In Transport in Phonon Systems'' the principles of physical kinetics are given and the description of transport properties in a wide class of macroscopic physical systems - the phonon systems - is presented. Important problems of phonon transport such as thermal conductivity and thermal waves of second sound, dielectric losses, sound propagation and absorption, phonon echo, and phonon transport in superfluid helium II are discussed. Many of these problems are discussed for the first time and the author presents numerous original results. Not only specialists but also those wishing to enter the field of phonon physics and phonon kinetics can benefit from Transport in Phonon Systems''.
Over the last two decades, advanced fabrication techniques have enabled the fabrication of materials and devices at sub-micron length scales. For heat conduction, the conventional Fourier model for predicting energy transport has been shown to yield erroneous results on such length scales. In semiconductors and dielectrics, energy transport occurs through phonons, which are quanta of lattice vibrations. When phase coherence effects can be ignored, phonon transport may be modeled using the semi-classical phonon Boltzmann transport equation (BTE). The objective of this thesis is to develop an efficient computational method to solve the BTE, both for single-material and multi-material systems, where transport across heterogeneous interfaces is expected to play a critical role. The resulting solver will find application in the design of microelectronic circuits and thermoelectric devices. The primary source of computational difficulties in solving the phonon BTE lies in the scattering term, which redistributes phonon energies in wave-vector space. In its complete form, the scattering term is non-linear, and is non-zero only when energy and momentum conservation rules are satisfied. To reduce complexity, scattering interactions are often approximated by the single mode relaxation time (SMRT) approximation, which couples different phonon groups to each other through a thermal bath at the equilibrium temperature. The most common methods for solving the BTE in the SMRT approximation employ sequential solution techniques which solve for the spatial distribution of the phonon energy of each phonon group one after another. Coupling between phonons is treated explicitly and updated after all phonon groups have been solved individually. When the domain length is small compared to the phonon mean free path, corresponding to a high Knudsen number ([mathematical equation]), this sequential procedure works well. At low Knudsen number, however, this procedure suffers long convergence times because the coupling between phonon groups is very strong for an explicit treatment of coupling to suffice. In problems of practical interest, such as silicon-based microelectronics, for example, phonon groups have a very large spread in mean free paths, resulting in a combination of high and low Knudsen number; in these problems, it is virtually impossible to obtain solutions using sequential solution techniques. In this thesis, a new computational procedure for solving the non-gray phonon BTE under the SMRT approximation is developed. This procedure, called the coupled ordinates method (COMET), is shown to achieve significant solution acceleration over the sequential solution technique for a wide range of Knudsen numbers. Its success lies in treating phonon-phonon coupling implicitly through a direct solution of all equations in wave vector space at a particular spatial location. To increase coupling in the spatial domain, this procedure is embedded as a relaxation sweep in a geometric multigrid. Due to the heavy computational load at each spatial location, COMET exhibits excellent scaling on parallel platforms using domain decomposition. On serial platforms, COMET is shown to achieve accelerations of 60 times over the sequential procedure for Kn
This book brings together leading names in the field of nanoscale energy transport to provide a comprehensive and insightful review of this developing topic. The text covers new developments in the scientific basis and the practical relevance of nanoscale energy transport, highlighting the emerging effects at the nanoscale that qualitatively differ from those at the macroscopic scale. Throughout the book, microscopic energy carriers are discussed, including photons, electrons and magnons. State-of-the-art computational and experimental nanoscale energy transport methods are reviewed, and a broad range of materials system topics are considered, from interfaces and molecular junctions to nanostructured bulk materials. Nanoscale Energy Transport is a valuable reference for researchers in physics, materials, mechanical and electrical engineering, and it provides an excellent resource for graduate students.
In recent years there has been a huge increase in the research and development of nanoscale science and technology. Central to the understanding of the properties of nanoscale structures is the modeling of electronic conduction through these systems. This graduate textbook provides an in-depth description of the transport phenomena relevant to systems of nanoscale dimensions. In this textbook the different theoretical approaches are critically discussed, with emphasis on their basic assumptions and approximations. The book also covers information content in the measurement of currents, the role of initial conditions in establishing a steady state, and the modern use of density-functional theory. Topics are introduced by simple physical arguments, with particular attention to the non-equilibrium statistical nature of electrical conduction, and followed by a detailed formal derivation. This textbook is ideal for graduate students in physics, chemistry, and electrical engineering.
This book develops a methodology for the real-time coupled quantum dynamics of electrons and phonons in nanostructures, both isolated structures and those open to an environment. It then applies this technique to both fundamental and practical problems that are relevant, in particular, to nanodevice physics, laser–matter interaction, and radiation damage in living tissue. The interaction between electrons and atomic vibrations (phonons) is an example of how a process at the heart of quantum dynamics can impact our everyday lives. This is e.g. how electrical current generates heat, making your toaster work. It is also a key process behind many crucial problems down to the atomic and molecular scale, such as the functionality of nanoscale electronic devices, the relaxation of photo-excited systems, the energetics of systems under irradiation, and thermoelectric effects. Electron–phonon interactions represent a difficult many-body problem. Fairly standard techniques are available for tackling cases in which one of the two subsystems can be treated as a steady-state bath for the other, but determining the simultaneous coupled dynamics of the two poses a real challenge. This book tackles precisely this problem.
The monograph is devoted to the investigation of physical processes that govern the phonon transport in bulk and nanoscale single-crystal samples of cubic symmetry. Special emphasis is given to the study of phonon focusing in cubic crystals and its influence on the boundary scattering and lattice thermal conductivity of bulk materials and nanostructures.
