ELECTRONIC PROPERTIES OF HEAVILY DOPED TRANS

Stafstrom, S., "Electronic Properties of Heavily Doped Trans-Polyacetylene", p.ll3 in Br6das, J.L. Silbey, R. (Eds.), Conjugated Polymers The Novel Science and technology of Highly Conducting and Nonlinear Optically Active Materials, Kluwer Academic Publishers, Norwell, MA, USA (1991). 

ELECTRONIC PROPERTIES OF HEAVILY DOPED TRANS-POLYACETYLENE... 

Within the continuum model of Takayama, Lin-Liu, and Maki (the TLM model) [27], Dinter [28] has shown that a new type of superlattice exists for tranS (CH). This new type of lattice, which contains considerable dimerization, has a lower total energy than that of the soliton lattice for doping levels above 8%. The electronic band structure corresponding to this lattice configuration contains a partially filled band, i.e., a gapless metallic state exists for this type of lattice. A crossover from the soliton lattice to this new superlattice could therefore explain the onset of metallic properties in heavily doped trans-(CH)y, However, as pointed out by Dinter, calculations using the more realistic discrete SSH model have to be performed in order to check whether or not the new lattice is a mere artifact of the TLM model. 

The metallic properties of the heavily-doped polymers provided the initial focus of interest in the electronic properties, but the theoretical framework for the modelling of the electronic excitations due to Rice [5] and Su et al [6], which for the case of trans-polyacetylene take the form of solitary-wave excitations of the chain, has broadened the area of interest to cover, in particular, the optical and non-linear optical properties of this class of polymos. 

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