726 research outputs found
Multi-patch model for transport properties of cuprate superconductors
A number of normal state transport properties of cuprate superconductors are
analyzed in detail using the Boltzmann equation. The momentum dependence of the
electronic structure and the strong momentum anisotropy of the electronic
scattering are included in a phenomenological way via a multi-patch model. The
Brillouin zone and the Fermi surface are divided in regions where scattering
between the electrons is strong and the Fermi velocity is low (hot patches) and
in regions where the scattering is weak and the Fermi velocity is large (cold
patches). We present several motivations for this phenomenology starting from
various microscopic approaches. A solution of the Boltzmann equation in the
case of N patches is obtained and an expression for the distribution function
away from equilibrium is given. Within this framework, and limiting our
analysis to the two patches case, the temperature dependence of resistivity,
thermoelectric power, Hall angle, magnetoresistance and thermal Hall
conductivity are studied in a systematic way analyzing the role of the patch
geometry and the temperature dependence of the scattering rates. In the case of
Bi-based cuprates, using ARPES data for the electronic structure, and assuming
an inter-patch scattering between hot and cold states with a linear temperature
dependence, a reasonable agreement with the available experiments is obtained.Comment: 18 pages, 18 figures, to be published on Eur. Phys. J.
Landau Theory of the Finite Temperature Mott Transition
In the context of the dynamical mean-field theory of the Hubbard model, we
identify microscopically an order parameter for the finite temperature Mott
endpoint. We derive a Landau functional of the order parameter. We then use the
order parameter theory to elucidate the singular behavior of various physical
quantities which are experimentally accessible.Comment: 4 pages, 2 figure
Strong Coupling Theory for Interacting Lattice Models
We develop a strong coupling approach for a general lattice problem. We argue
that this strong coupling perspective represents the natural framework for a
generalization of the dynamical mean field theory (DMFT). The main result of
this analysis is twofold: 1) It provides the tools for a unified treatment of
any non-local contribution to the Hamiltonian. Within our scheme, non-local
terms such as hopping terms, spin-spin interactions, or non-local Coulomb
interactions are treated on equal footing. 2) By performing a detailed
strong-coupling analysis of a generalized lattice problem, we establish the
basis for possible clean and systematic extensions beyond DMFT. To this end, we
study the problem using three different perspectives. First, we develop a
generalized expansion around the atomic limit in terms of the coupling
constants for the non-local contributions to the Hamiltonian. By analyzing the
diagrammatics associated with this expansion, we establish the equations for a
generalized dynamical mean-field theory (G-DMFT). Second, we formulate the
theory in terms of a generalized strong coupling version of the Baym-Kadanoff
functional. Third, following Pairault, Senechal, and Tremblay, we present our
scheme in the language of a perturbation theory for canonical fermionic and
bosonic fields and we establish the interpretation of various strong coupling
quantities within a standard perturbative picture.Comment: Revised Version, 17 pages, 5 figure
Interplane charge dynamics in a valence-bond dynamical mean-field theory of cuprate superconductors
We present calculations of the interplane charge dynamics in the normal state
of cuprate superconductors within the valence-bond dynamical mean-field theory.
We show that by varying the hole doping, the c-axis optical conductivity and
resistivity dramatically change character, going from metallic-like at large
doping to insulating-like at low-doping. We establish a clear connection
between the behavior of the c-axis optical and transport properties and the
destruction of coherent quasiparticles as the pseudogap opens in the antinodal
region of the Brillouin zone at low doping. We show that our results are in
good agreement with spectroscopic and optical experiments.Comment: 5 pages, 3 figure
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
Understanding the Heavy Fermion Phenomenology from Microscopic Model
We solve the 3D periodic Anderson model via two impurity DMFT. We obtain the
temperature v.s. hybridization phase diagram. In approaching the quantum
critical point (QCP) both the Neel and lattice Kondo temperatures decrease and
they do not cross at the lowest temperature we reached. While strong
ferromagnetic spin fluctuation on the Kondo side is observed, our result
indicates the critical static spin susceptibility is local in space at the QCP.
We observe in the crossover region logarithmic temperature dependence in the
specific heat coefficient and spin susceptibility
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