DYNAMICS OF A FERMION IN THE KONDO-LATTICE MODEL FOR STRONGLY CORRELATED SYSTEMS

The motion of a single fermion coupled to the planar antiferromagnetic spin background is examined within the Kondo-lattice model, including the local spin-fermion coupling and the spin-dependent hopping. The perturbation theory using lowest-order magnon processes and the self-consistent calculation of the quasiparticle spectra, yields several features obtained by an analogous treatment of the t-J model by Kane et al. Qualitative differences are, however, found in low excited states with the self-energy showing a nonanalytical behavior (>0)±, ±1, due to the local Kondo-like coupling. Within the perturbation theory we get ±=1, while the self-consistent treatment yields ±=1/2. The modified self-consistent equations lead also to better results for the quasiparticle mass. © 1990 The American Physical Society.