15,640 research outputs found
Ground-state properties of fermionic mixtures with mass imbalance in optical lattices
Ground-state properties of fermionic mixtures confined in a one-dimensional
optical lattice are studied numerically within the spinless Falicov-Kimball
model with a harmonic trap. A number of remarkable results are found. (i) At
low particle filling the system exhibits the phase separation with heavy atoms
in the center of the trap and light atoms in the surrounding regions. (ii)
Mott-insulating phases always coexist with metallic phases. (iii)
Atomic-density waves are observed in the insulating regions for all particle
fillings near half-filled lattice case. (iv) The variance of the local density
exhibits the universal behavior (independent of the particle filling, the
Coulomb interaction and the strength of a confining potential) over the whole
region of the local density values.Comment: 10 pages, 5 figure
Phases of lattice hard core bosons in a periodic superlattice
We study by Quantum Monte Carlo simulations the phase diagram of lattice hard
core bosons with nearest-neighbour repulsive interactions, in the presence of a
super-lattice of adsorption sites. For a moderate adsorption strength, the
system forms crystal phases registered with the adsorption lattice; a
"supersolid" phase exists, on both the vacancy and interstitial sides, whereas
at commensuration the superfluid density vanishes. The possible relevance of
these results to experiments on He films adsorbed on graphite is discussed.Comment: 5 pages, 5 figure
Tribological Behavior of Very Thin Confined Films
The tribological properties of two smooth surfaces in the presence of a thin
confined film are investigated with a generic model for the interaction between
two surfaces and with computer simulations. It is shown that at large normal
contact pressures, an ultra thin film automatically leads to static friction
between two flat surfaces - even if the surfaces are incommensurate.
Commensurability is nevertheless the key quantity to understand the
tribological behavior of the contact. Qualitative differences between
commensurate and incommensurate contacts remain even in the presence of a thin
film. The differences mainly concern the thermal diffusion of the contact and
the transition between smooth sliding and stick-slip.Comment: 7 pages, 6 figure
Pfaffian-like ground state for 3-body-hard-core bosons in 1D lattices
We propose a Pfaffian-like Ansatz for the ground state of bosons subject to
3-body infinite repulsive interactions in a 1D lattice. Our Ansatz consists of
the symmetrization over all possible ways of distributing the particles in two
identical Tonks-Girardeau gases. We support the quality of our Ansatz with
numerical calculations and propose an experimental scheme based on mixtures of
bosonic atoms and molecules in 1D optical lattices in which this Pfaffian-like
state could be realized. Our findings may open the way for the creation of
non-abelian anyons in 1D systems
Characteristics of Bose-Einstein condensation in an optical lattice
We discuss several possible experimental signatures of the Bose-Einstein
condensation (BEC) transition for an ultracold Bose gas in an inhomogeneous
optical lattice. Based on the commonly used time-of-flight imaging technique,
we show that the momentum-space density profile in the first Brillouin zone,
supplemented by the visibility of interference patterns, provides valuable
information about the system. In particular, by crossing the BEC transition
temperature, the appearance of a clear bimodal structure sets a qualitative and
universal signature of this phase transition. Furthermore, the momentum
distribution can also be applied to extract the condensate fraction, which may
serve as a promising thermometer in such a system.Comment: 12 pages, 13 figures; Revised version with new figures; Phys. Rev. A
77, 043626 (2008
Mott Transitions of Three-Component Fermionic Atoms with Repulsive Interaction in Optical Lattices
We investigate the Mott transitions of three-component (colors) repulsive
fermionic atoms in optical lattices using the dynamical mean field theory. We
find that for SU(3) symmetry breaking interactions the Mott transition occurs
at incommensurate half filling. As a result, a characteristic Mott insulating
state appears, where paired atoms with two different colors and atoms with the
third color are localized at different sites. We also find another Mott state
where atoms with two different colors are localized at different sites and
atoms with the third color remain itinerant. We demonstrate that these exotic
Mott phases can be detected by experimental double occupancy observations.Comment: 5 pages, 4 figure
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