Absence of dimer order and the Tomonaga-Luttinger liquid properties of the quarter-filled one-dimensional Kondo-lattice model

A novel spin dimer order is recently reported in the ground state of the one-dimensional Kondo lattice model at quarter-filling. Being dubious about such long-range order in the absence of a spin gap, we perform the density matrix renormalization group calculation at under several boundary conditions. It turns out that dimer spin structure is sensitive to the boundary conditions, and that the dimer correlation function decays in small power law at long distances, indicating the absence of dimer long-range order. This together with a possible absence of charge gap suggests that the true ground state remains to be a Tomonaga-Luttinger liquid with small K_ρ.