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Author: Jonathan A. Sobota Publisher: ISBN: Category : Languages : en Pages :
Book Description
Most macroscopic properties of a material (electrical, thermal, and optical) can be understood on the basis of its band structure and the dynamical behavior of its electrons. However, resolving electron dynamics directly is difficult using conventional techniques because the underlying interactions typically occur on a femtosecond timescale. Ultrafast photoemission spectroscopy is an experimental technique which can probe electronic band structure with femtosecond time resolution. This dissertation presents work using this technique to study dynamic phenomena in the topological insulator Bi2Se3, a fascinating material due to the coexistence of its insulating bulk and metallic surface electronic structures. It will demonstrate three types of novel measurements that can be performed with ultrafast photoemission spectroscopy which are unattainable by other methods: (1) By performing two-photon photoemission (2PPE) spectroscopy, it is possible to resolve unoccupied band structure above the Fermi level. In Bi2Se3 this reveals a second, topologically protected surface state. (2) Time-resolved 2PPE (tr2PPE) is used to record real-time "movies" of the electron relaxation which follows optical excitation. This allows for the identification of intra- and inter- band electron scattering pathways in the material. Temperature-dependent tr2PPE measurements are performed on the conduction band to help understand the role of electron-phonon coupling. A model of fundamental electron-phonon scattering processes is implemented to describe the results. (3) In a time- and angle- resolved photoemission spectroscopy (trARPES) experiment, intense optical excitation is used to drive coherent motion of A1g optical phonon modes in Bi2Se3. These modes lead to periodic binding energy shifts in the bulk conduction band and surface state. A slight red-shift of the phonon frequency is observed in the surface state, which is used to deduce a softening of the phonon due to the abrupt termination of the crystal at its surface.
Author: Jonathan A. Sobota Publisher: ISBN: Category : Languages : en Pages :
Book Description
Most macroscopic properties of a material (electrical, thermal, and optical) can be understood on the basis of its band structure and the dynamical behavior of its electrons. However, resolving electron dynamics directly is difficult using conventional techniques because the underlying interactions typically occur on a femtosecond timescale. Ultrafast photoemission spectroscopy is an experimental technique which can probe electronic band structure with femtosecond time resolution. This dissertation presents work using this technique to study dynamic phenomena in the topological insulator Bi2Se3, a fascinating material due to the coexistence of its insulating bulk and metallic surface electronic structures. It will demonstrate three types of novel measurements that can be performed with ultrafast photoemission spectroscopy which are unattainable by other methods: (1) By performing two-photon photoemission (2PPE) spectroscopy, it is possible to resolve unoccupied band structure above the Fermi level. In Bi2Se3 this reveals a second, topologically protected surface state. (2) Time-resolved 2PPE (tr2PPE) is used to record real-time "movies" of the electron relaxation which follows optical excitation. This allows for the identification of intra- and inter- band electron scattering pathways in the material. Temperature-dependent tr2PPE measurements are performed on the conduction band to help understand the role of electron-phonon coupling. A model of fundamental electron-phonon scattering processes is implemented to describe the results. (3) In a time- and angle- resolved photoemission spectroscopy (trARPES) experiment, intense optical excitation is used to drive coherent motion of A1g optical phonon modes in Bi2Se3. These modes lead to periodic binding energy shifts in the bulk conduction band and surface state. A slight red-shift of the phonon frequency is observed in the surface state, which is used to deduce a softening of the phonon due to the abrupt termination of the crystal at its surface.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Using femtosecond time- and angle-resolved photoemission spectroscopy, we investigated the nonequilibrium dynamics of the topological insulator Bi2Se3. We studied p-type Bi2Se3, in which the metallic Dirac surface state and bulk conduction bands are unoccupied. Optical excitation leads to a meta-stable population at the bulk conduction band edge, which feeds a nonequilibrium population of the surface state persisting for>10 ps. This unusually long-lived population of a metallic Dirac surface state with spin texture may present a channel in which to drive transient spin-polarized currents.
