bluuebunny/crossref_metadata_2025_split huggingface dataset:
The two-dimensional electron gas
Authors: Kelly M J 
Published: November 2023

Abstract
In this chapter, we describe the two main systems that have driven research into low-dimensional physics over the last two decades. The metal-oxide-semiconductor field-effect transistor (MOSFET) was patented over 50 years ago, but the technology of oxidizing a Si surface in a way that left few remaining unsatisfied bonds (which have undesirable electrical activity) was perfected only in the 1960s, just in time for its exploitation in modern integrated circuitry where it has been the key active device (Nicollian and Brews 1982). High electron mobilities in GaAs-AlGaAs multilayers with selective doped layers were discovered in 1978 (Dingle et al. 1978), and this selective doping principle has become incorporated into the high-electronmobility transistor (HEMT), at present the lowest noise transistor available, and used in amplifying weak signals, with the particular domestic application of receiving television signals from space. The commercial success of these two structures has increased the levels of research investment in multilayer structures more generally. In both structures, we have electrons that are ‘trapped’ at an interface, but are free to move (with metallic-like conduction properties) along the interface. The physics of these electron systems has been of wide interest, while attempts to improve the performance of these structures as devices have led to many of the new materials and device technologies that we now take for granted. Historically, the Si-Si02 system dominated research in the 1970s (Ando et al. 1982), while the GaAs-AlGaAs heterojunction dominated research in the 1980s. Although most of this book is about III-V epitaxial multilayers, experience with the Si MOSFET set the scene for much of the research that followed.
Quantum pillars and boxes: electronic and optical properties
Authors: Kelly M J 
Published: November 2023

Abstract
New physics associated with hot electron injection, tunnelling, and quantum confinement is made possible with hetero junctions in multilayer semiconductor structures. The new physics has been successfully applied to devices, where the hetero junctions ensure that the active volume is Q2D (as in FETs and quantum-well lasers). Even the tunnel structures are very thin in one of the three spatial dimensions. Given the proven advantages in going from bulk to Q2D systems, a further reduction in dimensionality might again lead to new and exploitable physics in semiconductors. We describe the new physics in this chapter and comment on its exploitability. We concentrate on the fabrication of structures that are on the quantum-length scale of c.20 nm in two, or all three, spatial dimensions, giving quantum wires (pillars) and quantum dots (boxes) respectively. We concentrate on the electrical and optical properties of the former and the optical properties of the latter. In practice, we encounter some new effects associated with the intrinsically small size of the structures (i.e. containing only a few carriers), but we leave the general physics of such mesoscopic systems to the following chapter. In addition, the finite charge of an electron plays a role in the energetics of small structures, and effects associated with this are also treated in Chapter 12.
Exotic materials combinations: new physics including strain
Authors: Kelly M J 
Published: November 2023

Abstract
So far, we have considered the physics of the GaAs-AlxGa1-x As system. The alloy semiconductor is direct gap for Al contents below 45 per cent, and the effective mass approximation gives a satisfactory (semi-quantitative) account of all the important optical and electronic properties of multilayers and microstructures. For more than 45 per cent Al, the wider-gap material is indirect gap and some further care must be taken with the detailed matching of wave functions at the interfaces if quantitative results are sought. The GaAs-AIGaAs materials system is the most mature, as the lattice constant varies by less than 0.2 per cent across the entire composition range. Furthermore, the thermal expansion of the alloy and GaAs are the same, so that no further stresses are introduced as the material is cooled to room temperature and further to cryogenic temperatures from typical multilayer growth temperatures of about 580-600 °C. Even within this fairly straightforward system, the precise offset of the conduction and valence bands at the abrupt heterojunction has been a matter of continuing debate. It is now thought that a conduction band to valence band offset ratio of 65 ±5 per cent to 35 ±5 per cent is appropriate for describing the physics of the hetero junctions. However, abrupt doping profiles similar those of the planar doped barrier described in Chapter 2, Section 2.6, can introduce (deliberately or unintentionally) a dipole layer at a heterojunction, and so move the two band structures with respect to each other in energy (Shen et al. 1992).
Amorphous semiconductor multilayers
Authors: Kelly M J 
Published: November 2023

