Polaronic transport through molecular quantum dots. Charging-induced NDR and rectification

The polaronic transport through molecules weakly connected to metallic electrodes in the nonlinear response regime has been studied. Molecule itself is treated as a quantum dot with discrete energy levels, its connection to the electrodes is described within the wide-band approximation, while the charging is incorporated by means of the self-consistent potential. Non-perturbative computational scheme, used in this work, is based on the Green's function theory within the framework of polaron transformation. This method transforms the many-body electron-phonon interaction problem into a one-body multi-channel single-electron scattering problem with occupation of polaron levels calculated in a self-consistent way. In particular, three different phenomena are discussed in detail resulting from charging in polaronic transport via discrete quantum states: the suppression of the current at higher voltages, negative differential resistance (NDR effect), and rectification.