ELECTRONIC STATES IN DOPED TRANS-POLYACETYLENE - COHERENT POTENTIAL APPROXIMATION AND COMPENSATED DOPING

Disorder effects in doped trans-polyacetylene are studied, using an extended Takayama—Lin-Liu—Maki (TLM) model. Bond- and site-type impurity models are analyzed when the doping is compensated. Electronic states are calculated by the self-consistent Born approximation (SCBA) and also by the coherent potential approximation (CPA). Results do not depend on the type of the impurity. We find that peaks in the electronic density of states become steeper and the energy gap is wider in the CPA than in the SCBA, while change in the order parameter is small. Two critical concentrations, where the gap and the order parameter vanish, come close each other. A phase diagram is given for the electronic structures in the CPA. For the site-type impurities, two impurity bands are found in association with the two signs of impurities. For the bond-type impurities, the total energy recovers the symmetry property for the order parameter. © 1990, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.