Download or read book Many body Effects on the Quasiparticle and Optical Properties of Quasi two dimensional Systems written by Diana Y. Qiu and published by . This book was released on 2017 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt: Quasi-two-dimensional (quasi-2D) semiconductors are the subject of intense research interest as platforms for both developing atomically-thin devices and exploring novel physics. These are atomically-thin structured derived from layered materials with covalent bonding in each layer and weak coupling between layers so that individual monolayers can be easily peeled off. Changes in confinement and screening in reduced dimensions can lead to drastic changes in quasiparticle (QP) and optical properties when compared with bulk materials. In this dissertation, we use ab initio methods based on many-body perturbation theory (MBPT) to explain and predict the QP and optical properties of quasi-2D semiconductors. We describe the QP properties within the GW approximation, for single particle excitations, and the optical properties within the GW plus Bethe Salpeter equation (GW-BSE) approach, for two particle excitations, such as correlated electron-hole pairs, or excitons. We find that, in general, reduced dimensionality results in strong spatial variations in the screening of the Coulomb interaction as well as reduced total screening, allowing for strongly-bound, non-hydrogenic excitons. We then use this understanding to explore how changing the external screening environment through layering and substrate engineering can be used to tune properties of quasi-2D materials. Finally, we perform ab initio calculations of exciton dispersion in quasi-2D and show that the 2D Coulomb interaction can give rise to unusual, massless excitons. This dissertation is organized as follows: In chapter 1, we introduce the theoretical and computational techniques used to compute the QP and optical properties of real materials. In chapter 2, we calculate the QP bandstructure and optical spectrum of monolayer MoS2, a prototypical quasi-2D semiconductor. We find that monolayer MoS2 has very strongly-bound excitons, with binding energies that are two orders of magnitude larger than in the bulk. Moreover, we show that these excitons have excited states that do not follow the commonly used 2D hydrogenic model and that this strongly-bound, non-hydrogenic behavior arises as a consequence of fast spatial variations in the screening environment. For isolated systems, the screening is in fact diminished to zero in the limit of large distances compared to the layer thickness. The inhomogeneous screening found in quasi-low-dimensional systems introduces significant computational challenges because very fine spatial sampling is required to capture this variation in screening. In chapter 3, we develop new computational techniques to sample reciprocal space more efficiently, resulting in more than two orders of magnitude reductions in computational time for GW and GW-BSE calculations on low-dimensional systems. Based on our understanding of screening in MoS2, we then explore how screening from a substrate or capping layer might change the electronic and optical properties in other quasi-2D materials. In a joint experimental study, we find that a bilayer graphene substrate can renormalize the QP band gap and exciton binding energies in monolayer and few-layer transition metal dichalcogenides (TMDs) by as much as 30%. This work is discussed in chapters 4 and 5. In chapter 6, we discuss how the substrate screening effect is even more pronounced in black phosphorene, which has a lower intrinsic screening than TMDs. Consequently, encapsulation, which is commonly used to stabilize the material under ambient conditions, can completely eliminate the presence of bound excitons in few-layer systems, changing the optical spectrum qualitatively as well as quantitatively. Traditional implementations of the GW-BSE approach focus on excitons with zero center-of-mass momentum (Q), since these are the states probed by linear optical probes. However, exciton dispersion--energy as a function of Q--is essential to understanding properties such as exciton dynamics, lifetimes, and the formation of novel phases such as exciton condensates. In chapter 7, we implement GW-BSE for finite Q, and calculate the exciton bandstructure of MoS2. We find that, in general, the exchange interaction in 2D gives rise to a massless dispersion, while in MoS2 and other TMDs in particular, the interplay of the intervalley and intravalley exchange gives rise to a parabolic band and a massless, v-shaped band with a valley quantum phase of winding number two.