Author: Jiajun Zhu Publisher: Anchor Academic Publishing ISBN: 3960671601 Category : Science Languages : en Pages : 91
Book Description
Topological insulator is one of the hottest research topics in solid state physics. This is the first book to describe the vibrational spectroscopies and electrical transport of topological insulator Bi2Se3, one of the most exciting areas of research in condensed matter physics. In particular, attempts have been made to summarize and develop the various theories and new experimental techniques developed over years from the studies of Raman scattering, infrared spectroscopy and electrical transport of topological insulator Bi2Se3. It is intended for material and physics researchers and graduate students doing research in the field of optical and electrical properties of topological insulators, providing them the physical understanding and mathematical tools needed to engage research in this quickly growing field. Some key topics in the emerging field of topological insulators are introduced.
Author: Andrew Patton Weber Publisher: ISBN: Category : Bismuth Languages : en Pages : 148
Book Description
As the size of a solid shrinks, the ratio of surface area to bulk volume grows and surface effects become more important. In a world where technologies advance with the shrinking size of electronic devices, one phase of matter has emerged which is fit for the near future of surface-dominated performance. Moreover, it has brought a new set of ideas to solid-state physics and chemistry, especially the understanding that the discipline of topology can be applied to classify the electron band structures. The topological insulator phase yields an exotic metal surface state in which the orientation of the electron's spin is locked perpendicular to its momentum. This property suppresses backscattering (making it possible to pass spin-polarized currents through the material without loss), offers a crucial ingredient for innovative approaches to quantum computation, and provides the basis for observing unique magnetoelectric effects. However, the surface states of materials in the topological insulator phase can wildly differ, so it is of interest to systematically characterize new materials to understand how the structure in position-space is related to the spin-resolved structure of electrons in energy- and momentum-space. We will discuss this relationship as it is probed through spin- and angle-resolved photoemission spectroscopy experiments on three topological (Bi2)m(Bi2Se3)n superlattices: (a) Bi2Se3 (m = 0, n = 1), (b) Bi4Se3 (m = 1, n = 1), and (c) BiSe (m = 1, n = 2). Our studies have not only proven the topological nature of these materials, but also demonstrate how bulk band structure and polar chemical bonding control the surface meta's concentration, dispersion, and spin-orbital character. Case (a) is considered to provide an ideal model of the topological surface metal. Case (b) provides the three important findings: (1) the chemical identity of the surface-termination controls the orbital composition and energy distribution of the surface states, (2) there are two topological states in sequential bulk band gaps, (3) of these, one of topological state undergoes a hybridization effect that yields a momentum-dependent gap in the band structure as large as 85 meV. Case (c) has a practical significance in that the surface metal has a potentially record-breaking carrier density of ~1013cm−2 (estimated from the Fermi surface area), more than an order of magnitude higher than in Bi2Se3. This occurs as a result of charge transfer from the Bi2 layers to the Bi2Se3 layers.
Author: Turgut Yilmaz Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
Ph.D. Dissertation Turgut Yilmaz Graduate Student UConn Department of Physics "Photoemission Studies of Topological Insulators" Topological insulators (TIs) attracted scientist due to its distinct electronic structure. TIs possess metallic surfaces due to strong spin orbit coupling, while the bulk shows the insulating behavior. On the surface of TIs topologically protected surface states by time reversal symmetry (TRS) obeys the massless Dirac equation. One of the interest on TIs is to introduce magnetic impurities into bulk and on the surface to break TRS leading to open an energy gap at the Dirac point of TIs. Therefore, x-ray photoemission spectroscopy (XPS) and angle resolved photoemission spectroscopy (ARPES) study on Cr bulk and surface doped Bi2Se3 were presented in order to investigate magnetic impurity doping impact on the electronic and chemical environment of Bi2Se3. ARPES measurements revealed that Cr bulk doping opens an energy gap at the Dirac point without ferromagnetism, while gapless surface states are robust against Cr surface deposition. Another interest on TIs is to obtain proximity induced superconductivity in order to open experimental avenue for possible experimental detection of Majorana fermions. Therefore, we presented ARPES study on Bi2Se3/ Bi2Sr2CaCu2O8+Î ́ (BSCCO) heterostructure in order to search for proximity induced superconductivity. In contrast to expectations, ARPES measurements do not show any sign of the proximity induced superconductivity in the thickness range from 0.5 quintuple layer of Bi2Se3 to 15 quintuple layer of Bi2Se3.
