Dynamics and thermalization of an elementary quantum system in an environment out of thermal equilibrium

Orateur : Dr. Bruno BELLOMO (Université Montpellier 2)

I will discuss the evolution and the thermalization of an elementary quantum atomic system embedded in a sta tionary radiation out of thermal equilibrium [1, 2]. The quantum system is placed close to a body of arbitrary geometry and dielectric permittivity. The body temperature, TM, is kept constant and it is different from that of the surrounding walls, TW. Transition rates and steady states become both qualitatively and quantitatively different from the case at thermal equilibrium. For example, the steady state becomes dependent on the system-­‐body distance, on the atomic frequencies, on the geometry of the body, on the temperatures TM and TW and on the interplay of all such parameters with the body optical resonances. I will show that in the case of a three-­‐level atomic system [1], the steady state is not a thermal state in general and that steady populations can exceed their values at equilibrium. I will discuss how one can exploit this peculiar behavior emerging out equilibrium, to provide inversion of population ordering and an efficient cooling mechanism for the internal temperature of the atomic system. Finally, I will present numerical studies and asymptotic expressions for the case where the body is a slab of finite thickness. These predictions point out new tools to manipulate the dynamics of an atomic system, emerging out equilibrium. These can be relevant for a wide class of experimental configurations in absence of thermal equilibrium, involving real or artificial atoms. [1] B. Bellomo, R. Messina and M. Antezza, Europhys. Lett. (2012), arXiv:1205.6784. [2] B. Bellomo, R. Messina, D. Felbacq and M. Antezza, arXiv:1205.6089. [2] B. Bellomo, R. Messina, D. Felbacq and M. Antezza, arXiv:1205.6089.

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