462 research outputs found
Electronic charge reconstruction of doped Mott insulators in multilayered nanostructures
Dynamical mean-field theory is employed to calculate the electronic charge
reconstruction of multilayered inhomogeneous devices composed of semi-infinite
metallic lead layers sandwiching barrier planes of a strongly correlated
material (that can be tuned through the metal-insulator Mott transition). The
main focus is on barriers that are doped Mott insulators, and how the
electronic charge reconstruction can create well-defined Mott insulating
regions in a device whose thickness is governed by intrinsic materials
properties, and hence may be able to be reproducibly made.Comment: 9 pages, 8 figure
Competition between electron-phonon attraction and weak Coulomb repulsion
The Holstein-Hubbard model is examined in the limit of infinite dimensions.
Conventional folklore states that charge-density-wave (CDW) order is more
strongly affected by Coulomb repulsion than superconducting order because of
the pseudopotential effect. We find that both incommensurate CDW and
superconducting phases are stabilized by the Coulomb repulsion, but,
surprisingly, the commensurate CDW transition temperature is more robust than
the superconducting transition temperature. This puzzling feature is resolved
by a detailed analysis of perturbation theory.Comment: 13 pages in ReVTex including 3 encapsulated postscript files
(embedded in the text). The encapsulated postscript files are compressed and
uuencoded after the TeX file
The anharmonic electron-phonon problem
The anharmonic electron-phonon problem is solved in the infinite-dimensional
limit using quantum Monte Carlo simulation. Charge-density-wave order is seen
to remain at half filling even though the anharmonicity removes the
particle-hole symmetry (and hence the nesting instability) of the model.
Superconductivity is strongly favored away from half filling (relative to the
charge-density-wave order) but the anharmonicity does not enhance transition
temperatures over the maximal values found in the harmonic limit.Comment: 5 pages typeset in ReVTeX. Four encapsulated postscript files
include
Inhomogeneous spectral moment sum rules for the retarded Green function and self-energy of strongly correlated electrons or ultracold fermionic atoms in optical lattices
Spectral moment sum rules are presented for the inhomogeneous many-body
problem described by the fermionic Falicov-Kimball or Hubbard models. These
local sum rules allow for arbitrary hoppings, site energies, and interactions.
They can be employed to quantify the accuracy of numerical solutions to the
inhomogeneous many-body problem like strongly correlated multilayered devices,
ultracold atoms in an optical lattice with a trap potential, strongly
correlated systems that are disordered, or systems with nontrivial spatial
ordering like a charge density wave or a spin density wave. We also show how
the spectral moment sum rules determine the asymptotic behavior of the Green
function, self-energy, and dynamical mean field, when applied to the dynamical
mean-field theory solution of the many body problem. In particular, we
illustrate in detail how one can dramatically reduce the number of Matsubara
frequencies needed to solve the Falicov-Kimball model, while still retaining
high precision, and we sketch how one can incorporate these results into
Hirsch-Fye quantum Monte Carlo solvers for the Hubbard (or more complicated)
models. Since the solution of inhomogeneous problems is significantly more time
consuming than periodic systems, efficient use of these sum rules can provide a
dramatic speed up in the computational time required to solve the many-body
problem. We also discuss how these sum rules behave in nonequilibrium
situations as well, where the Hamiltonian has explicit time dependence due to a
driving field or due to the time-dependent change of a parameter like the
interaction strength or the origin of the trap potential.Comment: (28 pages, 6 figures, ReVTeX) Paper updated to correct equations 11,
24, and 2
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