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2 Materials Science Poland

2 2007

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

Walczak K.

Materials Science Poland

2007

Vol. 25, No. 2

519--525

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.

Polaronic transport through DNA molecules

Sidowski M., Walczak K.

Materials Science Poland

2007

Vol. 25, No. 2

577--582

We present results of theoretical studies on polaronic and incoherent transport through a DNA-based junction. Decoherence itself is modelled through the use of an imaginary dephasing potential. Nonperturbative computational scheme, used in this work, is based on Green's functions within the framework of the so-called polaron transformation (GFT-PT). This method maps exactly the many-body hole -phonon interaction problem into a one-body multi-channel scattering problem, where the availability of particular conduction channels is determined by an appropriate weight factor. The results obtained for poly(dG)-poly(dC) DNA molecule reveal saturation effect of the current at high voltages, where for short chains we establish an exponential DNA length dependence. Besides, we document strong coupling and exponential dephasing dependences of the maximum current.