Nonequilibrium Dynamics of Collective Excitations in Quantum Materials


Book Description

This book studies the dynamics of fundamental collective excitations in quantum materials, focusing on the use of state-of-the-art ultrafast broadband optical spectroscopy. Collective behaviour in solids lies at the origin of several cooperative phenomena that can lead to profound transformations, instabilities and phase transitions. Revealing the dynamics of collective excitations is a topic of pivotal importance in contemporary condensed matter physics, as it provides information on the strength and spatial distribution of interactions and correlation. The experimental framework explored in this book relies on setting a material out-of-equilibrium by an ultrashort laser pulse and monitoring the photo-induced changes in its optical properties over a broad spectral region in the visible or deep-ultraviolet. Collective excitations (e.g. plasmons, excitons, phonons...) emerge either in the frequency domain as spectral features across the probed range, or in the time domain as coherent modes triggered by the pump pulse. Mapping the temporal evolution of these collective excitations provides access to the hierarchy of low-energy phenomena occurring in the solid during its path towards thermodynamic equilibrium. This methodology is used to investigate a number of strongly interacting and correlated materials with an increasing degree of internal complexity beyond conventional band theory.




Quantum Gases


Book Description

This volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics.




Emergent States in Photoinduced Charge-Density-Wave Transitions


Book Description

This book advances understanding of light-induced phase transitions and nonequilibrium orders that occur in a broken-symmetry system. Upon excitation with an intense laser pulse, materials can undergo a nonthermal transition through pathways different from those in equilibrium. The mechanism underlying these photoinduced phase transitions has long been researched, but many details in this ultrafast, non-adiabatic regime still remain to be clarified. The work in this book reveals new insights into this phenomena via investigation of photoinduced melting and recovery of charge density waves (CDWs). Using several time-resolved diffraction and spectroscopic techniques, the author shows that the light-induced melting of a CDW is characterized by dynamical slowing-down, while the restoration of the symmetry-breaking order features two distinct timescales: A fast recovery of the CDW amplitude is followed by a slower re-establishment of phase coherence, the latter of which is dictated by the presence of topological defects in the CDW. Furthermore, after the suppression of the original CDW by photoexcitation, a different, competing CDW transiently emerges, illustrating how a hidden order in equilibrium can be unleashed by a laser pulse. These insights into CDW systems may be carried over to other broken-symmetry states, such as superconductivity and magnetic ordering, bringing us one step closer towards manipulating phases of matter using a laser pulse.




Quantum Gases: Finite Temperature And Non-equilibrium Dynamics


Book Description

The 1995 observation of Bose-Einstein condensation in dilute atomic vapours spawned the field of ultracold, degenerate quantum gases. Unprecedented developments in experimental design and precision control have led to quantum gases becoming the preferred playground for designer quantum many-body systems.This self-contained volume provides a broad overview of the principal theoretical techniques applied to non-equilibrium and finite temperature quantum gases. Covering Bose-Einstein condensates, degenerate Fermi gases, and the more recently realised exciton-polariton condensates, it fills a gap by linking between different methods with origins in condensed matter physics, quantum field theory, quantum optics, atomic physics, and statistical mechanics. Thematically organised chapters on different methodologies, contributed by key researchers using a unified notation, provide the first integrated view of the relative merits of individual approaches, aided by pertinent introductory chapters and the guidance of editorial notes.Both graduate students and established researchers wishing to understand the state of the art will greatly benefit from this comprehensive and up-to-date review of non-equilibrium and finite temperature techniques in the exciting and expanding field of quantum gases and liquids./a




Ultrafast Electronic and Structural Dynamics


Book Description

Zusammenfassung: This book illustrates advanced technologies for imaging electrons and atoms in action in various forms of matter, from atoms and diatoms to protein molecules and condensed matter. The technologies that are described employ ultrafast pulsed lasers, X-ray free electron lasers, and pulsed electron guns, with pulse durations from femtoseconds, suitable to visualize atoms in action, to attoseconds, needed to visualize ballistic electron motion. Advanced theories, indispensable for understanding such ultrafast imaging and spectroscopy data on electrons and atoms in action, are also described. The book consists of three parts. The first part describes probing methods of attosecond electron dynamics in atoms, molecules, liquids, and solids. The second part describes femtosecond structural dynamics and coupling of structural change and electron motion in molecules and solids The last part is dedicated to ultrafast photophysical processes and chemical reactions of protein molecules responsible for biological functions




Spectroscopy and Dynamics of Collective Excitations in Solids


Book Description

This book presents the proceedings of the course "Spectroscopy and Dynamics of Collective Excitations in Solids" held in Erice, Italy from June 17 to July 1, 1995. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The purpose of this course was to present and discuss physical models, mathematical formalisms, experimental techniques and applications relevant to the subject of collective excitations in solids. By bringing together specialists in the field of solid state spectroscopy, this course provided a much needed forum for the critical assessment and evaluation of recent and past developments in the physics of solids. A total of 83 participants came from 57 laboratories and 20 different countries (Austria, Belgium, Brazil, Denmark, Finland, France, Germany, Greece, Israel, Italy, Japan, The Netherlands, Norway, Portugal, Russia, Spain, Switzerland, Turkey, the United Kingdom, and the United States). The secretaries of the course were Stamatios K yrkos and Daniel Di Bartolo. 45 lectures divided in 13 series were given. In addition 8 (one or two-hour) "long seminars," 1 "special lecture," 2 interdisciplinary lectures, 29 "short seminars," and 16 posters were presented. The sequence of lectures was in accordance with the logical development of the subject of the meeting. Each lecturer started at a rather fundamental level and ultimately reached the frontier of knowledge in the field.




