The influence of vibronic coupling on the shape of transport characteristics in inelastic tunneling through molecules

Abstract

Here we present theoretical studies of the effect of vibronic coupling on nonlinear transport characteristics (current-voltage and conductance-voltage) in molecular electronic devices. Considered device is composed of molecular quantum dot (with discrete energy levels) weakly connected to metallic electrodes (treated within the wide-band approximation), where molecular vibrations are modeled as dispersionless phonon excitations. Nonperturbative computational scheme, used in this work, is based on the Green's function theory within the framework of mapping technique (GFT-MT) which transforms the many-body electron-phonon interaction problem into a one-body multi-channel single-electron scattering problem. In particular, it is shown that quantum coherent transport of virtual polarons through the molecule can be a dominant factor justifying some well-known discrepancies between theoretical calculations and experimental results.

Tracing electronic pathways in molecules by using inelastic tunneling spectroscopy

“…1), the only added experimental requirement is the ability to cool the junction. From comparison between experiments and computations (10)(11)(12)(13)(14)(15)(16)(17), IETS is useful for characterizing numerous aspects of molecular junctions such as the actual presence of the molecule, information on the nature of the interfaces (18), the orientation of the molecule (19), and some symmetry aspects of the junction (20, 21).…”

Spin-dependent shot noise of inelastic transport through molecular quantum dots

“…In this way, the many-body electron-phonon interaction problem is mapped into a multi-channel single-electron scattering problem [27,[34][35][36][37][38][39][40].…”

Decoherence in elastic and polaronic transport via discrete quantum states

“…1 and discussed elsewhere [20][21][22][23][24][25][26][27][28][29]. After eliminating the degrees of freedom of the two electrodes and the dephasing reservoir, we can present the effective Hamiltonian of the reduced molecular system in the form…”

“…The IETS spectra are also very sensitive to the device working temperature and intramolecular conformational changes. So far, inelastic transport was treated as a purely coherent transfer process [20][21][22][23][24][25][26][27][28][29]. However, coherent tunneling cannot get very far at room temperatures, since thermal disorder destroys the orbital delocalization leading to incoherent transport [30][31][32][33] and some of the experimental data may be interpreted in this sense [34][35][36][37][38][39].…”

“…The calculations are performed using a nonperturbative computational scheme, based on Green's function theory within the framework of polaron transformation (GFT-PT). This method transforms the many-body electron-phonon interaction problem into a singleelectron many-channel scattering problem [20][21][22][23][24][25][26][27][28][29]. Here we analyze the electrical current and shot noise (current fluctuations of purely quantum origin) in two response regimes: linear and nonlinear, respectively.…”