Dipole-Dipole Interactions in Ultra-Cold Gases
An important feature of the alkali atoms typically used for weakly interacting Bose-Einstein condensates is that their interactions are short-ranged and can be well-approximated by a contact interaction. In 2005 the Stuttgart group obtained the first BEC of chromium, a system with an important new feature: Ground state chromium atoms have a large magnetic dipole moment leading to an appreciable dipole-dipole interaction. These interactions are long-ranged and anisotropic, and a range of new physics is expected to arise. Recently, there were a number of breakthroughs with the condensation of dipolar erbium and dysprosium atoms. There has also been considerable progress towards the production of quantum degenerate polar molecules with large electric dipoles.
In this talk I will review some of the interesting experimental and theoretical work on dipolar systems. Of particular interest is that, in the pancake trap, a momentum dependence of the interaction is predicted which may even lead to a new kind of (weakly interacting) roton. This roton has not been observed experimentally and I will discuss our work that predicts its dramatic manifestation in the density fluctuations. These effects should be observable in current experiments with recent advances in imaging (e.g. the quantum gas microscope).
Host: Ryan Wilson