39 research outputs found
Spectral density of an interacting dot coupled indirectly to conducting leads
We study the spectral density of electrons rho in an interacting quantum dot
(QD) with a hybridization lambda to a non-interacting QD, which in turn is
coupled to a non-interacting conduction band. The system corresponds to an
impurity Anderson model in which the conduction band has a Lorentzian density
of states of width Delta2.
We solved the model using perturbation theory in the Coulomb repulsion U
(PTU) up to second order and a slave-boson mean-field approximation (SBMFA).
The PTU works surprisingly well near the exactly solvable limit Delta2 -> 0.
For fixed U and large enough lambda or small enough Delta2, the Kondo peak in
rho(omega) splits into two peaks. This splitting can be understood in terms of
weakly interacting quasiparticles. Before the splitting takes place the
universal properties of the model in the Kondo regime are lost. Using the
SBMFA, simple analytical expressions for the occurrence of split peaks are
obtained. For small or moderate Delta2, the side bands of rho(omega) have the
form of narrow resonances, that were missed in previous studies using the
numerical renormalization group. This technique also has shortcomings for
describing properly the split Kondo peaks. As the temperature is increased, the
intensity of the split Kondo peaks decreases, but it is not completely
suppressed at high temperatures.Comment: 13 pages, 13 figures, accepted in Phys. Rev.
Low-energy models for correlated materials: bandwidth renormalization from Coulombic screening
We provide a prescription for constructing Hamiltonians representing the low
energy physics of correlated electron materials with dynamically screened
Coulomb interactions. The key feature is a renormalization of the hopping and
hybridization parameters by the processes that lead to the dynamical screening.
The renormalization is shown to be non-negligible for various classes of
correlated electron materials. The bandwidth reduction effect is necessary for
connecting models to materials behavior and for making quantitative predictions
for low-energy properties of solids.Comment: 4 pages, 2 figure
Dynamical screening in strongly correlated metal SrVO3
The consequences of dynamical screening of Coulomb interaction among
correlated electrons in realistic materials have not been widely considered
before. In this letter we try to incorporate a frequency dependent Coulomb
interaction into the state-of-the-art ab initio electronic structure computing
framework of local density approximation plus dynamical mean-field theory, and
then choose SrVO3 as a prototype material to demonstrate the importance of
dynamical screening effect. It is shown to renormalise the spectral weight near
the Fermi level, to increase the effective mass, and to suppress the t2g
quasiparticle band width apparently. The calculated results are in accordance
with very recent angle-resolved photoemission spectroscopy experiments and Bose
factor ansatz calculations.Comment: 6 pages, 4 figures. arXiv admin note: text overlap with
arXiv:1107.312
Long-Range coulomb interactions in surface systems: a first-Principles description within self-Consistently combined GW and dynamical mean-Field theory
Systems of adatoms on semiconductor surfaces display competing ground states and exotic spectral properties typical of two-dimensional correlated electron materials which are dominated by a complex interplay of spin and charge degrees of freedom. We report a fully ab initio derivation of low-energy Hamiltonians for the adatom systems Si(111):X, with X=Sn, Si, C, Pb, that we solve within self-consistently combined GW and dynamical mean-field theory. Calculated photoemission spectra are in agreement with available experimental data. We rationalize experimentally observed trends from Mott physics toward charge ordering along the series as resulting from substantial long-range interactions