Quantum Many-Body Physics in Open Systems: Measurement and Strong Correlations


Book Description

This book studies the fundamental aspects of many-body physics in quantum systems open to an external world. Recent remarkable developments in the observation and manipulation of quantum matter at the single-quantum level point to a new research area of open many-body systems, where interactions with an external observer and the environment play a major role. The first part of the book elucidates the influence of measurement backaction from an external observer, revealing new types of quantum critical phenomena and out-of-equilibrium dynamics beyond the conventional paradigm of closed systems. In turn, the second part develops a powerful theoretical approach to study the in- and out-of-equilibrium physics of an open quantum system strongly correlated with an external environment, where the entanglement between the system and the environment plays an essential role. The results obtained here offer essential theoretical results for understanding the many-body physics of quantum systems open to an external world, and can be applied to experimental systems in atomic, molecular and optical physics, quantum information science and condensed matter physics.




Collective Effects in Quantum Statistics of Radiation and Matter


Book Description

Material particles, electrons, atoms, molecules, interact with one another by means of electromagnetic forces. That is, these forces are the cause of their being combined into condensed (liquid or solid) states. In these condensed states, the motion of the particles relative to one another proceeds in orderly fashion; their individual properties as well as the electric and magnetic dipole moments and the radiation and absorption spectra, ordinarily vary little by comparison with their properties in the free state. Exceptiotls are the special so-called collective states of condensed media that are formed under phase transitions of the second kind. The collective states of matter are characterized to a high degree by the micro-ordering that arises as a result of the interaction between the particles and which is broken down by chaotic thermal motion under heating. Examples of such pheonomena are the superfluidity of liquid helium, and the superconductivity and ferromagnetism of metals, which exist only at temperatures below the critical temperature. At low temperature states the particles do not exhibit their individual characteristics and conduct themselves as a single whole in many respects. They flow along capillaries in ordered fashion and create an undamped current in a conductor or a macroscopic magnetic moment. In this regard the material acquires special properties that are not usually inherent to it.




Understanding Properties of Atoms, Molecules and Materials


Book Description

In a technology driven civilization the quest for new and smarter materials is everlasting. They are required as platforms for developing new technologies or for improving an already existing technology. The discovery of a new material is no longer chance driven or accidental, but is based on careful reasoning structured by deep understanding of the microconstituents of materials - the atoms and molecules in isolation or in an assembly. That requires fair amount of exposure to quantum and statistical mechanics. `Understanding Properties of Atoms, Molecules and Materials' is an effort (perhaps the first ever) to bring all the necessary theoretical ingredients and relevant physical information in a single volume. The book introduces the readers (first year graduates) or researchers in material chemistry/engineering to elementary quantum mechanics of atoms, molecules and solids and then goes on to make them acquainted with methods of statistical mechanics (classical as well as quantum) along with elementary principles of classical MD simulation. The basic concepts are introduced with clarity and illustrated with easy to grasp examples, thus preparing the readers for an exploration through the world of materials - the exotic and the mundane. The emphasis has been on the phenomena and what shapes them at the fundamental level. A comprehensive description of modern designing principles for materials with examples is a unique feature of the book. The highlights of the book are comprehensive introduction and analysis of Quantum states of atoms and molecules The translational symmetry and quantum states in periodic and amorphous solids Band structure and tuning Classical and quantum statistics with applications to ideal gases (photons, phonons and electrons, molecules) Quantum states in type-I and type-II superconductors (elementary theory included) Magnetic materials, materials with GMR and CMR Shape memory effects in alloys and materials 2D materials (graphene and graphene analogus) NLO and photovoltaic materials Hydrogen storage material for mitigating the looming energy crisis Quantum states in low and high band gap semiconductors Semimetals Designer materials, etc. The volume is designed and organized to create interest in the science of materials and the silent revolution that is redefining the goals and boundaries of materials science continuously.




Quantum Field Theory of Non-equilibrium States


Book Description

Quantum field theory is the application of quantum mechanics to systems with infinitely many degrees of freedom. This 2007 textbook presents quantum field theoretical applications to systems out of equilibrium. It introduces the real-time approach to non-equilibrium statistical mechanics and the quantum field theory of non-equilibrium states in general. It offers two ways of learning how to study non-equilibrium states of many-body systems: the mathematical canonical way and an easy intuitive way using Feynman diagrams. The latter provides an easy introduction to the powerful functional methods of field theory, and the use of Feynman diagrams to study classical stochastic dynamics is considered in detail. The developed real-time technique is applied to study numerous phenomena in many-body systems. Complete with numerous exercises to aid self-study, this textbook is suitable for graduate students in statistical mechanics and condensed matter physics.