Coherent and dissipative dc transport in quasi-one-dimensional systems of coupled polyaniline chains

We present numerical studies on the conductance of coupled polyaniline chains. Our investigation is based on a tight-binding Hamiltonian, which comprises the description of the single polymer chains as well as interchain interactions. Phase-breaking processes are included in the Hamiltonian via imaginary self-energy corrections within the Green's-function formalism describing the system. The variation of these self-energies allows one to describe the transport over the full range in between the coherent and dissipative regimes. In the coherent limit we observe a transition from exponential to power-law localization upon increasing the size of the cross section of the quasi-one-dimensional systems. This behavior is all the more pronounced, the smaller the disorder in the specimen is. Upon introducing dissipation into the system we can identify metallic, insulating, and critical samples of polyaniline. These observations are consistent with recent experimental results, which characterize polyaniline-camphor sulfonic acid as a system at the metal-insulator transition.