Dynamics of a fermion in the Kondo-lattice model for strongly correlated systems

Abstract

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 \ensuremath{\Sigma}''(\ensuremath{\omega}>0)\ensuremath{\propto}${\mathrm{\ensuremath{\omega}}}^{\mathrm{\ensuremath{\alpha}}}$, \ensuremath{\alpha}\ensuremath{\le}1, due to the local Kondo-like coupling. Within the perturbation theory we get \ensuremath{\alpha}=1, while the self-consistent treatment yields \ensuremath{\alpha}=1/2. The modified self-consistent equations lead also to better results for the quasiparticle mass.