Bulg. J. Phys. vol.42 no.1 (2015), pp. 053-067

Capillary Waves at the Interface of Two Bose–Einstein Condensates. Long Wavelengths Asymptotic by Trial Function Approach

T.M. Mishonov
Department of Theoretical Physics, Faculty of Physics, St. Clement of Ohrid University of Sofia, 5 J. Bourchier Blvd., BG-1164 Sofia, Bulgaria
Abstract. The dispersion relation for capillary waves at the boundary of two different Bose condensates is investigated using a trial wave-function approach applied to the Gross-Pitaevskii (GP) equations. The surface tension is expressed by the parameters of the GP equations. In the long wave-length limit the usual dispersion relation is re-derived while for wavelengths comparable to the healing length we predict significant deviations from the ω ∝ k3/2 law which can be experimentally observed. We approximate the wave variables by a frozen order parameter, i.e. the wave function is frozen in the superfluid analogous to the magnetic field in highly conductive space plasmas.

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