Commuting quantum transfer-matrix approach to intrinsic fermion system: Correlation length of a spinless fermion model

The quantum transfer-matrix approach to integrable lattice fermion systems is presented. As a simple case we treat the spinless fermion model with rep ulsive interaction in critical regime. We derive a set of nonlinear integra l equations which characterize the free energy and the correlation length o f (c (dagger)(j) c(i)) for an arbitrary particle density at any finite temp eratures. The correlation length is determined by solving the integral equa tions numerically. Especially in the low-temperature limit this result agre es with the prediction from conformal field theory with high accuracy. [S01 63-1829(99)13827-X].