Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 62: Nonequilibrium Quantum Many-Body Systems II (joint session TT/DY)

TT 62.9: Vortrag

Mittwoch, 14. März 2018, 17:30–17:45, H 3010

Anomalous Spin Precession under a Geometrical Torque — •Christopher Stahl^1,2 and Michael Potthoff¹ — ¹I. Institut für Theoretische Physik, Universität Hamburg — ²Institut für Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg

Precession and relaxation predominantly characterize the real-time dynamics of a spin driven by a magnetic field and coupled to a large Fermi sea of conduction electrons. We demonstrate an anomalous precession with frequency higher than the Larmor frequency or with inverted orientation in the limit where the electronic motion adiabatically follows the spin dynamics. For a classical spin, an analytic expression which identifies the finite spin Berry curvature of the conduction electrons as the origin of the anomalous frequency is derived. Complementary studies for the minimal model of two coupled spins and calculations for the Kondo-impurity model verify that the anomalous precession is also present for a quantum spin and suggest that the derived formula for the frequency of the classical spin can be applied to the quantum case by replacing the classical spin components by the corresponding expectation values.
C. Stahl and M. Potthoff, PRL 119, 227203 (2017)