6 research outputs found
Bound Chains of Tilted Dipoles in Layered Systems
Ultracold polar molecules in multilayered systems have been experimentally
realized very recently. While experiments study these systems almost
exclusively through their chemical reactivity, the outlook for creating and
manipulating exotic few- and many-body physics in dipolar systems is
fascinating. Here we concentrate on few-body states in a multilayered setup. We
exploit the geometry of the interlayer potential to calculate the two- and
three-body chains with one molecule in each layer. The focus is on dipoles that
are aligned at some angle with respect to the layer planes by means of an
external eletric field. The binding energy and the spatial structure of the
bound states are studied in several different ways using analytical approaches.
The results are compared to stochastic variational calculations and very good
agreement is found. We conclude that approximations based on harmonic
oscillator potentials are accurate even for tilted dipoles when the geometry of
the potential landscape is taken into account.Comment: 10 pages, 6 figures. Submitted to Few-body Systems special issue on
Critical Stability, revised versio
Dimers, Effective Interactions, and Pauli Blocking Effects in a Bilayer of Cold Fermionic Polar Molecules
We consider a bilayer setup with two parallel planes of cold fermionic polar
molecules when the dipole moments are oriented perpendicular to the planes. The
binding energy of two-body states with one polar molecule in each layer is
determined and compared to various analytic approximation schemes in both
coordinate- and momentum-space. The effective interaction of two bound dimers
is obtained by integrating out the internal dimer bound state wave function and
its robustness under analytical approximations is studied. Furthermore, we
consider the effect of the background of other fermions on the dimer state
through Pauli blocking, and discuss implications for the zero-temperature
many-body phase diagram of this experimentally realizable system.Comment: 18 pages, 10 figures, accepted versio
Layers of Cold Dipolar Molecules in the Harmonic Approximation
We consider the N-body problem in a layered geometry containing cold polar
molecules with dipole moments that are polarized perpendicular to the layers. A
harmonic approximation is used to simplify the hamiltonian and bound state
properties of the two-body inter-layer dipolar potential are used to adjust
this effective interaction. To model the intra-layer repulsion of the polar
molecules, we introduce a repulsive inter-molecule potential that can be
parametrically varied. Single chains containing one molecule in each layer, as
well as multi-chain structures in many layers are discussed and their energies
and radii determined. We extract the normal modes of the various systems as
measures of their volatility and eventually of instability, and compare our
findings to the excitations in crystals. We find modes that can be classified
as either chains vibrating in phase or as layers vibrating against each other.
The former correspond to acoustic and the latter to optical phonons.
Instabilities can occur for large intra-layer repulsion and produce diverging
amplitudes of molecules in the outer layers. Lastly, we consider experimentally
relevant regimes to observe the structures.Comment: 17 pages, 20 figures, accepted versio