Optical Generation And Control Of Quantum Coherence In Semiconductor Nanostructures

The fundamental concept of quantum coherence plays a central role in quantum physics, cutting across disciplines of quantum optics, atomic and condensed matter physics. Quantum coherence represents a universal property of the quantum s- tems that applies both to light and matter thereby tying together materials and p- nomena. Moreover, the optical coherence can be transferred to the medium through the light-matter interactions. Since the early days of quantum mechanics there has been a desire to control dynamics of quantum systems. The generation and c- trol of quantum coherence in matter by optical means, in particular, represents a viable way to achieve this longstanding goal and semiconductor nanostructures are the most promising candidates for controllable quantum systems. Optical generation and control of coherent light-matter states in semiconductor quantum nanostructures is precisely the scope of the present book. Recently, there has been a great deal of interest in the subject of quantum coh- ence. We are currently witnessing parallel growth of activities in different physical systems that are all built around the central concept of manipulation of quantum coherence. The burgeoning activities in solid-state systems, and semiconductors in particular, have been strongly driven by the unprecedented control of coherence that previously has been demonstrated in quantum optics of atoms and molecules, and is now taking advantage of the remarkable advances in semiconductor fabrication technologies. A recent impetus to exploit the coherent quantum phenomena comes from the emergence of the quantum information paradigm.

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.

Nano-Enabled Agrochemicals in Agriculture presents a targeted overview of the safe implementation of nanotechnologies within agricultural and horticultural settings, with the purpose of achieving enhanced production while maintaining ecological integrity. The growing global request for agricultural crops and products requires high standards of quality and safety, which has stimulated the search for new technologies that preserve their quality and delay their decomposition. Nanotechnology may boost plant production by improving nutrient uptake/use efficiency with nanoformulations of fertilizers and agrochemicals for plant enhancement, detection and treatment of diseases, and host-parasite interactions at the molecular level using nanosensors. It also may improve plant disease diagnostics, removal of contaminants from soil and water, postharvest management of vegetables and flowers, and reclamation of salt-affected soils. Although the markets for nanoproducts and nanoformulations continue to increase, there are also growing concerns regarding the fate and behavior of nanomaterials in environmental systems. Exploring important topics related to nanotechnology and nanomaterials, the book includes the use of nanochemicals in insect pest management, as nanofungicides, nanoherbicides, micronutrient supply, and nanosensors to monitor crop and soil health conditions, from detection of agrochemicals to their slow release of agrochemicals, and their impact on related environs. This book will serve as an excellent resource for a wide range of plant scientists who have concerns about nanomaterial interactions with terrestrial and aquatic plants. Focuses on emerging important topics related to nanotechnology and nanomaterials on agricultural systems Emphasizes new applications of nanomaterials in the agricultural sciences, from fertilizers to irrigation systems Addresses concerns about nanomaterial interactions with terrestrial and aquatic plants

This book offers an extensive introduction to the extremely rich and intriguing field of spin-related phenomena in semiconductors. In this second edition, all chapters have been updated to include the latest experimental and theoretical research. Furthermore, it covers the entire field: bulk semiconductors, two-dimensional semiconductor structures, quantum dots, optical and electric effects, spin-related effects, electron-nuclei spin interactions, Spin Hall effect, spin torques, etc. Thanks to its self-contained style, the book is ideally suited for graduate students and researchers new to the field.

Covering general theoretical concepts and the research to date, this book demonstrates that Bose-Einstein condensation is a truly universal phenomenon.

This textbook presents basic and advanced computational physics in a very didactic style. It contains very-well-presented and simple mathematical descriptions of many of the most important algorithms used in computational physics. The first part of the book discusses the basic numerical methods. The second part concentrates on simulation of classical and quantum systems. Several classes of integration methods are discussed including not only the standard Euler and Runge Kutta method but also multi-step methods and the class of Verlet methods, which is introduced by studying the motion in Liouville space. A general chapter on the numerical treatment of differential equations provides methods of finite differences, finite volumes, finite elements and boundary elements together with spectral methods and weighted residual based methods. The book gives simple but non trivial examples from a broad range of physical topics trying to give the reader insight into not only the numerical treatment but also simulated problems. Different methods are compared with regard to their stability and efficiency. The exercises in the book are realised as computer experiments.

Understanding the coherent dynamics of electron spins in quantum dots (QDs) is important for potential applications in solid-state, spin-based electronics and quantum information processing. Here, results are presented focusing on optical initialization, manipulation, and readout of spin coherence in various semiconductor nanostructures. Layered semiconductor nanocrystals are fabricated containing a spherical "quantum shell" in which electrons and holes are confined. As in a planar quantum well, the quantized energy levels and g-factors are found to depend on the shell thickness. Taking this idea a step further, nanocrystals with a concentric, tunnel-coupled core and shell are investigated. Based on the energy and g-factor dependences in these structures, spins can be selectively initialized into, and read out from, states in the core and shell. In contrast to these two ensemble measurements, we next turn to measurements of single electron spins in single QDs. First, we demonstrate the detection of a single electron spin in a QD using a nondestructive, continuously averaged magneto-optical Kerr rotation (KR) measurement. This continuous single QD KR technique is then extended into the time domain using pulsed pump and probe lasers, allowing the observation of the coherent evolution of an electron spin state with nanosecond temporal resolution. By sweeping the delay between the pump and probe, the dynamics of the spin in the QD are mapped out in time, providing a direct measurement of the electron g-factor and spin lifetime. Finally, this time-resolved single spin measurement is used to observe ultrafast coherent manipulation of the spin in the QD using an off-resonant optical pulse. Via the optical Stark effect, this optical pulse coherently rotates the spin state through angles up to pi radians, on picosecond timescales.

Semiconductor nanostructures are attracting a great deal of interest as the most promising device with which to implement quantum information processing and quantum computing. This book surveys the present status of nanofabrication techniques, near field spectroscopy and microscopy to assist the fabricated nanostructures. It will be essential reading for academic and industrial researchers in pure and applied physics, optics, semiconductors and microelectronics. The first up-to-date review articles on various aspects on quantum coherence, correlation and decoherence in semiconductor nanostructures