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Title: Towards a deeper insight into strongly correlated electron systems- the symbiosis between experiment and theory

Publication Date:
Research Org.:
Ernest Orlando Lawrence Berkeley NationalLaboratory, Berkeley, CA (US)
Sponsoring Org.:
USDOE Director. Office of Science. Basic EnergySciences
OSTI Identifier:
Report Number(s):
R&D Project: 509201; BnR: KC0202020
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics: Condensed Matter; Journal Volume: 19; Related Information: Journal Publication Date: 2007
Country of Publication:
United States

Citation Formats

Fischer, Peter. Towards a deeper insight into strongly correlated electron systems- the symbiosis between experiment and theory. United States: N. p., 2007. Web. doi:10.1088/0953-8984/19/18/181002.
Fischer, Peter. Towards a deeper insight into strongly correlated electron systems- the symbiosis between experiment and theory. United States. doi:10.1088/0953-8984/19/18/181002.
Fischer, Peter. Thu . "Towards a deeper insight into strongly correlated electron systems- the symbiosis between experiment and theory". United States. doi:10.1088/0953-8984/19/18/181002.
title = {Towards a deeper insight into strongly correlated electron systems- the symbiosis between experiment and theory},
author = {Fischer, Peter},
abstractNote = {},
doi = {10.1088/0953-8984/19/18/181002},
journal = {Journal of Physics: Condensed Matter},
number = ,
volume = 19,
place = {United States},
year = {Thu Mar 01 00:00:00 EST 2007},
month = {Thu Mar 01 00:00:00 EST 2007}
  • We compare the theoretical predictions for universal thermodynamics of a homogeneous, strongly correlated Fermi gas with the latest experimental measurements reported by the ENS group [S. Nascimbene et al., Nature (London) 463, 1057 (2010)] and the Tokyo group [M. Horikoshi et al., Science 327, 442 (2010)]. The theoretical results are obtained using two diagrammatic theories, together with a virial expansion theory combined with a Pade approximation. We find good agreement between theory and experiment. In particular, the virial expansion, using a Pade approximation up to third order, describes the experimental results extremely well down to the superfluid transition temperature, T{submore » c{approx}}0.16T{sub F}, where T{sub F} is the Fermi temperature. The comparison in this work complements our previous comparative study on the universal thermodynamics of a strongly correlated but trapped Fermi gas. The comparison also raises interesting issues about the unitary entropy and the applicability of the Pade approximation.« less
  • The orbital Kondo effect is treated in a model where, additional to the conduction band, there are localized orbitals close to the Fermi energy. If the hopping between the conduction band and the localized heavy orbitals depends on the occupation of the atomic orbitals in the conduction band, then orbital Kondo correlation occurs. The noncommutative nature of the coupling required for the Kondo effect is formally due to the form factors associated with the assisted hopping, which in the momentum representation depends on the momenta of the conduction electrons involved. The leading logarithmic vertex corrections are due to the localmore » Coulomb interaction between the electrons on the heavy orbital and in the conduction band. The renormalized vertex functions are obtained as a solution of a closed set of differential equations and they show power behavior. The amplitude of large renormalization is determined by an infrared cutoff due to finite energy and dispersion of the heavy particles. The enhanced assisted hopping rate results in mass enhancement and attractive interaction in the conduction band. The superconductivity transition temperature calculated is largest for the intermediate mass enhancement, [ital m][sup *]/[ital m][approx]2--3. For larger mass enhancement the small one-particle weight ([ital Z]) in the Green's function reduces the transition temperature, which may be characteristic for other models as well. The theory is developed for different one-dimensional and square-lattice models, but the applicability is not limited to them. In the one-dimensional case charge- and spin-density susceptibilities are also discussed. Good candidates for the heavy orbital are [ital f] bands in the heavy fermionic systems and nonbonding oxygen orbitals in high-temperature superconductors and different flatbands in the quasi-one-dimensional organic conductors.« less
  • Inspired by earlier work on the band-gap problem in insulators, we reexamine the treatment of strongly correlated Hubbard-type models within density-functional theory. In contrast to previous studies, the density is fully parametrized by occupation numbers {ital and} overlap of orbitals centered at neighboring atomic sites, as is the local potential by the hopping matrix. This corresponds to a good formal agreement between density-functional theory in real space and second quantization. It is shown that density-functional theory is formally applicable to such systems and the theoretical framework is provided. The question of noninteracting {ital v} representability is studied numerically for finitemore » one-dimnsional clusters, for which exact results are available, and qualitatively for infinite systems. This leads to the conclusion that the electron density corresponding to interacting systems of the type studied here is in fact {ital not} noninteracting {ital v} representable because the Kohn-Sham electrons are unable to reproduce the correlation-induced localization correctly.« less
  • A unified theory is developed for describing dynamic and static properties of strongly correlated charged-particle systems, such as a high-density electron liquid and a strongly turbulent plasma, for which the correlation (or fluctuation) energy is comparable in magnitude to the kinetic energy. Based on the microscopic Klimontovich formalism, a systematic renormalization of the single-particle propagators is carried out and vertex corrections arising from strong correlations are taken account of. The resulting theory is examined, and found to be satisfactory, in the light of a number of rigorous criteria, such as explicit inclusion of statistical modification effects in the single-particle orbits,more » dynamic modification of effective particle interactions brought about by strong correlations, frequency-moment sum rules of the dielectric response function, and reproduction of exact results known in the static properties of the electron liquid; the theory is thus valid for all wave numbers and frequencies. With the aid of a velocity-average approximation, we show that the result can be expressed in a simplified form which still satisfies those criteria. Its relation with the polarization potential model in the theory of condensed matter is thereby noted; explicit expressions for the scalar and vector polarization potentials, the wave-number-dependent effective mass, and the collisional contribution to the response function are obtained. (AIP)« less