Theoretical Study Of The Charge Transport Through C60 Based Single Molecule Junctions

Author : Leopoldo Meja̕ Restrepo
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (14 download)

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Download or read book Mechanical Control of Charge Transport and Chemical Reactivity in Molecular Junctions written by Leopoldo Meja̕ Restrepo and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Charge transport plays a critical role in a wide range of molecular processes including photosynthesis, redox catalysis, energy storage, biological signaling, and the operation of molecular electronic devices. Understanding and controlling these key events requires establishing how molecular structure influences charge transport and designing physically realizable strategies to manipulate them. This thesis advances the theory, simulation, and interpretation of charge transport experiments in molecular junctions and identifies novel avenues to use external mechanical stimuli to control chemistry and physics in this nanoscale setting. The reason why we focus on molecular junction experiments is because they enable the manipulation of individual molecules and the characterization of their response to external stimuli such as mechanical forces, bias voltages, and electro-magnetic fields. Such a controllable setting is ideal to establish structure-charge transport relations at the single-molecule limit that can inform and resolve the individual molecular contributions to bulk phenomena. We first demonstrate that conductance can act as a sensitive probe of conformational dynamics during the mechanical pulling of molecular junctions. These advances offer an efficient solution to experimentally monitor conformational dynamics at the single-molecule limit. Next, we bridge molecular conductance with mechanochemistry and investigate how to mechanically onset and electrically monitor chemical reactivity in single molecules. In particular, we demonstrate mechanically controlled association and rupture reactions in molecular junctions and show that simultaneous measurements of force and conductance are able to signal reactive events that cannot be distinguished by force or conductance alone. The computations are based on atomistic molecular dynamics and nonequilibrium Green's functions computations of electron transport. At the methodological level, we clarify the utility of the Landauer equation for computing charge transport across molecular junctions immersed in a thermal environment such as solvent. The Landauer equation is central to the modeling of molecular electronics experiments. However, it supposes that the current is coherent (solely due to quantum tunneling) and does not capture the possible influence of the environment in the net current. We isolate physical conditions that require an analysis beyond Landauer and use them to identify chemical motifs capable of stabilizing coherent, incoherent, and intermediate transport mechanisms. Molecular junction experiments typically record the conductance of thousands of freshly formed junctions and report histograms of conductance events. Here, we construct a microscopic theory of such conductance histograms by merging the theory of force spectroscopy developed in biophysics with molecular conductance. The theory enhances the information that can be extracted from molecular electronics experiments, and can be employed to develop schemes to narrow the width of the histograms as desirable for spectroscopic applications and molecular device design. Further, the theory opens key opportunities to atomistically model the conductance histograms, as needed to bridge the gap between theory and experiments."--Pages viii-ix.