Download or read book Phase Transitions in Transition Metal Dichalcogenides Studied by Femtosecond Electron Diffraction written by Kerstin Haupt and published by . This book was released on 2013 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Femtosecond Electron Diffraction Studies of Strongly driven Structural Phase Transitions microform written by Bradley John Siwick and published by National Library of Canada = Bibliothèque nationale du Canada. This book was released on 2004 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: The new technique of femtosecond electron diffraction is developed and applied to the study of an ultrafast structural phase transition. A combination of numerical and analytical modeling is used to obtain a comprehensive understanding of the space-charge dominated propagation dynamics of high number density femtosecond electron pulses and to design a novel photoactivated electron gun. This electron source, capable of producing sub-500 femtosecond electron pulses with sufficient brightness to allow the study of even irreversible structural dynamics, is employed to investigate the strongly driven, laser-induced solid-to-liquid phase transition in polycrystalline aluminum. We are able to see, in real time, the loss of the long-range order present in the crystalline phase and the emergence of the liquid structure where only short-range atomic correlations are present; this transition occurs in 3.5 ps for thin-film aluminum with an excitation fluence of 70 mJ/cm2. The sensitivity and temporal resolution was sufficient to capture the time-dependent atomic pair correlation function as the material evolved from the solid to liquid state. These observations provide an atomic level description of the melting process in which the dynamics are best understood as a thermal phase transition under strongly driven conditions.

Download or read book Structural Phase Transitions in Layered Transition Metal Compounds written by K. Motizuki and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structural phase transition is one of the most fundamental problems in solid state physics. Layered transition-metal dichalcogenides provide us with a most exciting area for the study of structural phase transitions that are associated with the charge density wave (CDW). A large variety of structural phase transitions, such as commensurate and incommensurate transitions, and the physical proper ties related to the formation of a CDW, have been an object of intense study made for many years by methods employing modem microscopic techniques. Rather recently, efforts have been devoted to the theoretical understanding of these experimental results. Thus, McMillan, for example, has developed an elegant phenomenological theory on the basis of the Landau free energy expansion. An extension of McMillan's theory has provided a successful understanding of the successive phase transitions observed in the IT- and 2H-compounds. In addition, a microscopic theory of lattice instability, lattice dynamics, and lattice distortion in the CDW state of the transition-metal dichalcogenides has been developed based on their electronic structures. As a result, the driving force of the CDW formation in the IT- and 2H-compounds has become clear. Furthermore, the effect of lattice fluctuations on the CDW transition and on the anomalous behavior of various physical properties has been made clear microscopically.

Download or read book Structural Phase Transitions in Layered Transition Metal Compounds written by K Motizuki and published by . This book was released on 1986-10-31 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photoinduced Phase Transitions written by K. Nasu and published by World Scientific. This book was released on 2004 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new class of insulating solids was recently discovered. Whenirradiated by a few visible photons, these solids give rise to amacroscopic excited domain that has new structural and electronicorders quite different from the starting ground state. This occurrenceis called photoinduced phase transition, and this multi-authoredbook reviews recent theoretical and experimental studies of this newphenomenon.

