Theory and simulation of vibrationally inelastic electron transport through molecular bridges

Prof. Dr. Wolfgang Domke and PD Dr. Michael Thoss, Technische Universität München

The aim of the project is to obtain a comprehensive understanding of the influence of the vibrational degrees of freedom of the molecular bridge on electron transport through molecular junctions. To this end, we plan to develop the appropriate theoretical methodology to describe vibrationally inelastic electron transport through molecular bridges and apply these methods to selected systems. The former part of the project involves the extension of the methods used in our previous work in three directions: (i) quantum chemical determination of the relevant molecular parameters in the vibronic Hamiltonian under finite bias voltage, employing NEGF-DFT calculations for fixed nuclei, (ii) incorporation of vibrational non-equilibrium effects in transport calculations based on kinetic rate equations as well as NEFG theory beyond the self-consistent Born approximation, (iii) ab initio treatment of electron-correlation effects in molecular bridges. Based on this methodology, we plan to simulate current-voltage characteristics for selected representative systems including benzene and thiophene oligomers connected via alkanethiol bridges to gold electrodes. In addition, we plan to study several  processes/mechanisms which are of importance for a detailed understanding of conductance in molecular junctions, in particular, current induced heating and  the possible breakage of the molecular bridge, vibronic coupling  phenomena in molecules with degenerate electronic states, as well as effects of large-amplitude anharmonic motion.