Thermodynamics of doped Kondo insulator in one dimension - Finite-temperature DMRG study

The finite-temperature density-matrix renormalization-group method is appli ed to the one-dimensional Kondo lattice model near half-filling to study it s thermodynamics. The spin and charge susceptibilities and entropy are calc ulated down to T = 0.03t. We find two crossover temperatures near half-fill ing. The higher crossover temperature continuously connects to the spin gap at half-filling, and the susceptibilities are suppressed at around this te mperature. At low temperatures, the susceptibilities increase again with de creasing temperature when doping is finite. We confirm that the susceptibil ities finally approach to the values obtained in the Tomonaga-Luttinger (TL ) liquid ground state for several parameters. The crossover temperature to the TL liquid is a new energy scale determined from gapless excitations of the TL liquid. The transition from the metallic phase to the insulating pha se is accompanied by the vanishing of the lower crossover temperature.