Solid State Physics

Linear elastic fracture mechanics (LEFM) and the secant-intercept procedure have been used to determine that fracture toughness (KIC), critical elastic energy release rate per crack-tip extension (GIC) and plastic-zone radius for local steel, ST 60Mn product of Delta Steel Company, Aladja, Nigeria. The results show that the product is high-strength steel of low ductility.

We propose a microphysical theory of the triboelectric effect by which mechanical rubbing separates charges across the interface between two surfaces. Surface electrons are treated as an open system, weakly coupled to two baths, corresponding to the bulk materials. We show that work can be extracted from the motion-induced population inversion of fermions, thus extending and generalizing Zel'dovich's theory of bosonic superradiance. We argue that this is consistent with the basic phenomenology of triboelectrification and triboluminescence as off-equilibrium processes.

Among the multiple applications of Light emitting diodes (LEDs), archaeology and earth sciences have benefited too concerning the determination of time (chronology) based on the thermoluminescene (TL) and optically stimulated luminescence (OSL) method of dating artifacts, material culture of archaeological and geoarchaeological significance. Blue Light emitting diodes (LED) is mostly used for stimulation and bleaching of luminescence, in lieu of green and IR LEDs. Ancient inorganic materials made of geological rocks (carving, knapping, mixing, firing) are either fired in antiquity above 450 o C or sun exposed for a short time (surface luminescence dating) and thus the electron traps are completely bleached for the "zero time" clock to set up. The importance of blue LEDs in archaeology was the research product of 2014 Nobel Prize in Physics. On the occasion of blue LED invention and Nobel Prize we offer an extended overview of the development of semiconductor physics focuse...

This thesis contains a theoretical treatment of the time-dependent quantum transport of electrons through molecular junctions. In particular, the nonequilibrium Green's function (NEGF) method is used to obtain the time-dependent current and current fluctuations in response to an arbitrarily time-dependent spatially homogeneous bias in the leads and molecular region. All subsystems in the nanojunction are assumed to be noninteracting throughout, and in addition the wide-band limit approximation (WBLA) is made in order to simplify the treatment of the lead-molecule coupling.

The theoretical work involves a complete analytical solution in the two-time plane of the Kadanoff-Baym equations for all components of the molecular region Green's function defined on the imaginary time Konstantinov-Perel' contour. This enables the derivation of expressions for time-dependent quantities such as the particle number in the molecular region and a generalized time-dependent Landauer-Büttiker (LB) formula for the current through an arbitrarily large conducting molecule. The partition-free approach is assumed for the switch-on of a bias in the leads, which enables us to study the effects on the transient transport of the initial coupling between the subsystems of the nanojunction.

The analytical expression for the full two-time Green's function is then used to study the quantum correlations between currents in the different leads. Using many-body methods, the two-time current correlation function is expressed in terms of a matrix product of Green's functions which are all known exactly. Therefore, in similar fashion to the generalized LB current, the current correlations generalize the LB theory of shot and thermal noise so that it is (i) partition-free and (ii) valid for an arbitrary time-dependent bias. To check its generality, this formula is shown to reproduce results for the zero- and finite-frequency current noise that are known from the literature on this topic.

The formulas for the current and current fluctuations are originally obtained in terms of integrals over the frequency and time planes. To render these formulas useful for calculations on large molecules they are then re-expressed with all frequency integrals replaced with special functions, which may be computed via the Padé expansion of the Fermi function. This results in a formalism which is ideally multiscale in time, i.e. which does not get more expensive with increasing number of time steps, and which can therefore be used to study the short-time transient and steady-state transport quantities with identical computational expense. Some numerical calculations of the current and noise response to the switch-on of a time-dependent bias are then performed.

The first kind of time-dependent driving considered in this thesis is periodic. Some preliminary calculations are performed on periodically-driven quantum dots, and the effect on the current of varying the driving frequency, temperature, lead-molecule coupling and driving amplitude is studied. Next, the problem of quantum pumping is considered, and sufficient conditions are found for a periodically driven system with zero time-average bias to generate a net time-averaged current through the system. The effects of finite size on the current response to static and periodic biases are investigated, again using the molecular wire as an illustrative model. Next, calculations of the quantum pump current are presented for a particular biharmonic bias model, and in particular the effect on this current of breaking the sinusoidal shape of the driving field. Finally, the discussion turns to calculations of the cross-lead current correlations in extended systems in response to static and periodic biases. By investigating molecular wires of different lengths and internal hopping parameters, a signature of the traversal time for electrons crossing the sample is found in both the transient and steady-state cross-lead current correlations.

As there are no restrictions on the nature of the time-dependent bias driving the system out of equilibrium, one can use this formalism to study the electronic response to a classically fluctuating bias in the leads. The second kind of time-dependent driving studied in this thesis is therefore non-deterministic, and exact formulas for the bias-averaged current response to a stochastic bias are derived for the first time. This problem is formally analogous to the use of the Langevin equation approach to obtain a relation between the conductance in a classical circuit and the strength of fluctuations in an external driving bias: the so-called Nyquist theorem. An exact quantum version of the Nyquist theorem is derived for a driving bias with colour noise which relates the strength of fluctuations, the correlation time of fluctuations, the temperature and conductance in a molecular junction. Due to the nonlinear relation between current and driving bias in these junctions, it is not always true that the conductance will decrease with increasing fluctuation strength. Instead, there can be particular intermediate values of the fluctuation strength at which peaks in the conductance are observed, in a stochastic resonance effect.

