96 research outputs found
Perturbative renormalization of multi-channel Kondo-type models
The poor man's scaling is extended to higher order by the use of the
open-shell Rayleigh-Schroedinger perturbation theory. A generalized Kondo-type
model with the SU(n) times SU(m) symmetry is proposed and renormalized to the
third order. It is shown that the model has both local Fermi-liquid and
non-Fermi-liquid fixed points, and that the latter becomes unstable in the
special case of n=m=2. Possible relevance of the model to the newly found phase
IV in Ce_{x}La_{1-x}B_6 is discussed.Comment: 14 pages, 10 Postscript figure
High Temperature Expansion for the SU(n) Heisenberg Model in One Dimension
Thermodynamic properties of the SU() Heisenberg model in one dimension is
studied by means of high-temperature expansion for arbitrary . The specific
heat up to and the correlation function up to are derived with being the antiferromagnetic exchange in
units of temperature. It is found for that the specific heat shows a
shoulder in the high-temperature side of a peak. The origin of this structure
is clarified by deriving the temperature dependence of the correlation
function. With decreasing temperature, the short-range correlation with
two-site periodicity develops first, and then another correlation with -site
periodicity at lower temperature. This behavior is in contrast to that of the
inverse square interaction model, where the specific heat shows a single peak
according to the exact solution. Our algorithm has an advantage that neither
computational time nor memory depends on the multiplicity per site; the
series coefficients are obtained as explicit functions of .Comment: 4 pages including 4 PS-figures, submitted to J. Phys. Soc. Jp
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