"Bosonic Gases with Impurities and Dipolar Interactions"
Dorte Blume
Washington State University
Wednesday, February 1, 2006 11 AM -12 Noon in 375 LeConte Hall
Abstract
The behaviors of weakly interacting Bose gases have been
successfully modeled within a mean-field framework. To this end,one
replaces the true atom-atom potential by a contact interaction, and solves the
resulting many-body Schroedinger equation at the Hartree level. The resulting non-linear single-particle
Schroedinger equation, also referred to as Gross-Pitaevskii equation,
predicts many behaviors of inhomogeneous Bose gases accurately, including the onset of instability
for Bose systems with with negative two-body s-wave scattering length for a
critical number of particles. Rapid advances in trapping and cooling now allow ions or
impurities in ultracold gases to be studied and molecular gases to be created. Motivated by
these experimental efforts, the first part of this talk discusses the phase diagram of impurities in
inhomogeneous Bose gases. Employing a simple mean-field framework, a regime where the
impurity is located at the center of the atom cloud is identified. For negative atom-impurity
and positive atom-atom scattering lengths, we find that the system collapses for a critical
set of parameters. This behavior shows similarities to the collapse of inhomogeneous pure Bose gases
with negative atom-atom scattering length. The second part of this talk discusses
the behaviors of dipolar Bose gases. We determine the energetics of a molecular
gas, for which the dipole moment can be varied through application of external fields,
within a mean-field framework and within an essentially exact many-body Monte Carlo framework.
Our results indicate consequences for the collapse of cold Bose gases, consisting of
polar molecules with non-negligible dipole moment.
