Field of Expertise: Advanced Material Science

Formation of the Kondo screening cloud
Martin Nuss
15:00 - 17:00 Thursday 23 October 2014 Rechbauerstrasse 12, HSII

We study the nonequilibrium formation of a spin screening-cloud that accompanies the quenching of a local magnetic moment immersed in a Fermi sea at zero temperature. Based on high precision density matrix renormalization group results for the interacting single impurity Anderson model we discuss the real time evolution after a quantum quench in the impurity-reservoir hybridization using time evolving block decimation. We report emergent length and time scales in the spatio-temporal structure of non-local correlation functions in the spin- and the charge density channel. For the equilibrium case our data for the correlation functions and the extracted length-scales show good agreement with existing results. In the time-dependent data, we identify a major signal which defines a "light cone" moving with the Fermi velocity and a ferromagnetic component in its wake. Inside the "light cone" we find that the structure of the nonequilibrium correlation functions emerges on two time scales. Initially, the qualitative structure of the correlation functions builds up fast with the lattice Fermi velocity. Subsequently the spin correlations converge to the equilibrium results on a much larger time scale. This process sets a dynamic energy scale, which we identify to be proportional to the Kondo temperature. Outside the "light cone" we observe two different power law decays of the correlation functions in space, with time and interaction-strength independent exponents.