237 research outputs found
Weak crystallization theory of metallic alloys
We extend the Weak Crystallization theory to the case of metallic alloys. The
additional ingredient -- itinerant electrons -- generates nontrivial dependence
of free energy on the angles between ordering wave vectors of ionic density.
That leads to stabilization of FCC, Rhombohedral, and icosahedral
quasicrystalline (iQC) phases, which are absent in the generic theory with only
local interactions. The condition for stability of iQC that we find, is
consistent with the Hume-Rothery rules known empirically for majority of stable
iQC; namely, the length of the primary Bragg peak wavevector is approximately
equal to the diameter of the Fermi surface.Comment: 10 pages, 5 figure
Confinement induced interlayer molecules: a route to strong interatomic interactions
We study theoretically the interaction between two species of ultracold atoms
confined into two layers of a finite separation, and demonstrate the existence
of new types of confinement-induced interlayer bound and quasi-bound molecules:
these novel exciton-like interlayer molecules appear for both positive and
negative scattering lengths, and exist even for layer separations many times
larger than the interspecies scattering length. The lifetime of the quasi-bound
molecules grows exponentially with increasing layer separation, and they can
therefore be observed in simple shaking experiments, as we demonstrate through
detailed many-body calculations. These quasi-bound molecules can also give rise
to novel interspecies Feshbach resonances, enabling one to control
geometrically the interaction between the two species by changing the layer
separation. Rather counter-intuitively, the species can be made strongly
interacting, by increasing their spatial separation. The separation induced
interlayer resonances provide a powerful tool for the experimental control of
interspecies interactions and enables one to realize novel quantum phases of
multicomponent quantum gases.Comment: 13 pages, 9 figure
Vortex-Peierls States in Optical Lattices
We show that vortices, induced in cold atom superfluids in optical lattices,
may order in a novel vortex-Peierls ground state. In such a state vortices do
not form a simple lattice but arrange themselves in clusters, within which the
vortices are partially delocalized, tunneling between classically degenerate
configurations. We demonstrate that this exotic quantum many-body state is
selected by an order-from-disorder mechanism for a special combination of the
vortex filling and lattice geometry that has a macroscopic number of
classically degenerate ground states.Comment: 4 pages, 4 figures. Published versio
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Semiclassical Solitons in Strongly Correlated Systems of Ultracold Bosonic Atoms in Optical Lattices
We investigate theoretically soliton excitations and dynamics of their formation in strongly correlated systems of ultracold bosonic atoms in two and three dimensional optical lattices. We derive equations of nonlinear hydrodynamics in the regime of strong interactions and incommensurate fillings, when atoms can be treated as hard core bosons. When parameters change in one direction only we obtain Korteweg–de Vries type equation away from half-filling and modified KdV equation at half-filling. We apply this general analysis to a problem of the decay of the density step. We consider stability of one dimensional solutions to transverse fluctuations. Our results are also relevant for understanding nonequilibrium dynamics of lattice spin models.Physic
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Superfluid-insulator Transition in Fermi-Bose Mixtures and the Orthogonality Catastrophe
The superfluid-insulator transition of bosons is strongly modified by the presence of Fermions. Through an imaginary-time path integral approach, we derive the self-consistent mean-field transition line, and account for both the static and the dynamic screening effects of the fermions. We find that an effect akin to the fermionic orthogonality catastrophe, arising from the fermionic screening fluctuations, suppresses superfluidity. We analyze this effect for various mixture parameters and temperatures, and consider possible signatures of the orthogonality catastrophe effect in other measurables of the mixture.Physic
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