Abstract Considers solutions of the Schrödinger wave equation for a single electron confined in the potential distribution associated with the hydrogen atom. Finds spherically-symmetric solutions, together with their associated energy levels and probability distributions. Introduces the idea of quantum numbers to describe more general non-symmetric states. Considers the additional effect of electron spin, and introduces Pauli’s exclusion principle as the limit to the number of electrons in any given state. Discusses how the periodic table of the elements can follow from solutions of the Schrödinger equation for atoms with larger numbers of electrons.

Abstract Introduces the Schrödinger wave equation as the key equation governing the behaviour of electrons, and presents simple solutions (known as wave functions) as electron waves, and packets of electron waves, which can represent localised, particle-like electrons. Considers the behaviour of electron waves on meeting a potential barrier and trapped in potential wells with finite and infinite walls, and introduces the idea of energy levels. Discusses the accepted interpretation of the electron wave function, namely that its modulus square leads to the probability of finding an electron in a given region of space. Considers further the uncertainty relationship and associated philosophical implications.

Abstract Introduces the idea of free electrons in a metal as solutions of the Schrödinger equation for the potential distribution defining a large, three-dimensional volume, finds the associated density of states, shows that the probability of occupation of those states is given by the Fermi-Dirac distribution function, and uses these ideas to define the specific heat of electrons. Introduces the work function as the energy needed for an electron to escape from a metal, and shows how a supply of thermal energy can increase emission in the heated tungsten filament. Shows further how strong electric fields can reshape the confining potential barrier (the Schottky effect), allowing escape by tunneling and enabling the field emission microscope. Shows how the energy may alternatively be provided by photons in the photoelectric effect. Finally, considers a related application for tungsten filament, the tungsten-halogen lamp, and electron behaviour at a junction between two metals.

The macroscopic and microscopic approaches to determining polarization are explained. The types of polarization, frequency response, and anomalous dispersion are discussed. The Debye equation for orientational polarization is derived. The concept of effective field is introduced. The dispersion equations for acoustic waves and for optical phonons are derived. The properties of piezoelectricity, pyroelectricity, and ferroelectricity are discussed. The attenuation of optical fibres, the operation of a photocopier, and the ability of liquid crystals to rotate polarization are also discussed.

Shape-morphing materials have recently garnered significant attention thanks to their great potential in such fields as robotics, telecommunications, and medicine. Here, we propose a meta-atom chain that is actuated via mutual coupling to achieve the reconfiguration of either the entire structure or its specific portions by selecting the frequency of the excitation voltage. An experiment was designed to verify the actuation mechanisms on a meta-atom chain. Our findings could pave a way for the design of micro-robots, tunable antennas, and on-orbit solar panel assembly.

In this work, the coupling and dispersion characteristics of coalesced resonators as a function of their capacitance is investigated, with the goal of developing novel ways of dispersion control. When planar resonators are coalesced and their shared side is capacitively loaded, the total coupling coefficient is positive, allowing for the propagation of forward magnetoinductive waves. By varying the capacitive load on their shared side, the sign and size of the total coupling can be controlled. This is demonstrated in an 11-element array, where the magnetoinductive wave can switch between forward and backward propagation depending on the capacitive load of the shared side. Furthermore, there is a critical value of the ratio between the capacitive loads on shared and non-shared sides, at which the coupling becomes zero, effectively cutting of wave propagation on the structure. It is shown that the structure can be tuned in two ways: maintain a constant operating frequency while tuning the coupling, or tune the operating frequency while keeping the coupling constant. At the same time, an optimisation procedure for setting up numerical simulations to match the experimental data is proposed. The simulations provided significant insight on the electric coupling's behaviour. Experimental, numerical and analytical data verify this behaviour.

Abstract Uses the classical Curie-Weiss model to explain the mechanisms underpinning the phenomenon of permanent magnetism. Discusses the Curie temperature at which magnetization is lost, the formation and subsequent change in shape of magnetic domains, the nature of domain walls, the hysteresis curve for magnetization and demagnetization, magnetic anisotropy, soft and hard magnetic materials, and the perfomance of the best modern materials. Uses detailed quantum mechanical theory and the periodic table to compare the different forms of magnetism, including paramagnetism, antiferromagnetism, ferromagnetism and ferrimagnetism. Considers additional magnetic phenomena including electron spin resonance, nuclear magnetic resonance, cyclotron resonance, the quantum Hall effect, the magneto-electric effect, magnetoresistance and spin waves. Presents applications for magnetic materials including spintronic devices, Faraday effect isolators, sensors, read heads for magnetic data storage and permanent magnet electric motors.

