1,170 research outputs found
Scaling Between Periodic Anderson and Kondo Lattice Models
Continuous-Time Quantum Monte Carlo (CT-QMC) method combined with Dynamical
Mean Field Theory (DMFT) is used to calculate both Periodic Anderson Model
(PAM) and Kondo Lattice Model (KLM). Different parameter sets of both models
are connected by the Schrieffer-Wolff transformation. For degeneracy N=2, a
special particle-hole symmetric case of PAM at half filling which always fixes
one electron per impurity site is compared with the results of the KLM. We find
a good mapping between PAM and KLM in the limit of large on-site Hubbard
interaction U for different properties like self-energy, quasiparticle residue
and susceptibility. This allows us to extract quasiparticle mass
renormalizations for the f electrons directly from KLM. The method is further
applied to higher degenerate case and to realsitic heavy fermion system CeRhIn5
in which the estimate of the Sommerfeld coefficient is proven to be close to
the experimental value
Self-Consistent Perturbation Theory for Thermodynamics of Magnetic Impurity Systems
Integral equations for thermodynamic quantities are derived in the framework
of the non-crossing approximation (NCA). Entropy and specific heat of 4f
contribution are calculated without numerical differentiations of thermodynamic
potential. The formulation is applied to systems such as PrFe4P12 with
singlet-triplet crystalline electric field (CEF) levels.Comment: 3 pages, 2 figures, proc. ASR-WYP-2005 (JAERI
Hybridization effects and multipole orders in Pr skutterudites
Theoretical account is given of 4f-electron dynamics and multipole orders in
Pr skutterudites with particular attention to (i) mechanism of the crystalline
electric field (CEF) splitting leading to a pseudo-quartet ground state;(ii)
Kondo effect due to exchange interactions involving the pseudo-quartet;(iii)
multipole orders in the lattice of the pseudo-quartet in magnetic
field.Competition between the point-charge interaction andhybridization between
4f and conduction electrons is identified as the key for controlling the CEF
splitting. It is found that one of two pseudo-spins forming the pseudo-quartet
has a ferromagnetic exchange, while the other has an antiferromagnetic exchange
with conduction electrons. The Kondo effect is clearly seen in the resistivity
calculated by the NCA, provided the low-lying triplet above the singlet is
mainly composed of the -type wave functions.If the weight of the
-type is large in the triplet, the Kondo effect does not appear.This
difference caused by the nature of the triplet explains the presence of the
Kondo effect inPrFeP, and its absence in PrOsSb.By taking
the minimal model with antiferro-quadrupole (AFQ) and ferro-type intersite
interactions for dipoles and octupoles between nearest-neighbors,the mean-field
theory reproduces the overall feature of the multiple ordered phases in
PrFeP. The AFQ order with the -type symmetry is found to
be stable only as a mixture of and components.Comment: 21 pages, to be published in proc. YKIS200
Using the N-Alkane Technique to Estimate the Herbage Intake and Diet Composition of Cattle Grazing a \u3cem\u3eMiscanthus Sinensis\u3c/em\u3e Grassland
Plant wax alkanes are now widely used as marker substances (Dove & Mayes 1991) for the estimation of forage intake and diet composition of grazing herbivores. The objective of this study was to evaluate this method with cattle grazing a M. sinensis grassland in Japan
Using the N-Alkane Technique to Estimate the Herbage Intake and Diet Composition of Cattle Grazing a \u3cem\u3eMiscanthus sinensis\u3c/em\u3e Grassland
Plant wax alkanes are now widely used as marker substances (Dove & Mayes 1991) for the estimation of forage intake and diet composition of grazing herbivores. The objective of this study was to evaluate this method with cattle grazing a M. sinensis grassland in Japan
Anomalous time correlation in two-dimensional driven diffusive systems
We study the time correlation function of a density field in two-dimensional
driven diffusive systems within the framework of fluctuating hydrodynamics. It
is found that the time correlation exhibits power-law behavior in an
intermediate time regime in the case that the fluctuation-dissipation relation
is violated and that the power-law exponent depends on the extent of this
violation. We obtain this result by employing a renormalization group method to
treat a logarithmic divergence in time.Comment: 6 page
Electronic Orders Induced by Kondo Effect in Non-Kramers f-Electron Systems
This paper clarifies the microscopic nature of the staggered scalar order,
which is specific to even number of f electrons per site. In such systems,
crystalline electric field (CEF) can make a singlet ground state. As exchange
interaction with conduction electrons increases, the CEF singlet at each site
gives way to Kondo singlets. The collective Kondo singlets are identified with
itinerant states that form energy bands. Near the boundary of itinerant and
localized states, a new type of electronic order appears with staggered Kondo
and CEF singlets. We present a phenomenological three-state model that
qualitatively reproduces the characteristic phase diagram, which have been
obtained numerically with use of the continuous-time quantum Monte Carlo
combined with the dynamical mean-field theory. The scalar order observed in
PrFe_4P_{12} is ascribed to this staggered order accompanying charge density
wave (CDW) of conduction electrons. Accurate photoemission and tunneling
spectroscopy should be able to probe sharp peaks below and above the Fermi
level in the ordered phase.Comment: 7 pages, 8 figure
Mott insulator in two-channel Kondo lattice
The Mott insulator is found in the two-channel Kondo lattice by using the dynamical mean-field theory combined with continuous-time quantum Monte Carlo method. At quarter filling of two conduction bands, the paramagnetic state shows metal-insulator crossover with increasing the coupling constant at low temperatures. The insulating state is explained by the strong coupling limit, where the system is effectively interpreted as the half-filled Hubbard model. It is shown that the present Mott insulating state is well described by the Hubbard I approximation
Microscopic Mechanism for Staggered Scalar Order in PrFe4P12
A microscopic model is proposed for the scalar order in PrFe4P12 where f2
crystalline electric field (CEF) singlet and triplet states interact with two
conduction bands. By combining the dynamical mean-field theory and the
continuous-time quantum Monte Carlo, we obtain an electronic order with
staggered Kondo and CEF singlets with the total conduction number being unity
per site. The ground state becomes semimetallic provided that the two
conduction bands have different occupation numbers. This model naturally
explains experimentally observed properties in the ordered phase of PrFe4P12
such as the scalar order parameter, temperature dependence of the resistivity,
field-induced staggered moment, and inelastic features in neutron scattering.
The Kondo effect plays an essential role for ordering, in strong contrast with
ordinary magnetic orders by the RKKY interaction.Comment: 4 pages, 4figure
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