Many-body theory of electrical, thermal and optical response of molecular heterojunctions

Persistent Link:
http://hdl.handle.net/10150/194386
Title:
Many-body theory of electrical, thermal and optical response of molecular heterojunctions
Author:
Bergfield, Justin
Issue Date:
2010
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
In this work, we develop a many-body theory of electronic transport through single molecule junctions based on nonequilibrium Green’s functions (NEGFs). The central quantity of this theory is the Coulomb self-energy matrix of the junction ∑(C). ∑(C) is evaluated exactly in the sequential-tunneling limit, and the correction due to finite lead-molecule tunneling is evaluated using a conserving approximation based on diagrammatic perturbation theory on the Keldysh contour. In this way, tunneling processes are included to infinite order, meaning that any approximation utilized is a truncation in the physical processes considered rather than in the order of those processes. Our theory reproduces the key features of both the Coulomb blockade and coherent transport regimes simultaneously in a single unified theory. Nonperturbative effects of intramolecular correlations are included, which are necessary to accurately describe the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap, essential for a quantitative theory of transport. This work covers four major topics related to transport in single-molecule junctions. First, we use our many-body theory to calculate the nonlinear electrical response of the archetypal Au-1,4-benzenedithiol-Au junction and find irregularly shaped ‘molecular diamonds’ which have been experimentally observed in some larger molecules but which are inaccessible to existing theoretical approaches. Next, we extend our theory to include heat transport and develop an exact expression for the heat current in an interacting nanostructure. Using this result, we discover that quantum coherence can strongly enhance the thermoelectric response of a device, a result with a number of technological applications. We then develop the formalism to include multi-orbital lead-molecule contacts and multi-channel leads, both of which strongly affect the observable transport. Lastly, we include a dynamic screening correction to ∑(C) and investigate the optoelectric response of several molecular junctions.
Type:
text; Electronic Dissertation
Keywords:
many-body theory; molecular electronics; optical response; thermoelectrics; transport
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Optical Sciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Stafford, Charles A.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleMany-body theory of electrical, thermal and optical response of molecular heterojunctionsen_US
dc.creatorBergfield, Justinen_US
dc.contributor.authorBergfield, Justinen_US
dc.date.issued2010en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractIn this work, we develop a many-body theory of electronic transport through single molecule junctions based on nonequilibrium Green’s functions (NEGFs). The central quantity of this theory is the Coulomb self-energy matrix of the junction ∑(C). ∑(C) is evaluated exactly in the sequential-tunneling limit, and the correction due to finite lead-molecule tunneling is evaluated using a conserving approximation based on diagrammatic perturbation theory on the Keldysh contour. In this way, tunneling processes are included to infinite order, meaning that any approximation utilized is a truncation in the physical processes considered rather than in the order of those processes. Our theory reproduces the key features of both the Coulomb blockade and coherent transport regimes simultaneously in a single unified theory. Nonperturbative effects of intramolecular correlations are included, which are necessary to accurately describe the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap, essential for a quantitative theory of transport. This work covers four major topics related to transport in single-molecule junctions. First, we use our many-body theory to calculate the nonlinear electrical response of the archetypal Au-1,4-benzenedithiol-Au junction and find irregularly shaped ‘molecular diamonds’ which have been experimentally observed in some larger molecules but which are inaccessible to existing theoretical approaches. Next, we extend our theory to include heat transport and develop an exact expression for the heat current in an interacting nanostructure. Using this result, we discover that quantum coherence can strongly enhance the thermoelectric response of a device, a result with a number of technological applications. We then develop the formalism to include multi-orbital lead-molecule contacts and multi-channel leads, both of which strongly affect the observable transport. Lastly, we include a dynamic screening correction to ∑(C) and investigate the optoelectric response of several molecular junctions.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectmany-body theoryen_US
dc.subjectmolecular electronicsen_US
dc.subjectoptical responseen_US
dc.subjectthermoelectricsen_US
dc.subjecttransporten_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineOptical Sciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairStafford, Charles A.en_US
dc.contributor.committeememberStafford, Charles A.en_US
dc.contributor.committeememberJacquod, Philippeen_US
dc.contributor.committeememberMazumdar, Sumitendraen_US
dc.identifier.proquest11306en_US
dc.identifier.oclc752261152en_US
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