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.

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.

Advanced spectroscopic techniques allow the probing of very small systems and very fast phenomena, conditions that can be considered "extreme" at the present status of our experimentation and knowledge. Quantum dots, nanocrystals and single molecules are examples of the former and events on the femtosecond scale examples of the latter. The purpose of this book is to examine the realm of phenomena of such extreme type and the techniques that permit their investigations. Each author has developed a coherent section of the program starting at a somewhat fundamental level and ultimately reaching the frontier of knowledge in the field in a systematic and didactic fashion. The formal lectures are complemented by additional seminars.

This two-volume work covers ultrafast structural and electronic dynamics of elementary processes at solid surfaces and interfaces, presenting the current status of photoinduced processes. Providing valuable introductory information for newcomers to this booming field of research, it investigates concepts and experiments, femtosecond and attosecond time-resolved methods, as well as frequency domain techniques. The whole is rounded off by a look at future developments.

The many-body-theoretical basis and applications of theoretical spectroscopy of condensed matter, e.g. crystals, nanosystems, and molecules are unified in one advanced text for readers from graduate students to active researchers in the field. The theory is developed from first principles including fully the electron-electron interaction and spin interactions. It is based on the many-body perturbation theory, a quantum-field-theoretical description, and Green's functions. The important expressions for ground states as well as electronic single-particle and pair excitations are explained. Based on single-particle and two-particle Green's functions, the Dyson and Bethe-Salpeter equations are derived. They are applied to calculate spectral and response functions. Important spectra are those which can be measured using photoemission/inverse photoemission, optical spectroscopy, and electron energy loss/inelastic X-ray spectroscopy. Important approximations are derived and discussed in the light of selected computational and experimental results. Some numerical implementations available in well-known computer codes are critically discussed. The book is divided into four parts: (i) In the first part the many-electron systems are described in the framework of the quantum-field theory. The electron spin and the spin-orbit interaction are taken into account. Sum rules are derived. (ii) The second part is mainly related to the ground state of electronic systems. The total energy is treated within the density functional theory. The most important approximations for exchange and correlation are delighted. (iii) The third part is essentially devoted to the description of charged electronic excitations such as electrons and holes. Central approximations as Hedin's GW and the T-matrix approximation are discussed.(iv) The fourth part is focused on response functions measured in optical and loss spectroscopies and neutral pair or collective excitations.

Based on a NATO Advanced Summer Institute, this volume discusses physical models, mathematical formalisms, experimental techniques, and applications for ultrafast dynamics of quantum systems. These systems are used in laser optics, spectroscopy, and utilize monochromaticity, spectral brightness, coherence, power density, and tunability of laser sources.