Numerical renormalization group study of the one-dimensional Kondo insulator.

Abstract

We have studied the one-dimensional Kondo chain at half filling using a density matrix formulation of the numerical renormalization group. The charge gap is larger than the spin gap for all antiferromagnetic values of the exchange coupling.r. A new type of excitation, a neutral spin singlet, consists of a particle and a hole which are repulsive for J≥5t and attractive for J≤5t. As J→0, RKKY interactions become more important and the staggered susceptibility χ(q-2k F ) diverges. We have also studied χ(q) and the dispersion of the low-lying spin excitations as a function of wave vector q