EFFECTS OF ELECTRON CORRELATION ON DOPING IN CONJUGATED POLYMERS - A STUDY OF THE SSHH AND BKH MODELS USING THE DMRG METHOD

We adopt the Su-Schrieffer-Heeger (SSH) Hamiltonian supplemented by a Hubbard term, which we call the SSHH model, for systems with a degener ate ground state, and the Brazovskii-Kirova (BK) Hamiltonian supplemen ted by a Hubbard term (BKH model) for systems with a nondegenerate gro und state, to study the effect of electron correlation on doping in co njugated polymers. The density matrix renormalization group (DMRG) tec hnique developed by White has proved to be a very powerful tool for tr eating low-dimensional systems with strong correlation. This method is applied to the above models. We first study the metal-insulator trans ition within the SSHH model. With the BKH model, we investigate the fo rmation of bipolarons versus separated polarons in a nondegenerate sys tem. Optical signatures of polarons are also calculated.