Single-particle excitations of the Kondo lattice

We present a simple theory for the description of the single-particle excitations of the Kondo lattice model. We derive an effective Hamiltonian that describes the coherent propagation of single-particle-like fluctuations on a strong-coupling ground state. Even for f electrons that are replaced by Kondo spins, the resulting spectral function obeys the Luttinger theorem including the f electrons, and our calculation reproduces the complicated evolution of the spectral function with electron density seen in numerical studies.