23 research outputs found
Spectral microscopic mechanisms and quantum phase transitions in a 1D correlated problem
In this paper we study the dominant microscopic processes that generate
nearly the whole one-electron removal and addition spectral weight of the
one-dimensional Hubbard model for all values of the on-site repulsion . We
find that for the doped Mott-Hubbard insulator there is a competition between
the microscopic processes that generate the one-electron upper-Hubbard band
spectral-weight distributions of the Mott-Hubbard insulating phase and
finite-doping-concentration metallic phase, respectively. The spectral-weight
distributions generated by the non-perturbative processes studied here are
shown elsewhere to agree quantitatively for the whole momentum and energy
bandwidth with the peak dispersions observed by angle-resolved photoelectron
spectroscopy in quasi-one-dimensional compounds.Comment: 18 pages, 2 figure
General spectral function expressions of a 1D correlated model
We introduce a method that allows the evaluation of general expressions for
the spectral functions of the one-dimensional Hubbard model for all values of
the on-site electronic repulsion U. The spectral weights are expressed in terms
of pseudofermion operators such that the spectral functions can be written as a
convolution of pseudofermion dynamical correlation functions. Our results are
valid for all finite energy and momentum values and are used elsewhere in the
study of the unusual finite-energy properties of quasi-one-dimensional
compounds and the new quantum systems of ultra-cold fermionic atoms on an
optical lattice.Comment: 25 pages, no figure
Superconductivity Driven by Chain Coupling and Electronic Correlations
We present an analysis of a system of weakly coupled Hubbard chains based on
combining an exact study of spectral functions of the uncoupled chain system
with a renormalization group method for the coupled chains. For low values of
the onsite repulsion and of the doping , the leading instability is
towards a superconducting state. The process includes excited states above a
small correlation pseudogap. Similar features appear in extended Hubbard models
in the vicinity of commensurate fillings. Our theoretical predictions are
consistent with the phase diagram observed in the (TMTTF)X and (TMTSF)X
series of organic compounds.Comment: 7 pages, 2 figure
Dynamical Functions of a 1D Correlated Quantum Liquid
We extend to initial ground states with zero spin density m = 0 the
expressions provided by the pseudofermion dynamical theory (PDT) for the
finite-energy one- and two-electron spectral-weight distributions of a
one-dimensional (1D) correlated metal with on-site particle-particle repulsion.
The spectral-function expressions derived in this paper were used in recent
successful and detailed theoretical studies of the finite-energy singular
features in photoemission of the organic compound
tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) metallic phase. Our
studies take into account spectral contributions from types of microscopic
processes that do not occur for finite values of the spin density. Expressions
for the spectral functions in the vicinity of the singular border lines which
also appear in the TTF- TCNQ spectral-weight distribution are derived. In
addition, the PDT expressions are generalized for electronic densities in the
vicinity of half filling. Further details on the processes involved in the
applications to TTF-TCNQ are reported. Our results are useful for the further
understanding of the unusual spectral properties observed in low-dimensional
organic metals and also provide expressions for the one- and two-atom spectral
functions of a correlated quantum system of ultracold fermionic atoms in a 1D
optical lattice with on-site two-atom repulsion
The TTF finite-energy spectral features in photoemission of TTF-TCNQ: The Hubbard-chain description
A dynamical theory which accounts for all microscopic one-electron processes
is used to study the spectral function of the 1D Hubbard model for the whole
-plane, beyond previous studies which focused on the weight
distribution in the vicinity of the singular branch lines only. While our
predictions agree with those of the latter studies concerning the
tetracyanoquinodimethane (TCNQ) related singular features in photoemission of
the organic compound tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ)
metallic phase, the generalized theory also leads to quantitative agreement
concerning the tetrathiafulvalene (TTF) related finite-energy spectral
features, which are found to correspond to a value of the on-site repulsion
larger than for TCNQ. Our study reveals the microscopic mechanisms behind the
unusual spectral features of TTF-TCNQ and provides a good overall description
of those features for the whole -plane.Comment: To appear in Journal of Physics: Condensed Matte
Scattering mechanisms and spectral properties of the one-dimensional Hubbard model
It is found that the finite-energy spectral properties of the one-dimensional
Hubbard model are controlled by the scattering of charged -spin-zero
-holon composite objects, spin-zero -spinon composite objects, and
charged -spin-less and spin-less objects, rather than by the scattering
of independent -spin 1/2 holons and spin 1/2 spinons. Here . The corresponding matrix is calculated and its relation to the
spectral properties is clarified.Comment: 8 pages, no figure
One-Electron Singular Branch Lines of the Hubbard Chain
The momentum and energy dependence of the weight distribution in the vicinity
of the one-electron spectral-function singular branch lines of the 1D Hubbard
model is studied for all values of the electronic density and on-site repulsion
. To achieve this goal we use the recently introduced pseudofermion
dynamical theory. Our predictions agree quantitatively for the whole momentum
and energy bandwidth with the peak dispersions observed by angle-resolved
photoelectron spectroscopy in the quasi-1D organic conductor TTF-TCNQ.Comment: Replaced with shortened version; 4 figure