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Beliaev Damping of Quasiparticles in a Bose-Einstein Condensate
Phys. Rev. Lett. 89, 220401 – Published 6 November, 2002
DOI: https://doi.org/10.1103/PhysRevLett.89.220401
Abstract
We report a measurement of the suppression of collisions of quasiparticles with ground state atoms within a Bose-Einstein condensate at low momentum. These collisions correspond to Beliaev damping of the excitations, in the previously unexplored regime of the continuous quasiparticle energy spectrum. We use a hydrodynamic simulation of the expansion dynamics, with the Beliaev damping cross section, in order to confirm the assumptions of our analysis.
Article Text
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For , there are atoms in front and behind the BEC that should be counted in our integration. We use computerized tomography [22] to find the correct atomic distribution. The systematic error caused by naively integrating the absorption image can be as large as 10%, which is unacceptable for our purposes. At higher , these systematic integration effects are verified to be negligible.
Hydrodynamical simulations (described below) indicate that there are few higher order multiple collisions for the experimental parameters. We also find that nearly all the collision products are indeed located in the counting region after TOF, confirming our momentum and atom number counting procedures.
The LDA average of the suppression of collisions for a nonhomogeneous BEC is nearly indistinguishable from the suppression of a homogeneous condensate with the LDA average healing length as defined in [10].
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