3,025 research outputs found
Breakup of the Fermi surface near the Mott transition in low-dimensional systems
We investigate the Mott transition in weakly-coupled one-dimensional (1d)
fermionic chains. Using a generalization of Dynamic Mean Field Theory, we show
that the Mott gap is suppressed at some critical hopping . The
transition from the 1d insulator to a 2d metal proceeds through an intermediate
phase where the Fermi surface is broken into electron and hole pockets. The
quasiparticle spectral weight is strongly anisotropic along the Fermi surface,
both in the intermediate and metallic phases. We argue that such pockets would
look like `arcs' in photoemission experiments.Comment: REVTeX 4, 5 pages, 4 EPS figures. References added; problem with
figure 4 fixed; typos correcte
Low-energy models for correlated materials: bandwidth renormalization from Coulombic screening
We provide a prescription for constructing Hamiltonians representing the low
energy physics of correlated electron materials with dynamically screened
Coulomb interactions. The key feature is a renormalization of the hopping and
hybridization parameters by the processes that lead to the dynamical screening.
The renormalization is shown to be non-negligible for various classes of
correlated electron materials. The bandwidth reduction effect is necessary for
connecting models to materials behavior and for making quantitative predictions
for low-energy properties of solids.Comment: 4 pages, 2 figure
A supersymmetric model for triggering Supernova Ia in isolated white dwarfs
We propose a model for supernovae Ia explosions based on a phase transition
to a supersymmetric state which becomes the active trigger for the deflagration
starting the explosion in an isolated sub-Chandrasekhar white dwarf star. With
two free parameters we fit the rate and several properties of type Ia
supernovae and address the gap in the supermassive black hole mass
distribution. One parameter is a critical density fit to about
g/cc while the other has the units of a space time volume and is found to be of
order Gyr where is the earth radius. The model involves
a phase transition to an exact supersymmetry in a small core of a dense star.Comment: 20 pages, 5 figures, expanded version to be published in Physical
Review
Correlation between Compact Radio Quasars and Ultra-High Energy Cosmic Rays
Some proposals to account for the highest energy cosmic rays predict that
they should point to their sources. We study the five highest energy events
(E>10^20 eV) and find they are all aligned with compact, radio-loud quasars.
The probability that these alignments are coincidental is 0.005, given the
accuracy of the position measurements and the rarity of such sources. The
source quasars have redshifts between 0.3 and 2.2. If the correlation pointed
out here is confirmed by further data, the primary must be a new hadron or one
produced by a novel mechanism.Comment: 8 pages, 3 tables, revtex. with some versions of latex it's necessary
to break out the tables and latex them separately using article.sty rather
than revtex.st
The alpha-gamma transition of Cerium is entropy-driven
We emphasize, on the basis of experimental data and theoretical calculations,
that the entropic stabilization of the gamma-phase is the main driving force of
the alpha-gamma transition of cerium in a wide temperature range below the
critical point. Using a formulation of the total energy as a functional of the
local density and of the f-orbital local Green's functions, we perform
dynamical mean-field theory calculations within a new implementation based on
the multiple LMTO method, which allows to include semi-core states. Our results
are consistent with the experimental energy differences and with the
qualitative picture of an entropy-driven transition, while also confirming the
appearance of a stabilization energy of the alpha phase as the quasiparticle
Kondo resonance develops.Comment: 5 pages, 6 figure
Is the Mott transition relevant to f-electron metals ?
We study how a finite hybridization between a narrow correlated band and a
wide conduction band affects the Mott transition. At zero temperature, the
hybridization is found to be a relevant perturbation, so that the Mott
transition is suppressed by Kondo screening. In contrast, a first-order
transition remains at finite temperature, separating a local moment phase and a
Kondo- screened phase. The first-order transition line terminates in two
critical endpoints. Implications for experiments on f-electron materials such
as the Cerium alloy CeLaTh are discussed.Comment: 5 pages, 3 figure
Self-consistency over the charge-density in dynamical mean-field theory: a linear muffin-tin implementation and some physical implications
We present a simple implementation of the dynamical mean-field theory
approach to the electronic structure of strongly correlated materials. This
implementation achieves full self-consistency over the charge density, taking
into account correlation-induced changes to the total charge density and
effective Kohn-Sham Hamiltonian. A linear muffin-tin orbital basis-set is used,
and the charge density is computed from moments of the many body
momentum-distribution matrix. The calculation of the total energy is also
considered, with a proper treatment of high-frequency tails of the Green's
function and self-energy. The method is illustrated on two materials with
well-localized 4f electrons, insulating cerium sesquioxide Ce2O3 and the
gamma-phase of metallic cerium, using the Hubbard-I approximation to the
dynamical mean-field self-energy. The momentum-integrated spectral function and
momentum-resolved dispersion of the Hubbard bands are calculated, as well as
the volume-dependence of the total energy. We show that full self-consistency
over the charge density, taking into account its modification by strong
correlations, can be important for the computation of both thermodynamical and
spectral properties, particularly in the case of the oxide material.Comment: 20 pages, 6 figures (submitted in The Physical Review B
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