5,697 research outputs found
Spectral properties in the charge density wave phase of the half-filled Falicov-Kimball Model
We study the spectral properties of charge density wave (CDW) phase of the
half-filled spinless Falicov-Kimball model within the framework of the
Dynamical Mean Field Theory. We present detailed results for the spectral
function in the CDW phase as function of temperature and . We show how the
proximity of the non-fermi liquid phase affects the CDW phase, and show that
there is a region in the phase diagram where we get a CDW phase without a gap
in the spectral function. This is a radical deviation from the mean-field
prediction where the gap is proportional to the order parameter
Classification cards applied to team and individual learning.
Thesis (Ed.M.)--Boston Universit
Dynamical Mean-Field Theory - from Quantum Impurity Physics to Lattice Problems
Since the first investigation of the Hubbard model in the limit of infinite
dimensions by Metzner and Vollhardt, dynamical mean-field theory (DMFT) has
become a very powerful tool for the investigation of lattice models of
correlated electrons. In DMFT the lattice model is mapped on an effective
quantum impurity model in a bath which has to be determined self-consistently.
This approach lead to a significant progress in our understanding of typical
correlation problems such as the Mott transition; furthermore, the combination
of DMFT with ab-initio methods now allows for a realistic treatment of
correlated materials. The focus of these lecture notes is on the relation
between quantum impurity physics and the physics of lattice models within DMFT.
Issues such as the observability of impurity quantum phase transitions in the
corresponding lattice models are discussed in detail.Comment: 18 pages, 5 figures, invited paper for the Proceedings of the "3rd
International Summer School on Strongly Correlated Systems, Debrecen, 2004
Sound Velocity Anomaly at the Mott Transition: application to organic conductors and V2O3
Close to the Mott transition, lattice degrees of freedom react to the
softening of electron degrees of freedom. This results in a change of lattice
spacing, a diverging compressibility and a critical anomaly of the sound
velocity. These effects are investigated within a simple model, in the
framework of dynamical mean-field theory. The results compare favorably to
recent experiments on the layered organic \kappa-(BEDT-TTF)_2Cu[N(CN)_2]Cl
conductor . We predict that effects of a similar magnitude are expected for
V2O3, despite the much larger value of the elastic modulus of this material.Comment: New discussion of the relation between the sound-velocity and the
compressibility has been adde
Competing itinerant and localized states in strongly correlated BaVS
The electronic structure of the quasi-lowdimensional vanadium sulfide \bavs3
is investigated for the different phases above the magnetic ordering
temperature. By means of density functional theory and its combination with
dynamical-mean field theory, we follow the evolution of the relevant low-energy
electronic states on cooling. Hence we go in the metallic regime from the room
temperature hexagonal phase to the orthorhombic phase after the first
structural transition, and close with the monoclinic insulating phase below the
metal-insulator transition. Due to the low symmetry and expected intersite
correlations, the latter phase is treated within cellular dynamical mean-field
theory. It is generally discussed how the intriguing interplay between
band-structure and strong-correlation effects leads to the stabilization of the
various electronic phases with decreasing temperature.Comment: 12 pages, submitted to PR
Mott transition at large orbital degeneracy: dynamical mean-field theory
We study analytically the Mott transition of the N-orbital Hubbard model
using dynamical mean-field theory and a low-energy projection onto an effective
Kondo model. It is demonstrated that the critical interaction at which the
insulator appears (Uc1) and the one at which the metal becomes unstable (Uc2)
have different dependence on the number of orbitals as the latter becomes
large: Uc1 ~ \sqrt{N} while Uc2 ~ N. An exact analytical determination of the
critical coupling Uc2/N is obtained in the large-N limit. The metallic solution
close to this critical coupling has many similarities at low-energy with the
results of slave boson approximations, to which a comparison is made. We also
discuss how the critical temperature associated with the Mott critical endpoint
depends on the number of orbitals.Comment: 13 pages. Minor changes in V
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