טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentMichael Iv
SubjectManifestation of Quantum Mechanical Unfurling in Transport
through Single Molecule Junctions
DepartmentDepartment of Chemistry
Supervisor Full Professor Peskin Uri
Full Thesis textFull thesis text - English Version


Abstract

A new thermally activated charge transport mechanism, coined as Quantum Mechanical Unfurling, was recently proposed in order to explain distance-independent charge transport rates in highly ordered poly-Adenine DNA sequences. In this work the manifestation of this mechanism is examined in a molecular junction setup, where the molecular charge transfer process is coupled to a thermal environment and to electrodes. A minimal model approach was applied in order to capture the dynamics of hole transport through a single poly-A DNA molecule, modeled as a Donor-Bridge-Acceptor (DBA) system. A kinetic scheme for the charge transport and energy distribution inside the molecule under a bias potential has been developed and analyzed.

The model calculations suggest a new manifestation of Quantum Mechanical Unfurling in single molecule junctions, where the current increases with the length of the molecular bridge. Such unusual behavior was recently observed experimentally in the (coherent) ballistic transport regime, and was attributed to delocalization of charges inside an ordered molecular bridge. Here, it predicted to be observed for thermally activated (incoherent) transport through ordered molecular bridges. Several predications are proposed, regarding the influence of the thermal environment and the physical parameters of the leads.

Our analysis of the non-equilibrium steady state currents reveals the presence of subspaces in the molecular Fock space, associated with groups of quasi-thermalized states. The existence of these “Boltzmannized sub-spaces” can be utilized in new algorithms that overcome the exponential growth of the computational effort in simulations of transport through molecular bridge with increasing lengths.