Abstract
So far, all the materials physics and devices have used single-crystal multilayer semiconductor structures. Great effort has been made in the growth to achieve precise single-crystal properties and sharp interfaces between adjacent layers. During the fabrication of devices, the process steps attempt to preserve the crystalline integrity. In the past 20 years, hydrogenated amorphous Si has developed rapidly from a research material (first doped to make p-n junction devices in 1976) to the host material for the electronics of displays, with a $4 billion turnover in 1991-1992 (Le Comber 1992). It is now possible to obtain photocells for powering calculators, watches, etc., photoconductors for a wide range of sensing applications, thin-film transistors for driving liquid-crystal displays, and high-voltage thin-film transistors for driving printers. The films of amorphous Si suitable for devices are prepared by plasma-enhanced chemical vapour deposition from SiH4. In the early days, the role of hydrogen was underestimated in this device-grade material, but it is now known to constitute anywhere in the 2-16 at. % range (Street 1991) (this reference is a comprehensive introduction to hydrogenated amorphous Si, including an introduction to multilayers). The role of hydrogen is to saturate all the unsatisfied dangling bonds in a continuous random network. Studies of ideal random networks (shown schematically in Fig. 20.1) indicate that a dangling bond is electronically active with energy levels in and near the gap. The formation of Si-H bonds saturates these bonds and moves the relevant states far from the gap. Only states associated with unsatisfied Si-H bonds and with traditional donors and acceptors remain in the gap, and the behaviour of the latter is similar to that in crystalline semiconductors. The nearest-neighbour distance between Si atoms is the same as in the crystal, and the density of amorphous Si is only a few per cent less than that of single-crystal Si. There is some evidence that the Si-H bonds are metastable, and that movement of hydrogen takes place between different bonds (Street 1991). The electronic structure of an amorphous semiconductor differs from its crystalline counterpart; despite the absence of long-range order, and a band structure in the conventional sense, there is still a principal bandgap. The band-edge densities of states do not have the sharp E energy dependence, but rather an exponential tail brought about by electron states localized in regions of lower potential energy within the amorphous network; these states are spread over a range with an energy scale E0 ∼ 0.1 eV associated with it (Fig. 20.l(b)).
The theory of light scattering from rod-like polyelectrolytes
Authors: Odijk Theo 
Published: November 2023

Abstract
A significant class of polyelectrolytes consists of slender, rod-like particles. Important examples include biopolymers such as short double-stranded DNA, helical xanthan, schizophyllan, F-actin, tobacco mosaic virus and fd virus. They may be semi-flexible but if the ratio of the persistence length to the contour length is smaller than unity, it becomes useful to model the polyions by charged rods. Inorganic colloids such as vanadium pentoxide and boehmite form another interesting subclass which may be considered completely rigid rods for most practical purposes. My objective here is to present a virial theory for the scattering by semi-dilute and concentrated isotropic solutions of rod-like polyelectrolytes, albeit under excess salt conditions.
Scattering fron1 concentrated polymer solutions
Authors: Nicolai Taco , Brown Wyn 
Published: November 2023

Abstract
Following the development of scaling theories by de Gennes and coworkers, a main focus of interest in polymer-solvent systems has been the so-called semi-dilute regime. Semi-dilute solutions are those having a very low polymer volume fraction and at the same time a strong overlap of the polymer coils.
Scattering properties of ternary polymer solutions
Authors: Borsali Redouane 
Published: November 2023

