2018/05/31 by Stian Hartman, S. T. H. Hartman, Eirik Erlandsen +1 · 9 citations
Physics and Astronomy · #Bose–Einstein condensate #Cold Atom Physics and Bose-Einstein Condensates #Condensed matter physics #Drag #Drag coefficient #Hamiltonian (control theory) #Mechanics #Physics #Quantum mechanics #Quantum, superfluid, helium dynamics #Strong Light-Matter Interactions #Superfluidity #cond-mat.quant-gas
paper · pdf · doi:10.1103/physrevb.98.024512
published in Physical review. B./Physical review. B 98(2) (American Physical Society) · 18 pages, 9 figures. Published in Physical Review B
openalex publication_date 2018/07/20 · arxiv created 2018/08/16 · arxiv updated 2018/08/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The superfluid drag coefficient of a weakly interacting three-component Bose-Einstein condensate is computed on a square optical lattice deep in the superfluid phase, starting from a Bose-Hubbard model with component-conserving, on-site interactions and nearest-neighbor hopping. At the mean-field level, Rayleigh-Schr"odinger perturbation theory is employed to provide an analytic expression for the drag density. In addition, the Hamiltonian is diagonalized numerically to compute the drag within mean-field theory at both zero and finite temperatures to all orders in intercomponent interactions. Moreover, path integral Monte Carlo simulations, providing results beyond mean-field theory, have been performed to support the mean-field results. In the two-component case the drag increases monotonically with the magnitude of the intercomponent interaction \ensuremathγAB between the two components A and B. The increase is independent of the sign of the intercomponent interaction. This no longer holds when an additional third component C is included. Instead of increasing monotonically, the drag can either be strengthened or weakened depending on the details of the interaction strengths, for weak and moderately strong interactions. The general picture is that the drag coefficient between component A and B is a nonmonotonic function of the intercomponent interaction strength \ensuremathγAC between A and a third component C. For weak \ensuremathγAC compared to the direct interaction \ensuremathγAB between A and B, the drag coefficient between A and B can decrease, contrary to what one naively would expect. When \ensuremathγAC is strong compared to \ensuremathγAB, the drag between A and B increases with increasing \ensuremathγAC, as one would naively expect. We attribute the subtle reduction of \ensuremathρd,AB with increasing \ensuremathγAC, which has no counterpart in the two-component case, to a renormalization of the intercomponent scattering vertex \ensuremathγAB via intermediate excited states of the third condensate C. We briefly comment on how this generalizes to systems with more than three components.