Large Fermi surface of the one-dimensional Kondo lattice model observed by Friedel oscillations

The paramagnetic metallic phase of the one-dimensional Kondo lattice model is studied by the density matrix renormalization group method. We calculate spin excitation gap and Friedel oscillations in finite systems. The finite size corrections of the spin gap and the long-range Friedel oscillations are consistent with a Tomonaga-Luttinger liquid. The Friedel oscillations reflect the charge-charge and spin-spin correlation functions. From the period of the Friedel oscillations, it is concluded that the Fermi surface is large including both the conduction electrons and the localized spins, k_F = π(1+n_c)/2 where n_c is the density of conduction electrons.