Abstract
To achieve a better understanding of polymer mixture properties, considerable effort has been made, over the past decade, on the static and the dynamic behaviours both in solution and in the bulk, from theoretical and experimental points of view. The aim of this chapter is to discuss the scattering properties of these systems on the basis of recent developments and to emphasize how one extracts important parameters such as the mobility of the chains (diffusion process) and the interaction parameter (compatibility) which control the dynamics and the thermodynamics. Using linear response theory and the random phase approximation (RPA), it has been shown that two relaxation modes describe the dynamic behaviour of incompressible polymer/polymer/ solvent systems. The first mode characterizes the total polymer concentration fluctuations and reflects the collective motion of all the polymer chains with respect to the solvent (excluded volume effect).
Light scattering in complex micellar systems
Authors: Schurtenberger Peter 
Published: November 2023

Abstract
Surfactants in solution exhibit a complex aggregation behaviour as a result of a delicate balance of opposing forces. Micellar solutions and microemulsions represent thermodynamically stable liquid dispersions containing surfactant aggregates, which can often be found in a large region of the phase diagram of two-or multi-component surfactant systemsP-In micellar dispersions, the aggregates are formed by self-assembly of surfactant monomers. While micelles are frequently spherical, they can also exhibit a sphere-to-rod transition and even grow to giant flexible and polymer-like aggregates. This micellar growth can be induced by a reduction in the so-called spontaneous curvature H0due to a change in a ‘control parameter’ such as temperature (in non-ionic surfactant systems), ionic strength (in ionic surfactant systems) or cosurfactant concentration, which subsequently results in a characteristic transition in the particle morphology from spheres to cylinders to lamellae.
Light scattering by block copolymer liquids in the disordered and ordered state
Authors: Štěpanek Petr , Lodge Timothy P 
Published: November 2023

Abstract
Block copolymers form a very important class of materials and are attracting increased attention because of their unique and widely variable properties. Block copolymers are macromolecules built of sequences of distinct repeat units. The number and chemical nature of the blocks can be varied but, most frequently, only two blocks, A and B, or three blocks A, B and C, are utilized. These can be used to generate a variety of chain architectures of which the most common types, both in laboratory experiments and in industrial applications, are AB diblock or ABA triblock copolymers. Less frequently, block copolymers of type ABC or (A–B)n are utilized.
Size distributions from static light scattering
Authors: Hallett F Ross 
Published: November 2023

Abstract
A knowledge of particle size distributions is central to innumerable scientific and applied problems in analytical chemistry, chemical physics and biophysics, atmospheric sciences and a host of other disciplines. A wide variety of techniques has been used to measure particle sizes These include dynamic light scattering (DLS), static light scattering (SLS), turbidimetry, small angle diffraction, optical particle counting, velocimetry, small angle X-ray and neutron scattering, size exclusion chromatography, electron microscopy, sedimentation and sieving/filtering. No one technique is suited for all particles and all conditions.
Quark Bilinear Operators
Authors: Ripka Georges 
Published: November 2023

Abstract
Meson fields couple directly to bilinear operators which carry the same quantum numbers. They can be introduced into quark actions so as to linearize products of quark bilinears (section 4.3). In some cases, it is useful to eliminate completely the quark field from the effective action, in favor of the meson fields. So-called bosonized forms of effective actions are obtained this way.
Static applications
Authors: Leupold H A 
Published: November 2023

Abstract
The advent of rare-earth permanent magnets (REPM) has brought about magnetic structures that were previously impracticable [Rot78, Tau85]. So different are these remakable materials from the earlier magnets that conventional design wisdom is inadequate to fully exploit their unique characteristics. Indeed, the conventional approach can lead to error or to the employment of quite inappropriate design procedures. The salutary characteristics stem from two basic attributes of the earth materials: (i) large intrinsic moments per unit volume; (ii) extraordinarily high resistance to demagnetization by external or internal demagnetizing fields.
Light energy
Authors: Akhmanov S A , Nikitin S YU 
Published: November 2023

Abstract
The energy flux carried by an optical wave. Optical beams and pulses: energy, power, and intensity. The spatial and temporal compression of light energy. Basic concepts of photometry. The capability to carry energy is one of the fundamental properties of light. The notion of electromagnetic energy is shown to emerge from Maxwell theory. The possibilities for spatial and temporal compression of optical energy are discussed and numerical estimates given.
Emission from an oscillator ensemble
Authors: Akhmanov S A , Nikitin S YU 
Published: November 2023

