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Q: Fachverband Quantenoptik und Photonik

Q 17: Quantengase: Bosonen Dynamik / Disorder

Q 17.8: Talk

Tuesday, March 3, 2009, 12:15–12:30, VMP 6 HS-A

Speed of Sound in Interacting Disordered Bose-Einstein Condensates — •Nina Renner, Christopher Gaul, and Cord A. Müller — Physikalisches Institut, Universität Bayreuth, Germany

Elementary excitations of interacting Bose-Einstein condensates are sound-wave like at low energies. The dispersion relation of these excitations is changed by an external disorder potential, for which we consider spatially correlated Gaussian and speckle potentials. To begin with we treat the many-particle Hamiltonian in the Gross-Pitaevskii mean-field framework. After performing a saddle-point expansion of the energy functional followed by a Bogoliubov transformation we arrive at the Bogoliubov Hamiltonian [1]. Its self energy in the disorder-averaged effective medium describes the correction to the dispersion relation and notably to the speed of sound. In several limiting cases for 1D propagation we find very simple analytical expressions for these corrections. Our analytical results agree with numerical simulations of the propagation of sound waves.

[1] C. Gaul and C. A. Müller, Europhys. Lett. 83, 10006 (2008)