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We report on our achievement of a Bose-Einstein condensate (BEC) in a gas of chromium atoms [1]. Due to its large magnetic moment (6μΒ), the dipole-dipole interaction strength in chromium is comparable with the contact interaction due to van der Waals interaction. We prove the anisotropic nature of the dipolar interaction by releasing the condensate from a cigar shaped trap and observe, in time of flight measurements, the change of the aspect-ratio for different in-trap orientations of the atomic dipoles [2]. This is the first observation of a mechanical dipolar effect in a gas. We also report on the recent observation of 14 Feshbach resonances in elastic collisions between polarized ultra-cold 52Cr atoms [3].
We used dipolar relaxation to demonstrate the first demagnetization cooling of a gas as proposed in refs. [4].
We also report on our recent Rydberg excitation of a Rb BEC. We observe strong many-body interactions due to van der Waals repulsion in the 43S state. We present model calculations supporting the many-body nature of the observed lineshape.
References 1. A. Griesmaier, J. Werner, S. Hensler, J. Stuhler, and T. Pfau, Phys. Rev. Lett. 94, 160401 (2005) 2. J. Stuhler, A. Griesmaier, T. Koch, M. Fattori, T. Pfau, S. Giovanazzi, P. Pedri, and L. Santos, Phys. Rev. Lett. 95, 150406 (2005) 3. J. Werner, A. Griesmaier, S. Hensler, J. Stuhler and T. Pfau, Phys. Rev. Lett. 94, 183201 (2005) 4. A. Kastler, J. Phys. 6, 255 (1950), S. Hensler, A. Greiner, J. Stuhler, T. Pfau, Europhys. Lett. 71, 918 (2005) |
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