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DY: Fachverband Dynamik und Statistische Physik

DY 5: Many-body Systems: Equilibration, Chaos and Localization I (joint session DY/TT)

DY 5.9: Vortrag

Montag, 16. März 2020, 12:15–12:30, HÜL 186

Quantum coherent dynamical extension to RKKY interaction — •Stephanie Matern and Bernd Braunecker — School of Physics and Astronomy, University of St Andrews, UK

We study the full time evolution of a pair of impurity spins coupled to a bath of itinerant electrons. Even if the spins do not interact directly they can be coupled through the bath. In its simplest form this corresponds to the RKKY interaction. However, the RKKY interaction is considered as instantaneous and disregards that the spins are not just affected by the response of the bath but have an influence on the bath itself. To capture this effect on the dynamics we take into account all temporal correlations, particularly the quantum coherent correlations building up between the spins and the bath. This immediately leads to non-Markovian dynamics and to a coupling between the spins induced by the coherent quantum excitations of the electron bath. This effective coupling can be considered as a dynamical quantum coherent extension to the RKKY interaction.

Our approach is based on a self-consistent projection operator calculation for generalised quantum master equations. This method allows us to keep track of the time evolution of both the spins and the electron bath, and therefore for the bath to go beyond the usual assumption that it is represented by a Gibbs equilibrium state.