3,351 research outputs found
Low-energy kink in the nodal dispersion of copper-oxide superconductors: Insights from Dynamical Mean Field Theory
Motivated by the observation in copper-oxide high-temperature
superconductors, we investigate the appearance of kinks in the electronic
dispersion due to coupling to phonons for a system with strong electronic
repulsion. We study a Hubbard model supplemented by an electron-phonon coupling
of Holstein type within Dynamical Mean Field Theory (DMFT) utilizing Numerical
Renormalization Group as impurity solver. Paramagnetic DMFT solutions in the
presence of large repulsion show a kink only for large values of the
electron-phonon coupling or large doping and, contrary to the
conventional electron-phonon theory, the position of such a kink can be shifted
to energies larger than the renormalized phonon frequency . When
including antiferromagnetic correlations we find a stronger effect of the
electron-phonon interaction on the electronic dispersion due to a cooperative
effect and a visible kink at , even for smaller . Our
results provide a scenario of a kink position increasing with doping, which
could be related to recent photoemission experiments on Bi-based cuprates.Comment: 10 pages, 10 figures; additional referene
Relevance of phonon dynamics in strongly correlated systems coupled to phonons: A Dynamical Mean Field Theory analysis
The properties of the electron-phonon interaction in the presence of a
sizable electronic repulsion at finite doping are studied by investigating the
metallic phase of the Hubbard-Holstein model with Dynamical Mean Field Theory.
Analyzing the quasiparticle weight at finite doping, we find that a large
Coulomb repulsion reduces the effect of electron-phonon coupling at low-energy,
while this reduction is not present at high energy. The renormalization of the
electron-phonon coupling induced by the Hubbard repul sion depends in a
surprisingly strong and non-trivial way on the phonon frequency. Our results
suggest that phonon might affect differently high-energy and low-energy
properties and this, together with the effect of phonon dynamics, should be
carefully taken into account when the effects of the electron-phonon
interaction in a strongly correlated system, like the superconducting cuprates,
are discussed.Comment: 10 pages, 7 figures - revised version with minor change
Truth and Reconciliation Commissions: A Needed Force in Alaska?
Truth and Reconciliation Commissions are official, temporary bodies used for communities to come to terms with past violence, promote education and awareness of historic trauma, and to provide recognition and closure for victims and successors. By bringing past issues to light, such commissions promote healing and allow these communities to move forward. Although the Commission on Truth and Reconciliation in South Africa after the Apartheid-era is best known, several similar commissions have been established throughout the globe and within the United States. This paper compares commissions from South Africa, El Salvador, South Korea, and Canada with those that have been established in the United States to examine whether such a commission would be useful in Alaska to address current social problems in the state
Double Exchange model for nanoscopic clusters
We solve the double exchange model on nanoscopic clusters exactly, and
specifically consider a six-site benzene-like nanocluster. This simple model is
an ideal testbed for studying magnetism in nanoclusters and for validating
approximations such as the dynamical mean field theory (DMFT). Non-local
correlations arise between neighboring localized spins due to the Hund's rule
coupling, favoring a short-range magnetic order of ferro- or antiferromagnetic
type. For a geometry with more neighboring sites or a sufficiently strong
hybridization between leads and the nanocluster, these non-local correlations
are less relevant, and DMFT can be applied reliably.Comment: 9 pages, 9 figures, 1 tabl
Transient model of hydrogen/oxygen reactor
Numerical analysis of effects of transient response in catalytic ignition system to promote hydrogen-oxygen combustio
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