טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBrisker-Klaiman Daria
SubjectCoherence, Dissipation and Bond Dissociation in Charge
Transport through Molecular Bridges
DepartmentDepartment of Chemistry
Supervisor Professor Uri Peskin
Full Thesis textFull thesis text - English Version


Abstract

Characterizing single molecules in terms of their properties and behavior is a topic of great interest. The study of single molecules is especially challenging since it requires accounting for their quantum mechanical nature as well as their interaction with the surrounding. For example, in a molecular junction scenario, where a molecule is placed between two macroscopic leads, the measured currents reflect not only the electronic properties of the molecule but also the interaction of the molecule with the leads. Moreover, the transmission process usually involves the response of another kind of an environment, the nuclear environment. The nuclear degrees of freedom which are polar or polarizable will respond to the motion of charge through the molecule. This phenomenon which is termed electronic-nuclear coupling is the focus of this dissertation.


In this work the effects of electronic-nuclear coupling was studied in several model systems. First, we considered the scenario of charge transport induced bond dissociation. Two possible mechanisms for dissociation of a chemical bond at the molecular bridge were considered and analyzed using a model of a single anharmonic bridge vibration coupled to an electronic degree of freedom. Next, we studied charge transport mechanisms in DNA molecular junctions, where electronic-nuclear coupling controls the dominant charge transport mechanism, switching between coherent-elastic to incoherent-inelastic transport. In DNA sequences where both charge transport mechanisms are active, the connection strategy between the double-stranded structure to the electrodes was found to act as filter, where the calculated currents through a given connection strategy reflects the contribution of one of the charge transport mechanisms.


Overall, we find that electronic-nuclear coupling can be used as a tool to control and probe the charge transport process through molecular bridges. Our analysis is brought here along suggestions to possible experiments, which I hope will be realized.