Download or read book Two Dimensional Transition Metal Dichalcogenides written by Alexander V. Kolobov and published by Springer. This book was released on 2016-07-26 with total page 545 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book summarizes the current status of theoretical and experimental progress in 2 dimensional graphene-like monolayers and few-layers of transition metal dichalcogenides (TMDCs). Semiconducting monolayer TMDCs, due to the presence of a direct gap, significantly extend the potential of low-dimensional nanomaterials for applications in nanoelectronics and nano-optoelectronics as well as flexible nano-electronics with unprecedented possibilities to control the gap by external stimuli. Strong quantum confinement results in extremely high exciton binding energies which forms an interesting platform for both fundamental studies and device applications. Breaking of spatial inversion symmetry in monolayers results in strong spin-valley coupling potentially leading to their use in valleytronics. Starting with the basic chemistry of transition metals, the reader is introduced to the rich field of transition metal dichalcogenides. After a chapter on three dimensional crystals and a description of top-down and bottom-up fabrication methods of few-layer and single layer structures, the fascinating world of two-dimensional TMDCs structures is presented with their unique atomic, electronic, and magnetic properties. The book covers in detail particular features associated with decreased dimensionality such as stability and phase-transitions in monolayers, the appearance of a direct gap, large binding energy of 2D excitons and trions and their dynamics, Raman scattering associated with decreased dimensionality, extraordinarily strong light-matter interaction, layer-dependent photoluminescence properties, new physics associated with the destruction of the spatial inversion symmetry of the bulk phase, spin-orbit and spin-valley couplings. The book concludes with chapters on engineered heterostructures and device applications such as a monolayer MoS2 transistor. Considering the explosive interest in physics and applications of two-dimensional materials, this book is a valuable source of information for material scientists and engineers working in the field as well as for the graduate students majoring in materials science.

Download or read book Two Dimensional Transition Metal Dichalcogenides written by Chi Sin Tang and published by John Wiley & Sons. This book was released on 2023-11-14 with total page 357 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two-Dimensional Transition-Metal Dichalcogenides Comprehensive resource covering rapid scientific and technological development of polymorphic two-dimensional transition-metal dichalcogenides (2D-TMDs) over a range of disciplines and applications Two-Dimensional Transition-Metal Dichalcogenides: Phase Engineering and Applications in Electronics and Optoelectronics provides a discussion on the history of phase engineering in 2D-TMDs as well as an in-depth treatment on the structural and electronic properties of 2D-TMDs in their respective polymorphic structures. The text addresses different forms of in-situ synthesis, phase transformation, and characterization methods for 2D-TMD materials and provides a comprehensive treatment of both the theoretical and experimental studies that have been conducted on 2D-TMDs in their respective phases. Two-Dimensional Transition-Metal Dichalcogenides includes further information on: Thermoelectric, fundamental spin-orbit structures, Weyl semi-metallic, and superconductive and related ferromagnetic properties that 2D-TMD materials possess Existing and prospective applications of 2D-TMDs in the field of electronics and optoelectronics as well as clean energy, catalysis, and memristors Magnetism and spin structures of polymorphic 2D-TMDs and further considerations on the challenges confronting the utilization of TMD-based systems Recent progress of mechanical exfoliation and the application in the study of 2D materials and other modern opportunities for progress in the field Two-Dimensional Transition-Metal Dichalcogenides provides in-depth review introducing the electronic properties of two-dimensional transition-metal dichalcogenides with updates to the phase engineering transition strategies and a diverse range of arising applications, making it an essential resource for scientists, chemists, physicists, and engineers across a wide range of disciplines.

Download or read book The Physics of Structural Phase Transitions written by Minoru Fujimoto and published by Springer Science & Business Media. This book was released on 2004-09-01 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Phase transitions in which crystalline solids undergo structural changes present an interesting problem in the interplay between the crystal structure and the ordering process. This text, intended for readers with some prior knowledge of condensed-matter physics, emphasizes the basic physics behind such spontaneous structural changes in crystals. Starting with the relevant thermodynamic principles, the book discusses the nature of order variables and their collective motion in a crystal lattice; in a structural phase transition a singularity in such a collective mode is responsible for the lattice instability, as revealed by soft phonons. This mechanism is analogous to the interplay of a charge-density wave and a periodically deformed lattice in low-dimensional conductors. The text also describes experimental methods for modulated crystal structures and gives examples of structural changes in representative systems. The book is divided into two parts. The first, theoretical, part includes such topics as: the Landau theory of phase transitions; statistics, correlations and the mean-field approximation; pseudospins and their collective modes; soft lattice modes and pseudospin condensates; lattice imperfections and their role in the phase transitions of real crystals. The second part discusses experimental studies of modulated crystals using x-ray diffraction, neutron inelastic scattering, light scattering, dielectric measurements, and magnetic resonance spectroscopy.