Abstract
From the dynamics of an oscillator to the statistics of an ensemble. Non-laser sources of light: intensity, polarization, and radiation directivity pattern. Radiation statistics of independent oscillators. The radiation spectrum. Mechanisms of spectral line broadening. Natural broadening. Doppler broadening. Collision-induced broadening and the shift of a spectral line. Dicke’s effect: collision-induced narrowing of a Doppler spectral line in a dense gas.
A linear oscillator in an optical field
Authors: Akhmanov S A , Nikitin S YU 
Published: November 2023

Abstract
Absorption of light by an oscillator and by an oscillator ensemble. The Bouguer law. Absorption spectroscopy. Decrease in the phase velocity of light propagating in a medium and the index of refraction. An inhomogeneous ensemble of oscillators. Homogeneous and inhomogeneous widths of spectra. Excitation by a short pulse-energy relaxation and dephasing. Principles of frequency- and time-domain spectroscopy.
Non-equilibrium Simulations of the Ising model
Authors: Newman M E J , Barkema G T 
Published: November 2023

Abstract
As our first example of the ideas introduced in Chapter 9 we now look at how the using model comes to equilibrium. As well as being a simple demonstration of most of the important ideas of out-of-equilibrium Monte Carlo simulation, our studies of the using model also tell us about real physics. As we explain in the next section, the equilibration of the using model below its equilibrium phase transition temperature sheds light on the physical phenomenon known as “spinodal decomposition”.
Random Numbers
Authors: Newman M E J , Barkema G T 
Published: November 2023

Abstract
The fundamental constant which links all Monte Carlo methods together, the common factor which makes them all Monte Carlo methods, is that they contain an element of randomness. Things happen in a probabilistic fashion in a Monte Carlo calculation, and it is only the average over many unpredictable events that gives us an (approximate) answer to the question we are interested in. To generate such unpredictable events, all Monte Carlo methods require a source of random numbers. There are many ways of generating random numbers. In this chapter we examine some of the most common of them.
Nonlinear Magneto-Optical Studies of Ultrathin Films and Multila Yers
Authors: Rasing Th. 
Published: November 2023

Abstract
The strong activity and success in magnetic thin-film research is based on the current developments in surface and material science, enabling the manipulation and control of thin-film structures on the atomic level and the parallel development of many spin-appended derivations of surface science tcchnigues.1 Some of the most exciting recent discoveries, like the giant magnetoresistance (GMR) and the oscillatory exchange coupling, are related to the properties of multilayers of alternating ferromagnetic and paramagnetic layers. As the inter face between these layers appear to play an essential role for these phenomena and consequently for the device properties based on them, a detailed study of the magnetic interface properties is needed.
Theory for Nonlinear Optics at Interfaces and in Thin Films of Metals: Selected Problems
Authors: Luce T A , Bcnnemann K H 
Published: November 2023

Abstract
We focus here on some important problems to supplement and extend the theory outlined by Hiihner, to demonstrate the potential of nonlinear optics regarding the analysis of the electronic and magnetic structure of interfaces and thin films, and to sketch some interesting problems to be solved. First, we summarize the most important general properties of second harmonic generation (SHG) from metals. Then, we discuss some problems reflecting the inter play of effects due to the optical transition matrix elements and the electronic energy spectrum availahlc for these transitions.
Introduction
Authors: Ejiri H , Toki H 
Published: November 2023

