Regensburg 2010 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 8: Quantum Dynamics, Decoherence, and Quantum Information I

DY 8.8: Vortrag

Dienstag, 23. März 2010, 11:45–12:00, H38

Open quantum systems: The Third Law and the conundrum of negative specific heat — •Peter Hänggi — Universität Augsburg, Institut für Physik, Universitätsstr. 1, 86135 Augsburg

We consider the validity of the Third Law in open quantum systems and evaluate the specific heat C. Two routes for obtaining C are presented. The first one uses the measurement of the expectation of the system Hamiltonian while the second one is based on the reduced partition function of the open quantum system, which is the ratio of the partition functions of system plus bath and of the bath alone. Both descriptions yield results which are consistent with the Third Law of thermodynamics. Interestingly, the two methods produce different results that disagree even in their leading quantum corrections at high temperatures. As specific examples we use (i) a damped two-level fluctuator, (ii) a damped harmonic oscillator and (iii), a free particle coupled with finite friction strength to a bath. For zero coupling this latter system presents an exception to the validity of the Third Law (ideal gas of free particles). We detect parameter regimes for which the specific heat C of the open system is negative. This issue is contrasted with thermodynamic rigorous stability criteria and resolved. References:

[1-3] G. Ingold, P. Hänggi, and P. Talkner: Specific heat anomalies of open quantum systems, Phys. Rev. E 79, 061105 (2009); P. Hänggi, G. L. Ingold, and P. Talkner: Finite quantum dissipation: the challenge of obtaining specific heat, New J. Phys. 10, 115008 (2008); P. Hänggi and G. L. Ingold: Quantum Brownian motion and the third law of thermodynamics Acta Physica Polonica B 37, 1537 (2006).