3,197 research outputs found
Statics and dynamics of phase segregation in multicomponent fermion gas
We investigate the statics and dynamics of spatial phase segregation process
of a mixture of fermion atoms in a harmonic trap using the density functional
theory. The kinetic energy of the fermion gas is written in terms of the
density and its gradients. Several cases have been studied by neglecting the
gradient terms (the Thomas-Fermi limit) which are then compared with the
Monte-Carlo results using the full gradient corrected kinetic energy. A linear
instability analysis has been performed using the random-phase approximation.
Near the onset of instability, the fastest unstable mode for spinodal
decomposition is found to occur at . However, in the strong coupling
limit, many more modes with decay with comparable time scales.Comment: 14 figure
The Observation of Formation and Annihilation of Solitons and Standing Strain Wave Superstructures in a Two-Dimensional Colloidal Crystal
Confining a colloidal crystal within a long narrow channel produced by two
parallel walls can be used to impose a meso-scale superstructure of a
predominantly mechanical elastic character [Chui et al., EPL 2008, 83, 58004].
When the crystal is compressed in the direction perpendicular to the walls, we
obtain a structural transition when the number of rows of particles parallel to
the walls decreases by one. All the particles of this vanishing row are
distributed throughout the crystal. If the confining walls are structured (say
with a corrugation along the length of the walls), then these extra particles
are distributed neither uniformly nor randomly; rather, defect structures are
created along the boundaries resembling "soliton staircases", inducing a
non-uniform strain pattern within the crystal. Here we study the conditions of
stability, formation and annihilation of these solitons using a coarse grained
description of the dynamics. The processes are shown by comparing superimposed
configurations as well as molecular animations obtained from our simulations.
Also the corresponding normal and shear stresses during the transformation are
calculated. A study of these dynamical processes should be useful for
controlling strain wave superstructures in the self-assembly of various nano-
and meso scaled particles.Comment: 26 pages, 6 figure
Effective interactions and melting of a one dimensional defect lattice within a two-dimensional confined colloidal solid
We report Monte Carlo studies of a two-dimensional soft colloidal crystal
confined in a strip geometry by parallel walls. The wall-particle interaction
has corrugations along the length of the strip. Compressing the crystal by
decreasing the distance between the walls induces a structural transition
characterized by the sudden appearance of a one-dimensional array of extended
defects each of which span several lattice parameters, a "soliton staircase".
We obtain the effective interaction between these defects. A Lindemann
criterion shows that the reduction of dimensionality causes a finite periodic
chain of these defects to readily melt as the temperature is raised. We discuss
possible experimental realizations and speculate on potential applications.Comment: 4 pages 5 embedded figure
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