Download or read book Quasiparticle and Optical Properties of Quasi two dimensional Systems written by Felipe Homrich da Jornada and published by . This book was released on 2017 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since the experimental isolation of graphene in 2004, there has been tremendous interest in studying quasi-two-dimensional (quasi-2D) systems. These atomically thin materials display a number of unique properties not found in their bulk counterparts, such as large self-energy and excitonic effects due to weaker screening in 2D. However, simple dimensionality arguments alone often fail to give quantitative - and sometimes qualitative - explanation of physical phenomena in these systems. Many low-energy excitation processes in these materials involve length scales comparable to the extent of these materials along the confined direction. Thus, many of these interesting properties are a result of the interplay of the physics of 2 and 3 dimensions. In order to predict quasiparticle and optical properties in these materials, it is therefore highly important to use methods that capture the explicit quasi-2D crystal structure and rely on as little experimental input as possible. Ab initio formalisms are well-tested, mature, and predictive methods for calculating physical properties of systems with arbitrary crystal structure and dimensionality. In particular, the ab initio GW and GW plus Bethe-Salpeter equation (BSE) approaches are reliable methods to compute quasiparticle and optical properties of materials without experimental parameters and for systems with arbitrary electronic structure and dimensionality. In this dissertation, we study the quasiparticle and optical properties of quasi-2D systems, with emphasis on graphene and monolayer transition metal dichalcogenides. This dissertation is divided into three parts. In the first part, we introduce the formalisms that allow us to compute quasiparticle and optical properties of material. We include a brief review of the quasiparticle approximation, and connect it to Green's function methods. We then introduce the GW approximation and the BSE as tools to compute quasiparticle and optical properties of materials, respectively. We include a simplified derivation of these two formalisms in terms of many-body perturbation theory and diagrammatic series. We also review how the GW approximation and the BSE are implemented into ab initio electronic-structure codes, such as BerkeleyGW. In the second part of the dissertation, we show our theoretical works on the quasiparticle and optical properties of quasi-2D systems. We compute the quasiparticle bandstructure, optical absorption spectrum, and excitonic series on monolayer MoS2, a prototypical quasi-2D semiconductor. We also understand the origin of novel physics in these materials, such as the presence of excitonic states that cannot be understood in terms of a 2D hydrogenic model. We understand these unique phenomena in terms of the unique features of the screening in 2D, and also show how this leads to severe challenges in applying the GW and GW-BSE approaches to system with reduced dimensionality. We then develop new methods that efficiently capture these fast variations of the screening, and reduce the computational cost of GW and GW-BSE approaches on these systems by orders of magnitude. Finally, in the third part of the dissertation, we show a variety of projects that are collabo- rations between our theoretical group at Berkeley and various experimental groups. In the first collaboration, we perform a joint work with Prof. Tony Heinz’s experimental group, wherein we demonstrate how excitonic effects on graphene can be tuned by carrier doping. Our work goes beyond the independent-particle picture, and includes, without adjustable parameters, the effect of finite quasiparticle lifetimes due to electron-electron and electron-phonon interactions on the optical absorption of graphene. The second project in this part - a collaboration with the experimental groups of Profs. Mike Crommie and Feng Wang - directly measures the exciton binding energy in MoSe2. Because these measurements are performed on a substrate of bilayer graphene, we develop a new method to include the effect of screening from the substrate into our ab initio formalism. Finally, the third joint theory-experiment work was a collaboration with Prof. Mike Crommie’s group, wherein we compute the quasiparticle properties of few-layer MoSe2 and simulate the corresponding scanning-tunneling spectroscopy curves. Our work shows how the electronic structure of MoSe2 evolves with layer number, and elucidates the role of layer hybridization, self-energy effects, and intrinsic/extrinsic screening in the quasiparticle properties of few-layer transition metal dichalcogenides.

Download or read book Rich Quasiparticle Properties of Low Dimensional Systems written by Dr Cheng-Hsueh Yang and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses the essential properties of carbon nanotubes and 2D graphene systems. The book focuses on the fundamental excitation properties of a large range of graphene-related materials, presenting a new theoretical framework that couples electronic properties and e-e Coulomb interactions together in order to thoroughly explore Coulomb excitations and decay rates in carbon-nanotube-related systems.

