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postgraduate thesis: Quantum transport theory for AC response and its combination with electromagnetic method

TitleQuantum transport theory for AC response and its combination with electromagnetic method
Authors
Issue Date2014
PublisherThe University of Hong Kong (Pokfulam, Hong Kong)
Citation
Yin, Z. [殷振宇]. (2014). Quantum transport theory for AC response and its combination with electromagnetic method. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5387998
AbstractThe time-dependent quantum transport theory has attracted a great deal of interest in the past decade. However, some concepts in the frequency-dependent transport theory remain confused. Based on the Keldysh non-equilibrium green’s function formalism for time-dependent quantum transport, new expressions for dynamic current and admittance are derived in this thesis, which satisfy gauge invariance and current continuity. The key concepts in this field are clarified. The derivation is under wideband limit (WBL) and first order approximations. This new formalism is validated by first-principle time-dependent calculations of three carbon-based nano-devices. Later a study on asymmetric systems is carried out by this new theory, and discussion on current conversation problem is presented. This new ac quantum transport theory can cooperate with electromagnetic method to solve a mesoscopic problem. The active core part which is usually under atomistic scale is simulated by frequency-domain quantum transport theory, while the broad environment is tackled with electromagnetic solver. By a careful treatment at the interface between two solvers, this quantum mechanic / electromagnetic (QM/EM) method is implemented self-consistently. This QM/EM method is also validated by calculations of the transient current through a carbon-nanotube based device surrounded by silicon environment under a small ac bias voltage. The small signal and WBL approximations are also adopted in the development of this method. As a supplementary to the family of QM/EM methods (static and time-dependent QM/EM method are already established), this method shows very good efficient and high accuracy. Beyond linear response in frequency domain, we have also studied some nonlinear effects. As one application of nonlinear effect, memristor has attracted great attention in the past few years. Through Fourier analysis method, we have now understood the physical and mathematical mechanisms of ideal memristor, memcapacitor and meminductor. We have proposed methods to verify ideal memristor, memcapacitor and memdicutor, and to find out their intrinsic parameters which can be employed to predict their behavior under various input signals. This study may also provide an instruction on experimental research.
DegreeDoctor of Philosophy
SubjectQuantum theory
Transport theory
Dept/ProgramChemistry
Persistent Identifierhttp://hdl.handle.net/10722/208616

 

DC FieldValueLanguage
dc.contributor.authorYin, Zhenyu-
dc.contributor.author殷振宇-
dc.date.accessioned2015-03-13T01:44:09Z-
dc.date.available2015-03-13T01:44:09Z-
dc.date.issued2014-
dc.identifier.citationYin, Z. [殷振宇]. (2014). Quantum transport theory for AC response and its combination with electromagnetic method. (Thesis). University of Hong Kong, Pokfulam, Hong Kong SAR. Retrieved from http://dx.doi.org/10.5353/th_b5387998-
dc.identifier.urihttp://hdl.handle.net/10722/208616-
dc.description.abstractThe time-dependent quantum transport theory has attracted a great deal of interest in the past decade. However, some concepts in the frequency-dependent transport theory remain confused. Based on the Keldysh non-equilibrium green’s function formalism for time-dependent quantum transport, new expressions for dynamic current and admittance are derived in this thesis, which satisfy gauge invariance and current continuity. The key concepts in this field are clarified. The derivation is under wideband limit (WBL) and first order approximations. This new formalism is validated by first-principle time-dependent calculations of three carbon-based nano-devices. Later a study on asymmetric systems is carried out by this new theory, and discussion on current conversation problem is presented. This new ac quantum transport theory can cooperate with electromagnetic method to solve a mesoscopic problem. The active core part which is usually under atomistic scale is simulated by frequency-domain quantum transport theory, while the broad environment is tackled with electromagnetic solver. By a careful treatment at the interface between two solvers, this quantum mechanic / electromagnetic (QM/EM) method is implemented self-consistently. This QM/EM method is also validated by calculations of the transient current through a carbon-nanotube based device surrounded by silicon environment under a small ac bias voltage. The small signal and WBL approximations are also adopted in the development of this method. As a supplementary to the family of QM/EM methods (static and time-dependent QM/EM method are already established), this method shows very good efficient and high accuracy. Beyond linear response in frequency domain, we have also studied some nonlinear effects. As one application of nonlinear effect, memristor has attracted great attention in the past few years. Through Fourier analysis method, we have now understood the physical and mathematical mechanisms of ideal memristor, memcapacitor and meminductor. We have proposed methods to verify ideal memristor, memcapacitor and memdicutor, and to find out their intrinsic parameters which can be employed to predict their behavior under various input signals. This study may also provide an instruction on experimental research.-
dc.languageeng-
dc.publisherThe University of Hong Kong (Pokfulam, Hong Kong)-
dc.relation.ispartofHKU Theses Online (HKUTO)-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rightsThe author retains all proprietary rights, (such as patent rights) and the right to use in future works.-
dc.subject.lcshQuantum theory-
dc.subject.lcshTransport theory-
dc.titleQuantum transport theory for AC response and its combination with electromagnetic method-
dc.typePG_Thesis-
dc.identifier.hkulb5387998-
dc.description.thesisnameDoctor of Philosophy-
dc.description.thesislevelDoctoral-
dc.description.thesisdisciplineChemistry-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.5353/th_b5387998-

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