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

The finite-temperature density-matrix renormalization-group method is applied to the one-dimensional Kondo lattice model near half-filling to study its thermodynamics. The spin and charge susceptibilities and entropy are calculated down to T = 0.03t. We find two crossover temperatures near half-filling. The higher crossover temperature continuously connects to the spin gap at half-filling, and the susceptibilities are suppressed at around this temperature. At low temperatures, the susceptibilities increase again with decreasing temperature when doping is finite. We confirm that the susceptibilities 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 phase is accompanied by the vanishing of the lower crossover temperature.