Dresden 2006 – wissenschaftliches Programm

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DY: Dynamik und Statistische Physik

DY 20: Quantum Dynamics I

DY 20.2: Vortrag

Dienstag, 28. März 2006, 10:00–10:15, H\"UL 186

Thermal and Nonthermal Relaxation in Spin Environments — •Harry Schmidt and Günter Mahler — Institut für Theoretische Physik 1, Universität Stuttgart

We investigate a small quantum system (the “central system”, typically a spin-1/2 particle), coupled to a large environment. The environments considered typically also consist of many spin-1/2 particles. Though large, the environment is not treated by a reservoir approximation but is modeled explicitly and the time evolution of the total system is treated exactly.

We are interested in the equilibrium state of the central system after relaxation from a product state. If the environment is initially in a thermal state with a given temperature and the central system relaxes to a thermal state with the same temperature, the relaxation process is called “canonical” or “thermal”. Here we show that not all types of environments exhibit such a canonical relaxation. In particular, we present a method to quantitatively distinguish systems showing canonical relaxation from those that do not. This method is applied to spin environments with and without internal interaction showing a qualitative change in the relaxation behavior due to the interaction.

[1] Schmidt, Mahler: PRE 72, 016117 (2005)