Author: Eryin Wang Publisher: Springer Nature ISBN: 981151447X Category : Technology & Engineering Languages : en Pages : 90
Book Description
This book focuses on angle-resolved photoemission spectroscopy studies on novel interfacial phenomena in three typical two-dimensional material heterostructures: graphene/h-BN, twisted bilayer graphene, and topological insulator/high-temperature superconductors. Since the discovery of graphene, two-dimensional materials have proven to be quite a large “family”. As an alternative to searching for other family members with distinct properties, the combination of two-dimensional (2D) materials to construct heterostructures offers a new platform for achieving new quantum phenomena, exploring new physics, and designing new quantum devices. By stacking different 2D materials together and utilizing interfacial periodical potential and order-parameter coupling, the resulting heterostructure’s electronic properties can be tuned to achieve novel properties distinct from those of its constituent materials. This book offers a valuable reference guide for all researchers and students working in the area of condensed matter physics and materials science.
Author: Publisher: Elsevier ISBN: 0128098945 Category : Science Languages : en Pages : 5276
Book Description
Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry, Seven Volume Set summarizes current, fundamental knowledge of interfacial chemistry, bringing readers the latest developments in the field. As the chemical and physical properties and processes at solid and liquid interfaces are the scientific basis of so many technologies which enhance our lives and create new opportunities, its important to highlight how these technologies enable the design and optimization of functional materials for heterogeneous and electro-catalysts in food production, pollution control, energy conversion and storage, medical applications requiring biocompatibility, drug delivery, and more. This book provides an interdisciplinary view that lies at the intersection of these fields. Presents fundamental knowledge of interfacial chemistry, surface science and electrochemistry and provides cutting-edge research from academics and practitioners across various fields and global regions
Author: Takayoshi Kobayashi Publisher: CRC Press ISBN: 0429591721 Category : Medical Languages : en Pages : 708
Book Description
This book describes the basic physical principles of techniques to generate and ultrashort pulse lasers and applications to ultrafast spectroscopy of various materials covering chemical molecular compounds, solid-state materials, exotic novel materials including topological materials, biological molecules and bio- and synthetic polymers. It introduces non-linear optics which provides the basics of generation and measurement of pulses and application examples of ultrafast spectroscopy to solid state physics. Also it provide not only material properties but also material processing procedures. The book describes also details of the world shortest visible laser and DUV lasers developed by the author’s group. It is composed of the following 12 Sections: The special features of this book is that it is written by a single author with a few collaborators in a systematic way. Hence it provides a comprehensive and systematic description of the research field of ultrashort pulse lasers and ultrafast spectroscopy. Generation of ultrashort pulses in deep ultraviolet to near infrared Generation of ultrashort pulses in terahertz Carrier envelope phase (CEP) Simple NLO processes with a few colors Multi-color involved NLO processes Multi-color ultrashort pulse generation NLO materials NLO processes in time-resolved spectroscopy Low dimension materials Conductors and superconductors Chemical reactions and material processing Photobiological reactions
Author: Young Min Jhon Publisher: Elsevier ISBN: 0128186593 Category : Technology & Engineering Languages : en Pages : 413
Book Description
2D Materials for Nanophotonics presents a detailed overview of the applications of 2D materials for nanophotonics, covering the photonic properties of a range of 2D materials including graphene, 2D phosphorene and MXenes, and discussing applications in lighting and energy storage. This comprehensive reference is ideal for readers seeking a detailed and critical analysis of how 2D materials are being used for a range of photonic and optical applications. - Outlines the major photonic properties in a variety of 2D materials - Demonstrates major applications in lighting and energy storage - Explores the challenges of using 2D materials in photonics
Author: Jonathan A. Sobota
Author: Jonathan A. Sobota
Author: 
Author: Jiajun Zhu
Author: Andrew Patton Weber
Author: Yuqi Xia
Author: Turgut Yilmaz
Author: Eryin Wang
Author: 
Author: Takayoshi Kobayashi
Author: Young Min Jhon