Abstract
The nuclear physics of nucleon-hadron many-body systems is concerned with fundamental structures of interacting nuclear particle systems. Here, nuclear particles are particles involved in nucleon/hadron systems and interactions therein. The particles to be considered are primarily quarks in the case of hadrons, and are mostly hadrons in the case of nuclei. Nuclear interactions associated with them are strong, weak, and electromagnetic ones. They are given by gauge fields with relevant gauge bosons. Then the gauge bosons to be considered in quark-lepton systems are gluons, weak bosons, and photons. Leptons are necessarily involved in nuclear weak processes. Gravitational interactions are significant only in special cases in astrophysics, such as neutron stars and supernovae. In the case of nucleon-hadron systems, meson exchange interactions and effective nucleon interactions are used in place of the QCD gluon field due to confinement of quarks and spontaneous chiral symmetry breaking.
Spin—isospin giant resonances by charge-exchange reactions
Authors: Fujiwara Mamoru 
Published: November 2023

Abstract
A nucleus primarily consists of protons and neutrons. This microscopic world is governed by a strong force, i.e. the nuclear interaction mediated by the exchange of pions and other heavy mesons between the nucleons. If the interactions between the constituents in a nucleus are known, the behaviour of this microscopic world can, in principle, be described. But, the actual situation is not so simple since the many-body problem can be solved exactly only for two- and three-body systems with some basic physical assumptions. Thus, all theoretical analyses of nuclei need a model, the validity of which should be checked by experimental tests in order to confirm the underlying approximations or to improve them.
Breakup processes and cluster structures of light composite projectiles
Authors: Sakuragi Y 
Published: November 2023

Abstract
In nuclear reactions induced by light composite projectiles, many of which are loosely bound systems, projectile breakup takes place strongly as a real or a virtual process and is known to play an important role in various nuclear reactions. In this chapter, we review the present status of our understanding of reaction mechanisms relevant to the nuclear breakup processes and their role in nuclear reactions induced by light composite projectiles.
Physics of snowballs—impurity ions in superfluid helium
Authors: Takahashi N , Shimoda T 
Published: November 2023

Abstract
The strange behaviour of liquid helium has been attracting the attention of quite a number of physicists ever since helium was liquified and is still doing so after almost a century. It may well not be an exaggeration to say that new precise measurements of physical quantities concerning liquid helium succeed in reviving discussions about our physical insights into the problems of liquid helium.
Atomic physics with cyclotron beams
Authors: Katayama lchiro 
Published: November 2023

Abstract
Why atomic physics at a cyclotron laboratory? ‘The interaction is very clear, so what is left for study?’ —this is often what I was asked when we started atomic collision studies at RCNP. I hope this report provides some answers to the question. Firstly, I would like to remark on the so-called ‘Massey criterion’, which states that between a projectile and an electron, in a certain orbit in a target atom, the strongest interaction is expected when the velocities match each other. As the velocity of a K-shell electron in Pb atom equals that of a 160 MeV proton, this implies that, in order to study the excitation of inner-shell electrons in heavy atoms, one needs very high energy ion beams. Secondly, there is one other aspect, viz. the potential usage of a foil target. All the atomic physics experiments which were done at RCNP utilized thin foils, even though some of them aimed to study a single collision process, e.g. electron capture and loss process. Others were designed to study solid state effects such as channelling, convoy electrons, stopping-power experiments, and so on. (Although they are not topics from pure atomic physics in a strict sense, we include them in this review.) Even for these solid state effect experiments, the use of high energy beams from cyclotron is more effective, since it relaxes us from ultra-high vacuum condition. There is another advantage in studying atomic collisions at RCNP: one can use the high-resolution magnetic spectrograph RAIDEN, which is quite unique if one compares it with facilities available at other institutes.
Nuclear physics with strange flavour
Authors: Kishimoto Tadafumi , Motoba Toshio 
Published: November 2023

Abstract
It is well known that quarks are real constituents of hadrons. The interactions among quarks are described by Quantum ChromoDynamics (QCD), where the interaction between three colour charges is mediated by gluons. Nuclei are made up of nucleons held by the strong interaction, though it has been quite rare to require explicit quark degrees of freedom to understand many aspects of their low-energy phenomena. Since hadrons are colour singlets, the interactions among nucleons are the residual interactions of quarks, which is responsible for the success of the meson theory.