Ground-state phase diagram of the one-dimensional t−Js−Jτ model at quarter filling

We study the ground state of the one-dimensional "$t$-$J_s$-$J_{\tau}$ model", which is a variant of the $t$-$J$ model with additional channel degree of freedom. The model is not only a generalization of the $t$-$J$ model but also an effective model of the two-channel Kondo lattice model in the strong coupling region. The low energy excitations and correlation functions are systematically calculated by the density matrix renormalization group (DMRG) method and the ground-state phase diagram at quarter filling consisting of Tomonaga Luttinger liquid, spin-gap state, channel-gap state, insulator, and phase separation is determined. We find that weak channel fluctuations stabilize the spin-gap state, while strong channel fluctuations lead to the transition to the insulator.