Wave kinetic description of Bose Einstein condensates

José Tito Mendonça, A. Serbêto, Padma Kant Shukla

Herbert E. Spohn

José Tito Mendonça

Abstract We derive a system of two coupled wave-kinetic equations for the condensate and for the thermal gas. This provides a simple and elegant model, based on a two fluid interaction, in the spirit of the traditional theory of superfluidity. One of the fluids is the condensed gas, and the other is the fluid of bogolon quasi-particles. As an illustration, we apply this wave-kinetic model to the description of the second-sound.

Wu‐Ming Liu

José Tito Mendonça, Hugo Terças, A. Gammal

We consider Landau damping of elementary excitations in Bose-Einstein condensates (BECs) with dipolar interactions. We discuss quantum and quasiclassical regimes of Landau damping. We use a generalized wave-kinetic description of BECs which, apart from the long-range dipolar interactions, also takes into account the quantum fluctuations and the finite-energy corrections to short-range interactions. Such a description is therefore more general than the usual mean-field approximation. The present wave-kinetic approach is well suited for the study of kinetic effects in BECs, such as those associated with Landau damping, atom trapping, and turbulent diffusion. The inclusion of quantum fluctuations and energy corrections changes the dispersion relation and the damping rates, leading to possible experimental signatures of these effects. Quantum Landau damping is described with generality, and particular examples of dipolar condensates in two and three dimensions are studied. The occurrence of roton-maxon excitations, and their relevance to Landau damping, are also considered in detail. The present approach is mainly based on a linear perturbative procedure, but the nonlinear regime of Landau damping, which includes atom trapping and atom diffusion, is also briefly discussed.

Benjamin Schlein