136 research outputs found
Heavy-fermion and spin-liquid behavior in a Kondo lattice with magnetic frustration
We study the competition between the Kondo effect and frustrating exchange
interactions in a Kondo-lattice model within a large- dynamical
mean-field theory. We find a T=0 phase transition between a heavy Fermi-liquid
and a spin-liquid for a critical value of the exchange , the
single-impurity Kondo temperature. Close to the critical point, the Fermi
liquid coherence scale is strongly reduced and the effective mass
strongly enhanced. The regime is characterized by spin-liquid
magnetic correlations and non-Fermi-liquid properties. It is suggested that
magnetic frustration is a general mechanism which is essential to explain the
large effective mass of some metallic compounds such as LiVO.Comment: 7 pages, 1 figure. Late
Semiclassical Analysis of Extended Dynamical Mean Field Equations
The extended Dynamical Mean Field Equations (EDMFT) are analyzed using
semiclassical methods for a model describing an interacting fermi-bose system.
We compare the semiclassical approach with the exact QMC (Quantum Montecarlo)
method. We found the transition to an ordered state to be of the first order
for any dimension below four.Comment: RevTex, 39 pages, 16 figures; Appendix C added, typos correcte
Charge and spin density wave ordering transitions in strongly correlated metals
We study the quantum transition from a strongly correlated metal, with heavy
fermionic quasiparticles, to a metal with commensurate charge or spin density
wave order. To this end, we introduce and numerically analyze a large
dimensionality model of Ising spins in a transverse field, coupled to two
species of fermions; the analysis borrows heavily from recent progress in the
solution of the Hubbard model in large dimensions. At low energies, the Ising
order parameter fluctuations are characterized by the critical exponent , while above an energy scale, , there is a crossover to criticality. We show that is of the order of the width of the
heavy quasiparticle band, and can be made arbitrarily small for a correlated
metal close to a Mott-Hubbard insulator. Therefore, such a correlated metal has
a significant intermediate energy range of behavior, a single
particle spectrum with a narrow quasiparticle band, and well-formed analogs of
the lower and upper Hubbard bands; we suggest that these features are
intimately related in general.Comment: 14 pages, REVTEX 3.0, 2 postscript figure
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