Download or read book Rich Quasiparticle Properties In Layered Graphene related Systems written by Ming-fa Lin and published by World Scientific. This book was released on 2023-12-27 with total page 445 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive book delves into the fascinating world of quasiparticle properties of graphene-related materials. The authors thoroughly explore the intricate effects of intrinsic and extrinsic interactions on the material's properties, while unifying the single-particle and many-particle properties through the development of a theoretical framework. The book covers a wide range of research topics, including long-range Coulomb interactions, dynamic charge density waves, Friedel oscillations and plasmon excitations, as well as optical reflection and transmission spectra of thin films. Also it highlights the crucial roles of inelastic Coulomb scattering and optical scattering in the quasiparticle properties of layered systems, and the impact of crystal symmetry, number of layers, and stacking configuration on their uniqueness. Furthermore, the authors explore the topological properties of quasiparticles, including 2D time-reversal-symmetry protected topological insulators with quantum spin Hall effect, and rhombohedral graphite with Dirac nodal lines. Meanwhile, the book examines the gate potential application for creating topological localized states and shows topological invariants of 2D Dirac fermions, and binary Z2 topological invariants under chiral symmetry. The calculated results are consistent with the present experimental observations, establishing it as a valuable resource for individuals interested in the quasiparticle properties of novel materials.

Download or read book Handbook of Thin Films Five Volume Set written by Hari Singh Nalwa and published by Academic Press. This book was released on 2001-10-29 with total page 661 pages. Available in PDF, EPUB and Kindle. Book excerpt: This five-volume handbook focuses on processing techniques, characterization methods, and physical properties of thin films (thin layers of insulating, conducting, or semiconductor material). The editor has composed five separate, thematic volumes on thin films of metals, semimetals, glasses, ceramics, alloys, organics, diamonds, graphites, porous materials, noncrystalline solids, supramolecules, polymers, copolymers, biopolymers, composites, blends, activated carbons, intermetallics, chalcogenides, dyes, pigments, nanostructured materials, biomaterials, inorganic/polymer composites, organoceramics, metallocenes, disordered systems, liquid crystals, quasicrystals, and layered structures. Thin films is a field of the utmost importance in today's materials science, electrical engineering and applied solid state physics; with both research and industrial applications in microelectronics, computer manufacturing, and physical devices. Advanced, high-performance computers, high-definition TV, digital camcorders, sensitive broadband imaging systems, flat-panel displays, robotic systems, and medical electronics and diagnostics are but a few examples of miniaturized device technologies that depend the utilization of thin film materials. The Handbook of Thin Films Materials is a comprehensive reference focusing on processing techniques, characterization methods, and physical properties of these thin film materials.

Download or read book Binding and Scattering in Two Dimensional Systems written by J. Timothy Londergan and published by Springer Science & Business Media. This book was released on 1999-11-17 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph is accessible to anyone with an undergraduate background in quantum mechanics, electromagnetism and some solid state physics. It describes in detail the properties of particles and fields in quasi-two-dimensional systems used to approximate realistic quantum heterostructures. Here the authors treat wires, i.e. they assume an infinite hard-wall potential for the system. They discuss bound states, the properties of transmission and reflection, conductance, etc. It is shown that the simple models developed in this book in detail are capable of understanding even complex physical phenomena. The methods are applied to optical states in photonic crystals, and similarities and differences between those and electronic states in quantum heterostructures and electromagnetic fields in waveguides are discussed.

Download or read book Handbook of Thin Films Five Volume Set written by Hari Singh Nalwa and published by Elsevier. This book was released on 2001-11-17 with total page 3451 pages. Available in PDF, EPUB and Kindle. Book excerpt: This five-volume handbook focuses on processing techniques, characterization methods, and physical properties of thin films (thin layers of insulating, conducting, or semiconductor material). The editor has composed five separate, thematic volumes on thin films of metals, semimetals, glasses, ceramics, alloys, organics, diamonds, graphites, porous materials, noncrystalline solids, supramolecules, polymers, copolymers, biopolymers, composites, blends, activated carbons, intermetallics, chalcogenides, dyes, pigments, nanostructured materials, biomaterials, inorganic/polymer composites, organoceramics, metallocenes, disordered systems, liquid crystals, quasicrystals, and layered structures. Thin films is a field of the utmost importance in today's materials science, electrical engineering and applied solid state physics; with both research and industrial applications in microelectronics, computer manufacturing, and physical devices. Advanced, high-performance computers, high-definition TV, digital camcorders, sensitive broadband imaging systems, flat-panel displays, robotic systems, and medical electronics and diagnostics are but a few examples of miniaturized device technologies that depend the utilization of thin film materials. The Handbook of Thin Films Materials is a comprehensive reference focusing on processing techniques, characterization methods, and physical properties of these thin film materials.

