146 research outputs found
Electron Energy Loss Spectroscopy of strongly correlated systems in infinite dimensions
We study the electron-energy loss spectra of strongly correlated electronic
systems doped away from half-filling using dynamical mean-field theory
(). The formalism can be used to study the loss spectra in the
optical () limit, where it is simply related to the optical
response, and hence can be computed in an approximation-free way in .
We apply the general formalism to the one-band Hubbard model off , with
inclusion of site-diagonal randomness to simulate effects of doping. The
interplay between the coherence induced plasmon feature and the
incoherence-induced high energy continuum is explained in terms of the
evolution in the local spectral density upon hole doping. Inclusion of static
disorder is shown to result in qualitative changes in the low-energy features,
in particular, to the overdamping of the plasmon feature, resulting in a
completely incoherent response. The calculated EELS lineshapes are compared to
experimentally observed EELS spectra for the normal state of the high-
materials near optimal doping and good qualitative agreement is found.Comment: 5 pages, 3 figures, submitted to J. Phys. - Cond. Mat
Theory of Magnetic Fluctuations in Iron Pnictides
Magnetic fluctuations in an unconventional superconductor (U-SC) can
distinguish between distinct proposals for the symmetry of the order parameter.
Motivated thereby, we undertake a study magnetic fluctuations in Iron
pnictides, tracking their evolution from the incoherent normal, pseudogapped
metal, to the U-SC state. Within our proposal of extended-s-plus s_{xy} inplane
gap with proximity-induced out-of-plane line nodes, (i) we describe the
evolution of the spin-lattice relaxation rate, from a non-Korringa form in the
normal state, to a power-law form in the U-SC in good agreement with
experiment, and (ii) we predict a sharp resonance in the U-SC state along
(\pi,\pi), but not along (\pi/2,0), along with modulated c-axis intensity in
inelastic neutron scattering work as a specific and testable manifestation of
our proposal.Comment: 4 pages, 3 figures - to be submitted to PR
Quantum Critical Phase and Lifshitz Transition in an Extended Periodic Anderson Model
We study the quantum phase transition in -electron systems as a quantum
Lifshitz transition driven by selective Mott localization in a realistic
extended Anderson lattice model. Using DMFT, we find that a quantum critical
{\it phase} with anomalous scaling separates a heavy Landau-Fermi
liquid from ordered phase(s). Fermi surface reconstruction occurs via the
interplay between, and penetration of the Green function zeros to the poles,
leading to violation of Luttinger's theorem in the selective-Mott phase . We
show how this naturally leads to scale-invariant responses in transport. Our
work is represents a specific (DMFT) realization of the hidden-FL and FL
theories, and holds promise for study of "strange" metal phases in quantum
matter.Comment: 8 pages,5 figure
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