Time-domain reflectometry of magnetoinductive (MI) waves in metamaterials with inter-element coupling has been previously shown to enable contactless sensing of conductive objects. The basic principle is that conductive objects affect the resonant properties of elements of the array causing reflections of MI waves. In this work we demonstrate high-fidelity signal detection achieved by tuning the driving signal to the passband of MI waves. Feasibility of imaging of inhomogeneous conductive environment and achieving sub-unit-cell accuracy will be discussed, with potential applications ranging from quality control in 3D printing to medical imaging. Analytical, numerical and experimental results will be presented.

Abstract Presents several different and complementary physical pictures for the behaviour of electron waves in periodic arrangements of atoms that each lead to a band theory of solids, including the Kronig-Penney, Ziman, Feynman coupled mode and tight-binding models. Uses these models to introduce the idea of an ‘effective mass’ to predict the response of an electron to an electric field. Shows how the number of free electrons and number of states per band can be calculated, and how metals and insulators can be distinguished on the basis of their numbers of valence electrons. Introduces the idea of a ‘hole’ as an equivalent particle that simplifies description of the absence of an electron. Briefly discusses divalent metals, and the effect of temperature in determining the density of charge carriers available for conduction through the Fermi-Dirac function.

Abstract Reviews the materials and components that are complementary to lasers in optoelectronic systems, starting with the photodiodes needed for light detection and the light emitting diodes used for broadband emission (and especially for energy-efficient lighting). Continues to non-linear optical materials and their applications in volume holography and optical phase conjugation, and the related phenomenon of acousto-optic diffraction. Explains the operation of integrated optic components such as waveguides, modulators and switches used in optical fibre telecommunications, and bulk optical components such as spatial light modulators, non-linear Fabry-Perot cavities, MEMS-based optical scross-connect switches and electro-absorption modulators used in free-space optical systems.

Abstract Describes new artificial materials generally operating in the electromagnetic domain and based either on structured dielectrics (photonic bandgap materials), or combinations of structured dielectrics and metals (metamaterials). Discusses the dielectric properties of arrays of wires and the magnetic properties of arrays of resonant loops such as split ring resonators. Introduces the idea of an effective permittivity and permeability at RF or optical frequency resulting from these ararngements and discusses the new effects that can arise when both are negative (and the refractive index is also negative). Considers applications in the form of photonic bandgap fibres (which can confine light inside a hollow core), the perfect lens (whose resolution can exceed the diffraction limit) and detectors for magnetic resonance imaging (whose periodic construction can provide patient safety in internal imaging).

Abstract A classic text in the field, providing a readable and accessible guide for students of electrical and electronic engineering. The 11th edition includes many new diagrams and photographs illustrating fundamental material properties, measurement systems, and new applications. Ideal for undergraduates, the book is also an invaluable reference for graduate students and others wishing to explore this rapidly expanding field

Magnetic interactions in metamaterial structures have led to a wide variety of applications from wireless power transfer to contactless localisation. Here, we show that in two split ring resonators (SRR), the direction of the induced Lorentz force can be reversed by varying the frequency of the applied AC voltage. An analytical model has been verified by experimental data. These findings have the potential to enable the reconfiguration of programmable structures for new capabilities and functionalities.

In this report, the coupling and dispersion characteristics of discrete and coalesced square resonators was investigated in the MHz regime. Resonators with one and three gaps were considered. When the resonators are not in direct contact, the number of gaps has little effect upon the total coupling, which is negative. When the resonators are connected so that they share one side, the coupling can change drastically depending on the number of gaps. In particular, when the shared side has a gap, the total coupling coefficient switches to positive values, making it possible for forward travelling waves to propagate on arrays. Experimental, numerical and analytical data verify this behaviour.

We review our recent work on unidirectional wave guiding due to interference of magnetoinductive waves. We derive selectivity rules for switchable unidirectional signal guiding and demonstrate that they are governed by dispersion relations. Expanding our analysis to diatomic structures capable of carrying both forward and backward waves, we realise a frequency-controlled switching of unidirectional wave guidance. A variety of scenarios including both 1D and 2D structures, operating either in the MHz or in the THz frequency range will be presented, with Poynting vector analysis used for visualization of unidirectional signal propagation. Our analytical model will be verified with numerical simulations (THz) and experimental data (MHz).