# Heidelberg 2015 – wissenschaftliches Programm

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# A: Fachverband Atomphysik

## A 31: Ultracold Atoms: Trapping and Cooling I (with Q)

### A 31.3: Vortrag

### Donnerstag, 26. März 2015, 11:45–12:00, P/H2

**Prethermalization of atoms due to photon-mediated long-range interactions** — •Stefan Schütz and Giovanna Morigi — Theoretische Physik, Universität des Saarlandes, D-66123 Saarbrücken, Germany

Atoms can spontaneously form spatially ordered structures in optical resonators when they are transversally driven by lasers. This occurs when the laser intensity exceeds a threshold value and results from the mechanical forces on the atoms associated with superradiant scattering into the cavity mode. We treat the atomic motion semiclassically [1] and show that, while the onset of spatial ordering depends on the intracavity-photon number, the stationary momentum distribution is a Gaussian function whose width is determined by the rate of photon losses. Above threshold, the dynamics is characterized by two time scales: after a violent relaxation, the system slowly reaches the stationary state over time scales exceeding the cavity lifetime by several orders of magnitude. In this transient regime the atomic momenta form non-Gaussian metastable distributions, which emerge from the interplay between the long-range dispersive and dissipative mechanical forces of light [2]. We argue that the dynamics of self-organization of atoms in cavities offers a test bed for studying the statistical mechanics of long-range interacting systems.

[1] S. Schütz, H. Habibian, and G. Morigi, Phys. Rev. A **88**, 033427 (2013)

[2] S. Schütz and G. Morigi, Phys. Rev. Lett. **113**, 203002 (2014)