kondo model. We demonstrate that, besides the conventional precessional motion and relaxation, the quantum-spin dynamics shows nutation, similar to a spinning top. Opposed to semiclassical theory, however, the nutation is efficiently damped on an extremely short time scale. The effect is explained in the large-$S$ limit as quantum dephasing of the eigenmodes in an emergent two-spin model that is weakly entangled with the bulk of the system. We argue that, apart from the Kondo effect, the damping of nutational motion is essentially the only characteristics of the quantum nature of the spin. Qualitative agreement between quantum and semiclassical spin dynamics is found down to $S=1/2$.

arXiv comment7+2 pages, 4 figures

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• Anomalous spin precession under a geometrical torque
• An observable effect of spin inertia in slow magneto-dynamics: Increase of the switching error rates in nanoscale ferromagnets
• Topological spin torque emerging in classical-spin systems with different time scales
• Bath-induced spin inertia
• Emergent Non-Abelian Gauge Theory in Coupled Spin-Electron Dynamics
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• Dynamics of spin relaxation in nonequilibrium magnetic nanojunctions
• Nonequilibrium dynamics in a spin valve with noncollinear magnetization
• Non-Hamiltonian dynamics of indirectly coupled classical impurity spins
• Microscopic theory of spin friction and dissipative spin dynamics
• Geometrical torque on magnetic moments coupled to a correlated antiferromagnet
• Relaxation dynamics of a quantum spin coupled to a topological edge state