Quantum Monte-Carlo calculation of correlation functions of undistorted, cis-distorted and trans-distorted polyacene

We have studied polyacene within the Hubbard model to explore the effect of electrons correlations on the bond–bond correlation as well as spin–spin correlation functions. We employ the determinantal quantum Monte-Carlo to resolve the microscopic Hamiltonian of this system which involves a nearest-neighbor electron hopping matrix element t, an on-site Coulomb repulsion U. The objective of this study is to understand the effect of electron–electron (e–e) correlations on the structural instability in polyacene. We find strong similarities between polyacene and polyacetylene. The system shows no tendency to destroy the imposed bond-alternation pattern. The spin–spin correlations show that undistorted polyacene is susceptible to a spin-density wave distortion for large interaction strength (U).