Physics – Condensed Matter – Quantum Gases
Scientific paper
2009-08-13
Phys. Rev. A 80, 053620 (2009)
Physics
Condensed Matter
Quantum Gases
final, extended version with 2 new figures
Scientific paper
10.1103/PhysRevA.80.053620
Disorder modifies the sound-wave excitation spectrum of Bose-Einstein condensates. We consider the classical hydrodynamic limit, where the disorder correlation length is much longer than the condensate healing length. By perturbation theory, we compute the phonon lifetime and correction to the speed of sound. This correction is found to be negative in all dimensions, with universal asymptotics for smooth correlations. Considering in detail optical speckle potentials, we find a quite rich intermediate structure. This has consequences for the average density of states, particularly in one dimension, where we find a "boson dip" next to a sharp "boson peak" as function of frequency. In one dimension, our prediction is verified in detail by a numerical integration of the Gross-Pitaevskii equation.
Gaul Christopher
Mueller Cord A.
Renner Nina
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