63 research outputs found
Wilson and Kadowaki-Woods Ratios in Heavy Fermions
Recently we have shown that a one-parameter scaling, , describes the
physical behavior of several heavy fermions in a region of their phase diagram.
In this paper we fully characterize this region, obtaining the uniform
susceptibility, the resistivity and the specific heat in terms of the coherence
temperature . This allows for an explicit evaluation of the Wilson and
the Kadowaki-Woods ratios in this regime. These quantities turn out to be
independent of the distance to the quantum critical point (QCP). The
theory of the one-parameter scaling corresponds to a local interacting model.
Although spatial correlations are irrelevant in this case, time fluctuations
are critically correlated as a consequence of the quantum character of the
transition.Comment: 6 pages, 1 figure, to be published in Eur.Phys.J.
Dimensional Crossover in Heavy Fermions
Recently we have shown that a one-parameter scaling, the Coherence
Temperature, describes the physical behavior of several heavy fermions in a
region of their phase diagram. In this paper we fully characterize this region,
obtaining the uniform susceptibility, the resistivity and the specific heat.
This allows for an explicit evaluation of the Wilson and the Kadowaki-Woods
ratios in this regime. These quantities turn out to be independent of the
distance to the critical point. The theory of the one-parameter scaling
corresponds to a zero dimensional approach. Although spatial correlations are
irrelevant in this case, time fluctuations are critically correlated and the
quantum hyperscaling relation is satisfied for . The crossover from
to is smooth. It occurs at a lenght scale which is inversely related to
the stiffness of the lifetime of the spin fluctuations.Comment: 4 pages, revtex, no figures, submitted to Physical Review
Thermodynamic quantum critical behavior of the Kondo necklace model
We obtain the phase diagram and thermodynamic behavior of the Kondo necklace
model for arbitrary dimensions using a representation for the localized and
conduction electrons in terms of local Kondo singlet and triplet operators. A
decoupling scheme on the double time Green's functions yields the dispersion
relation for the excitations of the system. We show that in there is
an antiferromagnetically ordered state at finite temperatures terminating at a
quantum critical point (QCP). In 2-d, long range magnetic order occurs only at
T=0. The line of Neel transitions for varies with the distance to the
quantum critical point QCP as, where the shift
exponent . In the paramagnetic side of the phase diagram, the
spin gap behaves as for consistent with
the value found for the dynamical critical exponent. We also find in this
region a power law temperature dependence in the specific heat for
and along the non-Fermi liquid trajectory. For , in the so-called Kondo spin liquid phase, the thermodynamic
behavior is dominated by an exponential temperature dependence.Comment: Submitted to PR
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