Download or read book Optical Properties of 2D Systems with Interacting Electrons written by Wolfgang J. Ossau and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of the NATO Advanced Research Workshop, held in St. Petersburg, Russia, 13-16 June 2002

Download or read book Diverse Quasiparticle Properties of Emerging Materials written by Tran Thi Thu Hanh and published by CRC Press. This book was released on 2022-10-07 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Diverse Quasiparticle Properties of Emerging Materials: First-Principles Simulations thoroughly explores the rich and unique quasiparticle properties of emergent materials through a VASP-based theoretical framework. Evaluations and analyses are conducted on the crystal symmetries, electronic energy spectra/wave functions, spatial charge densities, van Hove singularities, magnetic moments, spin configurations, optical absorption structures with/without excitonic effects, quantum transports, and atomic coherent oscillations. Key Features Illustrates various quasiparticle phenomena, mainly covering orbital hybridizations and spin-up/spin-down configurations Mainly focuses on electrons and holes, in which their methods and techniques could be generalized to other quasiparticles, such as phonons and photons Considers such emerging materials as zigzag nanotubes, nanoribbons, germanene, plumbene, bismuth chalcogenide insulators Includes a section on applications of these materials This book is aimed at professionals and researchers in materials science, physics, and physical chemistry, as well as upper-level students in these fields.

Download or read book Proceedings of 2000 International Conference on Excitonic Processes in Condensed Matter written by Kikuo Cho and published by World Scientific. This book was released on 2001 with total page 506 pages. Available in PDF, EPUB and Kindle. Book excerpt: At Yamada Conference LIII, papers on many novel materials and on novel phenomena in condensed matter physics were presented OCo for instance, the achievement of simultaneous creation of excitons and free-electron-hole pairs in rare gas solids, and a low frequency fluctuation of the spectral shift of indirect excitons in GaAs coupled quantum wells. Single molecule spectroscopy is a powerful tool for studying molecules including biological systems; the study of delocalization of excitons in the photosynthetic light harvesting antenna system was also reported. The proceedings thus contain many excellent papers dealing with current research topics on the excitonic processes in bulk, quantum wells, quantum dots and other confined systems. This book will serve as an excellent source of recent references and reviews for a wide range of researchers in physics, chemistry, engineering and biological sciences. The proceedings have been selected for coverage in: . OCo Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings). Contents: Dynamical Process of Photoionization in Semiconductor Nanocrystals (M Y Shen et al.); Excitons on a 1D Periodic Conjugated Polymer Chain: Two Electronic Structures of Polydiacetylene Chains (C Lapersonne-Meyer); Anomalous Spectral Shifts of Indirect Excitons in Coupled GaAs Quantum Wells (D W Snoke et al.); Infrared Absorption by Excitons in Cuprous Oxide (M GAppert et al.); Theory of Excitation-Energy Transfer Processes Involving Optically Forbidden Exciton States in Antenna Systems of Photosynthesis (K Mukai et al.); Transient Grating Induced by Excitonic Polaritons in Thin Film Semiconductors (K Akiyama et al.); Excitonic Photoluminescence of Pentacene Single Crystal (T Aoki-Matsumoto et al.); Scanning Near-Field Optical Microspectroscopy of Single Perylene Microcrystals (J Niitsuma et al.); and other papers. Readership: Condensed matter physicists, materials scientists, chemists and biologists."

