We investigate dipolar Bose-Einstein condensates in a complex external double-well potential that features a combined parity and time-reversal symmetry. On the basis of the Gross-Pitaevskii equation we study the effects of the long-ranged anisotropic dipole-dipole interaction on ground and excited states by the use of a time-dependent variational approach. We show that the property of a similar non-dipolar condensate to possess real energy eigenvalues in certain parameter ranges is preserved despite the inclusion of this nonlinear interaction. Furthermore, we present states that break the PT symmetry and investigate the stability of the distinct stationary solutions. In our dynamical simulations we reveal a complex stabilization mechanism for PT-symmetric, as well as for PT-broken states which are, in principle, unstable with respect to small perturbations.
Abstract. Dipolar Bose-Einstein condensates in triple-well potentials are well-suited model systems for periodic optical potentials with important contributions of the non-local and anisotropic dipole-dipole interaction, which show a variety of effects such as self-organisation and formation of patterns. We address here a macroscopic sample of dipolar bosons in the mean-field limit. This work is based on the Gross-Pitaevskii description of dipolar condensates in triple-well potentials by Peter et al 2012 J. Phys. B: At. Mol. Opt. Phys. 45 225302. Our analysis goes beyond the calculation of ground states presented there and clarifies the role of excited and metastable states in such systems. In particular, we find the formation of phases originating from the interplay of several states with distinct stability properties. As some of the phases are formed by metastable states special attention is paid to the characteristics of phase transitions in real-time and the dynamical stabilisation of the condensate.
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