264 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
Electronic polarons in an extended Falicov-Kimball model
We examine the one-dimensional spinless Falicov-Kimball model extended by a
hybridization potential between the localized and itinerant electron states.
Below half-filling we find a crossover from a mixed-valence metal to an
integer-valence phase separated state with increasing on-site Coulomb
repulsion. This crossover regime is characterized by local competition between
the strong- and weak-coupling behaviour, manifested by the formation of an
electronic polaron liquid. We identify this intermediate-coupling regime as a
charge-analogy of the Griffiths phase; a phase diagram is presented and
discussed in detail.Comment: RevTex, 10 pages, 1 figure; revised discussio
Ground-state properties of the Falicov-Kimball model with correlated hopping in two dimensions
A new numerical method, recently developed to study ground states of the
Falicov-Kimball model (FKM), is used to examine the effects of correlated
hopping on the ground-state properties of this model in two dimensions. It is
shown that the ground-state phase diagram as well as the picture of
metal-insulator transitions found for the conventional FKM (without correlated
hopping) are strongly changed when the correlated hopping term is added. The
effect of correlated hopping is so strong that it can induce the
insulator-metal transition, even in the strong-coupling limit, where the ground
states of the conventional FKM are insulating for all -electron densities.Comment: 11 pages, 2 figures, LaTe
A complete devil's staircase in the Falicov-Kimball model
We consider the neutral, one-dimensional Falicov-Kimball model at zero
temperature in the limit of a large electron--ion attractive potential, U. By
calculating the general n-ion interaction terms to leading order in 1/U we
argue that the ground-state of the model exhibits the behavior of a complete
devil's staircase.Comment: 6 pages, RevTeX, 3 Postscript figure
Entanglement and quantum phase transition in the asymmetric Hubbard chain: density-matrix renormalization group calculations
We study the ground state quantum phase transition by means of entanglement
in the one-dimensional asymmetric Hubbard model with open boundary condition.
The local entanglement between the middle two sites and the rest of the system,
and the block entanglement between the left and right portions of the system,
are calculated using the density-matrix renormalization group (DMRG) method. We
find that the entanglement shows interesting scaling and singular behavior
around the phase transition line.Comment: 9 pages, 17 figures. One figure is remove
Dynamic Impedance of Two-Dimensional Superconducting Films Near the Superconducting Transition
The sheet impedances, Z(w,T), of several superconducting a-Mo77Ge23 films and
one In/InOx film have been measured in zero field using a two-coil mutual
inductance technique at frequencies from 100 Hz to 100 kHz. Z(w,T) is found to
have three contributions: the inductive superfluid, renormalized by nonvortex
phase fluctuations; conventional vortex-antivortex pairs, whose contribution
turns on very rapidly just below the usual Kosterlitz-Thouless-Berezinskii
unbinding temperature; and an anomalous contribution. The latter is
predominantly resistive, persists well below the KTB temperature, and is weakly
dependent on frequency down to remarkably low frequencies, at least 100 Hz. It
increases with T as e-U'(T)/kT, where the activation energy, U'(T), is about
half the energy to create a vortex-antivortex pair, indicating that the
frequency dependence is that of individual excitations, rather than critical
behavior.Comment: 10 pages, 10 figs; subm PR
Phase transitions in the spinless Falicov-Kimball model with correlated hopping
The canonical Monte-Carlo is used to study the phase transitions from the
low-temperature ordered phase to the high-temperature disordered phase in the
two-dimensional Falicov-Kimball model with correlated hopping. As the
low-temperature ordered phase we consider the chessboard phase, the axial
striped phase and the segregated phase. It is shown that all three phases
persist also at finite temperatures (up to the critical temperature )
and that the phase transition at the critical point is of the first order for
the chessboard and axial striped phase and of the second order for the
segregated phase. In addition, it is found that the critical temperature is
reduced with the increasing amplitude of correlated hopping in the
chessboard phase and it is strongly enhanced by in the axial striped and
segregated phase.Comment: 17 pages, 6 figure
Phase separation and the segregation principle in the infinite-U spinless Falicov-Kimball model
The simplest statistical-mechanical model of crystalline formation (or alloy
formation) that includes electronic degrees of freedom is solved exactly in the
limit of large spatial dimensions and infinite interaction strength. The
solutions contain both second-order phase transitions and first-order phase
transitions (that involve phase-separation or segregation) which are likely to
illustrate the basic physics behind the static charge-stripe ordering in
cuprate systems. In addition, we find the spinodal-decomposition temperature
satisfies an approximate scaling law.Comment: 19 pages and 10 figure
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