Download or read book Electron Diffraction Study of Transition Metal Dichalcogenides written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Photoinduced Phase Transitions Studied by Femtosecond Single shot Spectroscopy written by Taeho Shin and published by . This book was released on 2010 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single-shot femtosecond spectroscopy has been developed and employed for the study of phase transitions of solid-state materials. Using two crossed echelons, a two dimensional spatial delay gradient was generated across a single probe pulse profile. This novel scheme enables us to monitor irreversible change in solids by acquiring many time-resolved data points with a single laser pulse. With the integration with a non-collinear optical parametric amplifier (NOPA) and a conventional pump-probe instrument, ultrafast dynamics of coherent lattice vibrations and photo-induced phase transitions were examined in two different systems. Ultrafast dynamics such as coherent lattice vibrations and bond softening were investigated for Bi thin films and bulk single crystals. Depending on the thickness, transient reflectivity was changed significantly. The variations are ascribed to different electronic structures possibly originating from quantum confinement. Bond softening exhibits a strong thickness dependence due to hot carrier dynamics as well as to the different electronic structures. At high pump fluences, no phonon oscillations were observed suggesting a phase transition to liquid or to a higher symmetry crystalline phase (reverse Peierls distortion). Together with thermal modeling, double pump measurements reveal nonthermal melting occurring in bulk and thin Bi films. A higher threshold fluence for nonthermal melting is observed in bulk bismuth as compared to thin films, suggesting ultrafast carrier dynamics such as ballistic transport. In addition to nonthermal effects, thermal effects such as inelastic electron-phonon scattering and nonradiative recombination play a crucial role in melting and cooling at later times after nonthermal melting takes place. A quasi one-dimensional platinum iodide complex showed strong oscillations in reflectivity which are attributed to oscillatory motions of wave packets on a selftrapped exciton (STE) potential surface., As optical excitation increased, electron transfer from Pt 2+ to an adjacent Pt4+ occurred over a wider range of lattice sites and weakened the oscillations. Above a certain pump fluence, oscillations disappeared completely indicating that the mixed valence, charge density wave state changed to monovalent, Mott-Hubbard phase. The reverse phase transition, i.e., from the MottHubbard phase to the charge density wave state began within 3 ps of the optical pump.

Download or read book Femtosecond Electron Diffraction Using Relativistic Electron Pulses written by Jinfeng Yang and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Observation of atomic-scale structural motion in matter with femtosecond temporal resolution is of considerable interest to scientists and paves the way for new science and applications. For this purpose, ultrafast electron diffraction (UED) imaging using femtosecond electron pulses is a very promising technique, as electrons have a larger elastic scattering cross section as compared to photons or X-rays and can be easily focused in observation with high spatial resolution. In this chapter, we first give an overview of the historical development of current nonrelativistic UEDs and discuss the potentials of UEDs with relativistic electron pulses. Second, we describe the concept and development of relativistic UED with femtosecond electron pulses generated by a radio-frequency acceleration-based photoemission gun. Some demonstrations of diffraction imaging of crystalline materials using 3-MeV electron pulses with durations of ,ào100¬†fs are presented. Finally, we report a methodology of single-shot time-resolved diffraction imaging for the study of ultrafast dynamics of photo-induced irreversible phase transitions.

Download or read book Phase Transitions and Relaxation in Systems with Competing Energy Scales written by T. Riste and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Systems with competing energy scales are widespread and exhibit rich and subtle behaviour, although their systematic study is a relatively recent activity. This text presents lectures given at a NATO Advanced Study Institute reviewing the current knowledge and understanding of this fascinating subject, particularly with regard to phase transitions and dynamics, at an advanced tutorial level. Both general and specific aspects are considered, with competitions having several origins; differences in intrinsic interactions, interplay between intrinsic and extrinsic effects, such as geometry and disorder; irreversibility and non-equilibration. Among the specific physical application areas are supercooled liquids and glasses, high-temperature superconductors, flux or vortex pinning and motion, charge density waves, domain growth and coarsening, and electron solidification.

