K. Lehur, HOLE DOPING AND DISORDER EFFECTS ON THE ONE-DIMENSIONAL KONDO-LATTICE, FOR FERROMAGNETIC KONDO COUPLINGS, Physical review. B, Condensed matter, 56(21), 1997, pp. 14058-14065
We investigate the one-dimensional Kondo lattice model for ferromagnet
ic Kondo couplings. The so-called ferromagnetic two-leg spin ladder an
d the S=1 antiferromagnet occur as one-dimensional Kondo insulators. B
oth exhibit a spin gap. But, in contrast to the strong-coupling limit,
the Haldane state which characterizes the two-leg spin-ladder Kondo i
nsulator cannot fight against very weak exterior perturbations. First,
by using standard bosonization techniques, we prove that an antiferro
magnetic ground state occurs by doping with few holes; it is character
ized by a form factor of the spin-spin correlation functions which exh
ibits two structures, respectively, at q=pi and q=2k(F). Second, we pr
ove precisely by using renormalization-group methods that the Anderson
localization inevitably takes place in that weak-coupling Haldane sys
tem, by the introduction of quenched randomness; the spin-fixed point
rather corresponds to a ''glass'' state, Finally, a weak-coupling anal
og of the S=1 antiferromagnet Kondo insulator is proposed; we show tha
t the transition into the Anderson-localization state maybe avoided in
that unusual weak-coupling Haldane system.