Download or read book Electron Correlation and Quasiparticle Properties in Semiconductors Semiconductor Surfaces and Two dimensional Electron Systems written by Xuejun Zhu and published by . This book was released on 1992 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Excitonic Processes In Condensed Matter Proceedings Of 2000 International Conference Excon2000 written by Kikuo Cho and published by World Scientific. This book was released on 2001-08-22 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: At Yamada Conference LIII, papers on many novel materials and on novel phenomena in condensed matter physics were presented — for instance, the achievement of simultaneous creation of excitons and free-electron-hole pairs in rare gas solids, and a low frequency fluctuation of the spectral shift of indirect excitons in GaAs coupled quantum wells. Single molecule spectroscopy is a powerful tool for studying molecules including biological systems; the study of delocalization of excitons in the photosynthetic light harvesting antenna system was also reported. The proceedings thus contain many excellent papers dealing with current research topics on the excitonic processes in bulk, quantum wells, quantum dots and other confined systems. This book will serve as an excellent source of recent references and reviews for a wide range of researchers in physics, chemistry, engineering and biological sciences.The proceedings have been selected for coverage in:• Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)

Download or read book Optical Properties of Semiconductor Nanostructures written by Marcin L. Sadowski and published by Springer Science & Business Media. This book was released on 2000-06-30 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: Optical methods for investigating semiconductors and the theoretical description of optical processes have always been an important part of semiconductor physics. Only the emphasis placed on different materials changes with time. Here, a large number of papers are devoted to quantum dots, presenting the theory, spectroscopic investigation and methods of producing such structures. Another major part of the book reflects the growing interest in diluted semiconductors and II-IV nanosystems in general. There are also discussions of the fascinating field of photonic crystals. `Classical' low dimensional systems, such as GsAs/GaAlAs quantum wells and heterostructures, still make up a significant part of the results presented, and they also serve as model systems for new phenomena. New materials are being sought, and new experimental techniques are coming on stream, in particular the combination of different spectroscopic modalities.

Download or read book Optical properties of solids written by Frederick Wooten and published by Academic Pr. This book was released on 1972 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Inorganic Nanosheets and Nanosheet Based Materials written by Teruyuki Nakato and published by Springer. This book was released on 2017-04-18 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on inorganic nanosheets, including various oxides, chalcogenides, and graphenes, that provide two-dimensional (2D) media to develop materials chemistry in broad fields such as electronics, photonics, environmental science, and biology. The application area of nanosheets and nanosheet-based materials covers the analytical, photochemical, optical, biological, energetic, and environmental research fields. All of these applications come from the low dimensionality of the nanosheets, which anisotropically regulate structures of solids, microspaces, and fluids. Understanding nanosheets from chemical, structural, and application aspects in relation to their "fully nanoscopic" characters will help materials scientists to develop novel advanced materials. This is the first book that accurately and concisely summarizes this field including exfoliation and intercalation chemistries of layered crystals. The book provides perspective on the materials chemistry of inorganic nanosheets. The first section describes fundamental aspects of nanosheets common to diverse applications: how unique structures and properties are obtained from nanosheets based on low dimensionality. The second section presents state-of-the-art descriptions of how the 2D nature of nanosheets is utilized in each application of the materials that are developed.

Download or read book Handbook of Thin Film Materials Nanomaterials and magnetic thin films written by Hari Singh Nalwa and published by . This book was released on 2002 with total page 672 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Properties of Impurity States in Superlattice Semiconductors written by C.Y. Fong and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: A NATO workshop on "The Properties of Impurity States in Semiconductor Superlattices" was held at the University of Essex, Colchester, United Kingdom, from September 7 to 11, 1987. Doped semiconductor superlattices not only provide a unique opportunity for studying low dimensional electronic behavior, they can also be custom-designed to exhibit many other fascinating el~ctronic properties. The possibility of using these materials for new and novel devices has further induced many astonishing advances, especially in recent years. The purpose of this workshop was to review both advances in the state of the art and recent results in various areas of semiconductor superlattice research, including: (i) growth and characterization techniques, (ii) deep and shallow im purity states, (iii) quantum well states, and (iv) two-dimensional conduction and other novel electronic properties. This volume consists of all the papers presented at the workshop. Chapters 1-6 are concerned with growth and characterization techniques for superlattice semiconductors. The question of a-layer is also discussed in this section. Chapters 7-15 contain a discussion of various aspects of the impurity states. Chapters 16- 22 are devoted to quantum well states. Finally, two-dimensional conduction and other electronic properties are described in chapters 23-26.