218 research outputs found
Electronic Raman scattering in correlated materials: exact treatment of nonresonant, mixed, and resonant scattering with dynamical mean field theory
We solve for the electronic Raman scattering response functions on an
infinite-dimensional hypercubic lattice employing dynamical mean field theory.
This contribution extends previous work on the nonresonant response to include
the mixed and resonant contributions. We focus our attention on the spinless
Falicov-Kimball model, where the problem can be solved exactly, and the system
can be tuned to go through a Mott-Hubbard-like metal-insulator transition.
Resonant effects vary in different scattering geometries, corresponding to the
symmetries of the charge excitations scattered by the light. We do find that
the Raman response is large near the double resonance, where the transfered
frequency is close to the incident photon frequency. We also find a joint
resonance of both the charge-transfer peak and the low-energy peak when the
incident photon frequency is on the order of the interaction strength. In
general, the resonance effects can create order of magnitude (or more)
enhancements of features in the nonresonant response, especially when the
incident photon frequency is somewhat larger than the frequency of the
nonresonant feature. Finally, we find that the resonant effects also exhibit
isosbestic behavior, even in the A1g and B2g sectors, and it is most prominent
when the incident photon frequency is on the order of the interaction energy.Comment: (20 pages, 13 figures
Inelastic X-ray scattering in correlated (Mott) insulators
We calculate the inelastic light scattering from X-rays, which allows the
photon to transfer both energy and momentum to the strongly correlated charge
excitations. We find that the charge transfer peak and the low energy peak both
broaden and disperse through the Brillouin zone similar to what is seen in
experiments in materials like Ca_2 Cu O_2 Cl_2.Comment: 5 pages Revtex4, 6 figure
Nonresonant Raman and inelastic X-ray scattering in the charge-density-wave phase of the spinless Falicov-Kimball model
Nonresonant inelastic light and X-ray scattering is investigated for the
spinless Falicov-Kimball model on an infinite-dimensional hypercubic lattice
with a charge-density-wave phase at half filling. The many-body density of
states (DOS) is found for different values of the Coulomb repulsion ,
ranging from a dirty metal to a Mott insulator. At zero temperature, the charge
gap is exactly equal to ; increasing the temperature rapidly fills the gap
with subgap states. The nonresonant response function for Raman and inelastic
X-ray scattering shows peaks connected with transitions over the gap and
transitions that involve subgap states. In the case of X-ray scattering (when
both energy and momentum are transferred), the response function illustrates
features of dynamical screening (vertex corrections) in the different
(nonresonant) symmetry channels ( and ). We also derive
and verify the first moment sum rules for the (nonresonant) Raman and inelastic
X-ray response functions.Comment: 19 pages, 17 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
Total electronic Raman scattering in the charge-density-wave phase of the spinless Falicov-Kimball model
The total electronic Raman scattering spectrum, including the nonresonant,
mixed and resonant components, is determined for the charge-density-wave (CDW)
phase of the spinless Falicov-Kimball model at half filling within dynamical
mean-field theory. Its frequency dependence is investigated for different
values of the energy of the incident photons. The spectra reflect the different
structures in the density of states and how they are modified by screening and
resonance effects. The calculations are performed for the , and symmetries (which are typically examined in experiment).
Our results for the resonance effects of the Raman spectra, found by tuning the
energy of the incident photons, give information about the many-body charge
dynamics of the CDW-ordered phase.Comment: 8 pages, contribution to the proceedings of the 3rd Conference
"Statistical Physics: Modern Trends and Applications", June 23-25, 2009 Lviv,
Ukrain
Lower bound for the segregation energy in the Falicov-Kimball model
In this work, a lower bound for the ground state energy of the
Falicov-Kimball model for intermediate densities is derived. The explicit
derivation is important in the proof of the conjecture of segregation of the
two kinds of fermions in the Falicov-Kimball model, for sufficiently large
interactions. This bound is given by a bulk term, plus a term proportional to
the boundary of the region devoid of classical particles. A detailed proof is
presented for density n=1/2, where the coefficient 10^(-13) is obtained for the
boundary term, in two dimensions. With suitable modifications the method can
also be used to obtain a coefficient for all densities.Comment: 8 pages, 2 figure
Resonant Enhancement of Inelastic Light Scattering in Strongly Correlated Materials
We use dynamical mean field theory to find an exact solution for inelastic
light scattering in strongly correlated materials such as those near a
quantum-critical metal-insulator transition. We evaluate the results for
(Raman) scattering and find that resonant effects can be quite
large, and yield a triple resonance, a significant enhancement of nonresonant
scattering peaks, a joint resonance of both peaks when the incident photon
frequency is on the order of , and the appearance of an isosbestic point in
all symmetry channels for an intermediate range of incident photon frequencies.Comment: 5 pages RevTex, 4 Figures ep
Optical sum rules that relate to the potential energy of strongly correlated systems
A class of sum rules for inelastic light scattering is developed. We show
that the first moment of the non-resonant response provides information about
the potential energy in strongly correlated systems. The polarization
dependence of the sum rules provide information about the electronic
excitations in different regions of the Brillouin zone. We determine the sum
rule for the Falicov-Kimball model, which possesses a metal-insulator
transition, and compare our results to the light scattering experiments in
SmB_6.Comment: (5 pages, 3 figures, typeset in ReVTeX
F-electron spectral function of the Falicov-Kimball model in infinite dimensions: the half-filled case
The f-electron spectral function of the Falicov-Kimball model is calculated
via a Keldysh-based many-body formalism originally developed by Brandt and
Urbanek. We provide results for both the Bethe lattice and the hypercubic
lattice at half filling. Since the numerical computations are quite sensitive
to the discretization along the Kadanoff-Baym contour and to the maximum cutoff
in time that is employed, we analyze the accuracy of the results using a
variety of different moment sum-rules and spectral formulas. We find that the
f-electron spectral function has interesting temperature dependence becoming a
narrow single-peaked function for small U and developing a gap, with two
broader peaks for large U.Comment: (13 pages, 11 figures, typeset in RevTex 4
- …