Download or read book Surface Phase Transitions Studied with Low Energy Electron Diffraction written by Robert Quek Hwang and published by . This book was released on 1989 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Phase Transitions and Crystal Symmetry written by I͡Uriĭ Aleksandrovich Izi͡umov and published by Springer Science & Business Media. This book was released on 1990 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt: About half a century ago Landau formulated the central principles of the phe nomenological second-order phase transition theory which is based on the idea of spontaneous symmetry breaking at phase transition. By means of this ap proach it has been possible to treat phase transitions of different nature in altogether distinct systems from a unified viewpoint, to embrace the aforemen tioned transitions by a unified body of mathematics and to show that, in a certain sense, physical systems in the vicinity of second-order phase transitions exhibit universal behavior. For several decades the Landau method has been extensively used to an alyze specific phase transitions in systems and has been providing a basis for interpreting experimental data on the behavior of physical characteristics near the phase transition, including the behavior of these characteristics in systems subject to various external effects such as pressure, electric and magnetic fields, deformation, etc. The symmetry aspects of Landau's theory are perhaps most effective in analyzing phase transitions in crystals because the relevant body of mathemat ics for this symmetry, namely, the crystal space group representation, has been worked out in great detail. Since particular phase transitions in crystals often call for a subtle symmetry analysis, the Landau method has been continually refined and developed over the past ten or fifteen years.

Download or read book Phase Transitions in Materials written by Brent Fultz and published by Cambridge University Press. This book was released on 2020-05-14 with total page 609 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This book explains the thermodynamics and kinetics of most of the important phase transitions in materials science. It is a textbook, so the emphasis is on explanations of phenomena rather than a scholarly assessment of their origins. The goal is explanations that are concise, clear, and reasonably complete. The level and detail are appropriate for upper division undergraduate students and graduate students in materials science andmaterials physics. The book should also be useful for researchers who are not specialists in these fields. The book is organized for approximately sequential coverage in a graduate-level course. The four parts of the book serve different purposes, however, and should be approached differently"--

Download or read book Structural Dynamics of the Metal insulator Transition in VO2 written by Vance Morrison and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis the design and implementation of an ultrafast electron diffractometer with radio frequency compression capabilities is presented. In addition, the results of ultrafast electron diffraction (UED) measurements on the semiconductor to metal phase transition in vanadium dioxide are shown. The ability to perform UED measurements on ultrafast time scales is first demonstrated by observing the expansion and coherent oscillation of the crystal lattice in thin film, single crystal gold. The evolution of the spatio-temporal charge density in ultrashort pulses was then studied using electron-laser cross correlation measurements mediated by the ponderomotive force. These measurements were compared with particle tracing simulations and theoretical models. Similar electron-laser cross correlation measurements were also performed in order to characterize the behaviour of a novel radio-frequency (RF) pulse compression technique. Using an RF cavity, an oscillating, 3 GHz electric field is synchronized to the electron pulse arrival time and allows for the compression of high bunch charge electron pulses (0.1 pC) to 334+/-10 fs. This represents a bunch charge increase of 10^2-10^3 over previous ultrafast electron sources that provide a sub 500 fs impulse response. Finally, the semiconductor to metal transition in vanadium dioxide was studied using RF compressed electron pulses. Here, distinct ultrafast structural and electronic phase transitions were observed providing insight into the long standing debate surrounding the roles of electron-electron interactions and electron-lattice interactions in this phase transition." --

Download or read book Low Energy Electron Diffraction Studies of Phase Transformations at Metal Surfaces written by Richard Martin Goodman and published by . This book was released on 1969 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: