Non-equilibrium Charge Transport in a Conjugated Polymer.

To address the non-equilibrium transport mechanism in a conjugated polymer, we investigate the dynamics of the lattice deformation and the charge transport in a polymer chain coupled with the reservoirs by the time-dependent non-equilibrium Green's function (TDNEGF) formulism. We find that the delocalized soliton lattice wave (SLW) forms in the polymer, rather than the well-known localized excitations such as polarons and solitons. The source reservoir drives an electron-like transient dynamic SLW while the drain reservoir drives the hole-like one. These transient SLWs propagate in opposite directions and then merge and relax to a steady SLW. These results are confirmed by our analytical derivation based on the continuum model. When the bias voltages are symmetric (μL=-μR), the dynamic SLW subsides to the stationary soliton lattice (SL). In the energy domain, the sandwich-structured non-full filled SL bands form in the original gap, which can provide the conduction channels. Especially, in the case of the symmetric bias voltages (μL=-μR), the SL band is half-filled. The transmission current is the major part of the total current and the rest minor part is the effective current induced by the charge density waves accompanied by the SLW.