Particle path correlations in a phonon bath

The path integral formalism is applied to derive the full partition function of a generalized Su–Schrieffer–Heeger Hamiltonian describing particle motion in a bath of oscillators. The electronic correlations are computed versus temperature for some choices of oscillator energies. We study the perturbing effect of a time-averaged particle path on the phonon subsystem, deriving the relevant temperature-dependent cumulant corrections to the harmonic partition function and free energy. The method has been applied to compute the total heat capacity up to room temperature: a low temperature upturn in the heat capacity over temperature ratio points to a glassy-like behaviour ascribable to a time-dependent electronic hopping with variable range in the linear chain.