Stability and excitations of a bilayer of strongly correlated dipolar bosons
Abstract
We study correlation effects and excitations in a dipolar Bose gas bilayer which is modeled by a onedimensional doublewell trap that determines the width of an individual layer, the distance between the two layers, and the height of the barrier between them. For the groundstate calculations we use the hypernettedchain EulerLagrange method, and for the calculation of the excitations we use the correlated basis function method. We observe instabilities both for wide, wellseparated layers dominated by intralayer attraction of the dipoles, and for narrow layers that are close to each other dominated by interlayer attraction. The behavior of the pair distribution function leads to the interpretation that the monomer phase becomes unstable when pairing of two dipoles becomes energetically favorable between or within layers, respectively. In both cases we observe a tendency towards “rotonization,” i.e., the appearance of a soft mode with finite momentum in the excitation spectrum. The dynamic structure function is not simply characterized by a single excitation mode but has a nontrivial multipeak structure that is not captured by the BijlFeynman approximation. The dipoledipole interaction between different layers leads to additional damping compared to the damping obtained for uncoupled layers.
 Publication:

Physical Review A
 Pub Date:
 March 2013
 DOI:
 10.1103/PhysRevA.87.033624
 arXiv:
 arXiv:1301.0343
 Bibcode:
 2013PhRvA..87c3624H
 Keywords:

 03.75.Hh;
 03.75.Kk;
 67.85.De;
 Static properties of condensates;
 thermodynamical statistical and structural properties;
 Dynamic properties of condensates;
 collective and hydrodynamic excitations superfluid flow;
 excitations and superfluid flow;
 Condensed Matter  Quantum Gases
 EPrint:
 11 pages