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Q: Fachverband Quantenoptik und Photonik

Q 25: Poster: Quantum Optics and Photonics I

Q 25.5: Poster

Tuesday, March 12, 2019, 16:30–18:30, S Atrium Informatik

Rotational cooling of molecules in a BEC — •Martin Will, Tobias Lausch, and Michael Fleischhauer — University of Kaiserslautern, 67663 Kaiserslautern, Germany

We discuss the rotational cooling of homonuclear diatomic molecules in a Bose-Einstein-condensate (BEC) . For typical molecules there is no frictionless rotation since the dominant cooling occurs via emission of particle-like phonons. Only for macro-dimers, whose size becomes larger than the condensate healing length, a Landau-like, critical angular momentum exists below which phonon emission is suppressed. We find that the phonon-induced angular momentum relaxation is much faster than the cooling of linear motion of impurities in a BEC. This also leads to a finite lifetime of angulons, quasi-particles of rotating molecules coupled to orbital angular-momentum phonons. The lifetimes are however still smaller than typical angulon binding energies. We analyze the dynamics of rotational cooling for homo-nuclear diatomic molecules based on a quantum Boltzmann equation including single- and two-phonon scattering and discuss the effect of thermal phonons. For typical molecules two-phonon scattering becomes relevant at finite temperature.