Density-wave instability and collective modes in a bilayer system of antiparallel dipoles

Abstract

We consider a bilayer of dipolar particles in which the polarization of dipoles is perpendicular to the planes, in the antiparallel configuration. Using accurate static structure factor ( ) S q data from hypernetted-chain (HNC) and Fermi HNC calculations, respectively for an isolated layer of dipolar bosons and dipolar fermions, we construct effective screened intralayer interactions. Adopting the random-phase approximation for interlayer interactions, we investigate the instability of these homogeneous bilayer systems towards the formation of density waves by studying the poles of the density-density response function. We have also studied the collective modes of these systems and find that the dispersion of their antisymmetric collective mode signals the emergence of the density wave instability as well.

Counterflow in Bose gas bilayers: Collective modes and dissipationless drag

“…Many-body correlations would break the degeneracy of these two modes at strong couplings. 24,25 For softcore short-range interaction, again both density modes are linear at long wavelengths but the velocity of two modes is different.…”

“…where C dd is the dipole-dipole coupling constant, and the direction of polarization in two layers is considered apposite to each other, in order to avoid binding of dipoles from different layers. 25 In practice, such a configuration could be realized with ultra-cold polar molecules subjected to an external static electric field applied to polarize the dipoles. One would then excite molecules in two adjacent layers into two different rotational states, such that their effective polarization become respectively parallel and antiparallel to the applied external electric field.…”

p‐Wave Superfluid Phases of Fermi Molecules in a Bilayer Lattice Array

“…Molecules can move through sites in a given layer, but they cannot tunnel between layers. Given the arrangement illustrated in Figure , several interactions between pairs can arise, such interactions being essential to define the possible phases or ordered structures as stripes or checkerboard patterns . The purpose of this work is to study the p ‐wave superfluidity emerging from attractive interactions between molecules lying in layers A and B .…”

Optimized correlations inspired by perturbation theory

“…For the ground state, this is comparable with stepping from VMC to released node diffusion MC. The CBF route is also the prime tool to extend the theory to excited states [26][27][28][29][30][31]. Again, in terms of accuracy versus computation time, obtaining dynamic properties via FHNC+CBF is much more efficient than by MC [11,30].…”