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.

The advent of the femto-second laser has enabled us to observe phenomena at the atomic timescale. One area to reap enormous benefits from this ability is ultrafast dynamics. Collecting the works of leading experts from around the globe, Non-Equilibrium Dynamics of Semiconductors and Nanostructures surveys recent developments in a variety of areas in ultrafast dynamics. In eight authoritative chapters illustrated by more than 150 figures, this book spans a broad range of new techniques and advances. It begins with a review of spin dynamics in a high-mobility two-dimensional electron gas, followed by the generation, propagation, and nonlinear properties of high-amplitude, ultrashort strain solitons in solids. The discussion then turns to nonlinear optical properties of nanoscale artificial dielectrics, optical properties of GaN self-assembled quantum dots, and optical studies of carrier dynamics and non-equilibrium optical phonons in nitride-based semiconductors. Rounding out the presentation, the book examines ultrafast non-equilibrium electron dynamics in metal nanoparticles, monochromatic acoustic phonons in GaAs, and electromagnetically induced transparency in semiconductor quantum wells. With its pedagogical approach and practical, up-to-date coverage, Non-Equilibrium Dynamics of Semiconductors and Nanostructures allows you to easily put the material into practice, whether you are a seasoned researcher or new to the field.

The interaction of time-dependent electromagnetic fields with electrons in quantum materials can give rise to many both fundamentally interesting as well as technologically relevant phenomena like transient band structure manipulations or the emergence of prethermal states of matter, which are not a result of heating. This thesis contributes theoretical insights to both these topics: We model the interference of Floquet and Volkov side bands, which are a result of the dressing of electron states by light, in a time-resolved angle-resolved photoemission spectroscopy (ARPES) experiment. Furth...

This book presents the first comprehensive treatment of discrete phase-space quantum mechanics and the lattice Weyl-Wigner formulation of energy band dynamics, by the originator of these theoretical techniques. The author's quantum superfield theoretical formulation of nonequilibrium quantum physics is given in real time, without the awkward use of artificial time contour employed in previous formulations. These two main quantum theoretical techniques combine to yield general (including quasiparticle-pairing dynamics) and exact quantum transport equations in phase-space, appropriate for nanodevices. The derivation of transport formulas in mesoscopic physics from the general quantum transport equations is also treated. Pioneering nanodevices are discussed in the light of the quantum-transport physics equations, and an in-depth treatment of the physics of resonant tunneling devices is given. Operator Hilbert-space methods and quantum tomography are discussed. Discrete phase-space quantum mechanics on finite fields is treated for completeness and by virtue of its relevance to quantum computing. The phenomenological treatment of evolution superoperator and measurements is given to help clarify the general quantum transport theory. Quantum computing and information theory is covered to demonstrate the foundational aspects of discrete quantum dynamics, particularly in deriving a complete set of multiparticle entangled basis states.

Excited-state dynamics simulation enables us to explore a wide variety of nonequilibrium phenomena remaining uncharted in the field of physics, (bio)chemistry, and materials science. To elucidate electron-enhanced atomic-layer deposition, we simulate inelastic electron scattering followed by nonadiabatic molecular dynamics using time-dependent density functional theory (TDDFT) along with Ehrenfest dynamics. Also, photodegradation of hybrid perovskite solar cells is studied in terms of quantum chaos of the molecular cation using TDDFT. Quantum transport emerges when the wave nature of matter plays a role. We utilize the nonequilibrium Green0́9s function formalism (NEGF) formalism to study coherent/incoherent quantum transport and localization in disordered systems, e.g., amorphous semiconductors and amorphous/crystalline hetero-phase materials. Quantum information science has the potential for solving problems that no one can ever solve in classical technology. We are devoted to understanding and predicting materials properties relevant to the performance of solid-state qubits. From this perspective, we study edge-contact effects on the transparency of graphene Josephson junctions for topological superconductivity. The dissertation demonstrates a wide range of applications, where excited-state dynamics and quantum transport emerge, and exhibits the potential of the rather unconventional but advanced computational approaches in the field of materials research.

The four-week period fran May 20 to June 16, 1984 was an intensive period of advanced study on the foundations and frontiers of nonequili brium statistical physics (NSP). During the first two weeks of this period, an advanced-study course on the "Foundations of NSP" was con ducted in Albuquerque under the sponsorship of the University of New Mexico Center for High-Technology Materials. This was followed by a two-week NATO Advanced Study Insti tute on the "Frontiers of NSP" in Santa Fe under the same directorship. Many Students attended both meetings. This book comprises proceedings based on those lectures and covering a broad spectrum of topics in NSP ranging fran basic problems in quantum measurement theory to analogies between lasers and Darwinian evolution. The various types of quantum distribution functions and their uses are treated by several authors. other tools of NSP, such as Langevin equations, Fokker-Planck equations, and master equations, are developed and applied to areas such as laser physics, plasma physics, Brownian motion, and hydrodynamic instabilities. The properties and experimental detection of squeezed states and antibunching are described, as well as experimental tests of the violation of Bell's inequality. Information theory, mean-field theory, reservoir theory, entropy maximization, and even a novel nonlinear generalization of quantum mechanics are used to discuss nonequilibrium phenanena and the approach toward thermodynamic equilibrium.