128 research outputs found
A dynamical mean-field theory study of stripe order and d-wave superconductivity in the two-dimensional Hubbard model
We use cellular dynamical mean-field theory with extended unit cells to study
the ground state of the two-dimensional repulsive Hubbard model at finite
doping. We calculate the energy of states with d-wave superconductivity
coexisting with spatially uniform magnetic order and find that they are
energetically favoured in a large doping region as compared to the uniform
solution. We study the spatial form of the superconducting and magnetic order
parameters at different doping values.Comment: 11 pages, 6 figure
Localization and diffusion in Ising-type quantum networks
We investigate the effect of phase randomness in Ising-type quantum networks.
These networks model a large class of physical systems. They describe micro-
and nanostructures or arrays of optical elements such as beam splitters
(interferometers) or parameteric amplifiers. Most of these stuctures are
promising candidates for quantum information processing networks. We
demonstrate that such systems exhibit two very distinct types of behaviour. For
certain network configurations (parameters), they show quantum localization
similar to Anderson localization whereas classical stochastic behaviour is
observed in other cases. We relate these findings to the standard theory of
quantum localization.Comment: 12 page
Infra-ordinario. Una descripciĂłn del espacio pĂşblico en el tiempo
Infra-ordinario es un estudio urbano de la plazuela de la Campana, un espacio pĂşblico en el centro histĂłrico de Veracruz, MĂ©xico. El tĂ©rmino "infra-ordinario" se refiere a acontecimientos diarios, acciones y hábitos que son anodinos y pasan casi inadvertidos, como caminar, descansar y recrearse en la plazuela. Este estudio muestra la manera en que la vida urbana de este espacio pĂşblico emerge por medio de eventos ordinarios y cĂłmo la morfologĂa urbana y la historia conforman el espacio social
Topological phase transitions in the repulsively interacting Haldane-Hubbard model
Using dynamical mean-field theory and exact diagonalization we study the
phase diagram of the repulsive Haldane-Hubbard model, varying the interaction
strength and the sublattice potential difference. In addition to the quantum
Hall phase with Chern number and the band insulator with present
already in the noninteracting model, the system also exhibits a Mott
insulating phase, and a quantum Hall phase. We explain the latter phase
by a spontaneous symmetry breaking where one of the spin-components is in the
Hall state and the other in the band insulating state.Comment: Updated version, 6 pages, 4 figure
Finite temperature phase diagram of a polarized Fermi gas in an optical lattice
We present phase diagrams for a polarized Fermi gas in an optical lattice as
a function of temperature, polarization, and lattice filling factor. We
consider the Fulde-Ferrel-Larkin-Ovchinnikov (FFLO), Sarma or breached pair
(BP), and BCS phases, and the normal state and phase separation. We show that
the FFLO phase appears in a considerable portion of the phase diagram. The
diagrams have two critical points of different nature. We show how various
phases leave clear signatures to momentum distributions of the atoms which can
be observed after time of flight expansion.Comment: Journal versio
Exotic superfluid states of lattice fermions in elongated traps
We present real-space dynamical mean-field theory calculations for
attractively interacting fermions in three-dimensional lattices with elongated
traps. The critical polarization is found to be 0.8, regardless of the trap
elongation. Below the critical polarization, we find unconventional superfluid
structures where the polarized superfluid and
Fulde-Ferrell-Larkin-Ovchinnikov-type states emerge across the entire core
region
Countable Sofic Shifts with a Periodic Direction
As a variant of the equal entropy cover problem, we ask whether all multidimensional sofic shifts with countably many configurations have SFT covers with countably many configurations. We answer this question in the negative by presenting explicit counterexamples. We formulate necessary conditions for a vertically periodic shift space to have a countable SFT cover, and prove that they are sufficient in a natural (but quite restricted) subclass of shift spaces
Noise correlations of the ultra-cold Fermi gas in an optical lattice
In this paper we study the density noise correlations of the two component
Fermi gas in optical lattices. Three different type of phases, the BCS-state
(Bardeen, Cooper, and Schieffer), the FFLO-state (Fulde, Ferrel, Larkin, and
Ovchinnikov), and BP (breach pair) state, are considered. We show how these
states differ in their noise correlations. The noise correlations are
calculated not only at zero temperature, but also at non-zero temperatures
paying particular attention to how much the finite temperature effects might
complicate the detection of different phases. Since one-dimensional systems
have been shown to be very promising candidates to observe FFLO states, we
apply our results also to the computation of correlation signals in a
one-dimensional lattice. We find that the density noise correlations reveal
important information about the structure of the underlying order parameter as
well as about the quasiparticle dispersions.Comment: 25 pages, 11 figures. Some figures are updated and text has been
modifie
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