— A nanocrystallineCdS film can be deposited by chemical bath deposition using non aqueous medium. XRD analysis confirms the crystalline structure of CdS (002) with 34 nm crystallite size. The as deposited films are stoichiometric in nature with Cd and S atomic % ratio equal to 1.0. The field emission scanning electron miceoscope and atomic force microscopy studies revels a densely packed non porous granular deposit with RMS value of roughness equal to 92nm. The band gap of the film is measures by spectroscopy and it is observed to 2.40 eV which is good agreement with the reported result. The photoluminescence prominent peak of the CdS film is observed to be 392 nm.

The selection of nanoparticles for achieving efficient contrast for biological and cell imaging applications, as well as for photothermal therapeutic applications, is based on the optical properties of the nanoparticles. We use Mie theory and discrete dipole approximation method to calculate absorption and scattering efficiencies and optical resonance wavelengths for three commonly used classes of nanoparticles: gold nanospheres, silica-gold nanoshells, and gold nanorods. The calculated spectra clearly reflect the well-known dependence of nanoparticle optical properties viz. the resonance wavelength, the extinction cross-section, and the ratio of scattering to absorption, on the nanoparticle dimensions. A systematic quantitative study of the various trends is presented. By increasing the size of gold nanospheres from 20 to 80 nm, the magnitude of extinction as well as the relative contribution of scattering to the extinction rapidly increases. Gold nanospheres in the size range comm...

The difference between conductors, insulators and semiconductors is to plot the available energies for electrons in the materials. Instead of having discrete energies as in the case of free atoms, the available energy states form bands. Energy bands occur in solids where the discreet energy levels of the individual atoms merge into bands which contain a large number of closely spaced energy levels.

A superluminal quantum-vortex model of the electron and the positron is produced from a superluminal double-helix model of the photon during electron-positron pair production. The two oppositely-charged (with Q = ±e sqrt (2/α) = 16.6e) open-helix spin-½ half-photons compose the double-helix photon. These half-photons separate and curl up their separated superluminal single-helical trajectories to form an electrically-charged superluminal closed-helix spin-½ quantum-vortex electron model and a corresponding positron model. The helical radius and the Dirac equation's zitterbewegung angular frequency of the quantum vortex electron and positron models equal the helical radius and zitterbewegung angular frequency of the two spin-½ half-photons, each of energy E = mc^2 , that composed the double-helix photon model of energy E = 2mc^2 from which the electron and positron models were produced. The photon and electron models are also compatible when a photon of energy E > 2mc^2 produces a relativistic electron-positron pair. Implications of the quantum vortex electron model for electron stability are discussed.

The dependence of carrier effective mass of GaN x As 1 − x , InN x P 1 − x , InN x As 1 − x , and InN x Sb 1 − x alloys on nitrogen content is investigated using a 10-band k.p model. The electron effective mass m e ⁎ at the bottom of conduction band in GaN x As 1 − x and InN x P 1 − x exhibits a gradual increase as a function of N concentration in the range 0− 1% and a decrease of x value between 1 and 5%. However, the behavior of m e ⁎ in InN x As 1 − x and InN x Sb 1 − x shows a strong decrease in all studied x-range. Our results are compared to the available data reported in the literature. On the other hand, contrary to heavy-hole effective mass m hh ⁎ , the light-hole effective mass m lh ⁎ in all studied alloys is significantly affected by nitrogen states, which modify the non-parabolicity of the LH band. The modification of the carrier effective mass affects the transport properties of the III-N-V alloys.

This essay evolved from my realization that physics has become a moribund science and when even a recent winner of the Nobel prize in Physics (1998) cannot create a ripple in the reductionist programme that fights long and hard to remain at the center of publicly-funded science that has been central to the modern viewpoint of Western Civilization. Contrary to the opinions of most well-educated intellectuals, who have been deeply influenced by the Abstract Ideas of this abstract science, most people have little knowledge of the limited progress that has been made since the physicists made their historic Faustian deal with the modern state and its military. Philosophers have been ejected from the subject that was originally known as Natural Philosophy as they have always offered (since Isaac Newton) subtle critiques of the basic assumptions of this mathematical science and now they would be deeply embarrassed by this self-congratulatory tribe of elitists. The author, Bob Laughlin is still a senior statesman of science, long-time Professor of Physics at Stanford, where he has taught since 1985. Now he is a visiting scholar at major research institutes in Asia. However, he has had an epiphany that we have been thinking about physics in a incorrect way, resulting in an endless (and expensive) reductionist quest for the Ultimate Small Thing. He now alerts us to a major new idea that is growing quietly in the Theatre of Science: Emergence where the usual properties of matter (we are already familiar with) arise from the organization of large numbers of atoms; not from obscure mathematical equations that usually resist interpretation, as well as analytic solutions. This is NOT the message that most of his fellow physicists even want to discuss, never mind reject. When senior academics have invested their whole lives in techniques, concepts and assumptions then a major reversal of basic direction is far too threatening. Laughlin is so radical that he now proposes that central foundations of this core science, such as Newton's classical Laws of Motion and the sacred Rules of Quantum Mechanics (QM) are themselves 'emergent'. The exactness of those astonishing measurements (to 14 digits no less) is shown to be an illusion.

This Impact Report identifies and summarises the diverse impacts, resulting from the £500m of UK funding of Science and Technology in 2013, using numerous quantitative metrics and short case study extracts.  It shows how the varied impacts of a national science and technology organization and its many funded programmes can be annually identified, captured, tracked, and summarised in a public document.

The report was produced for, and by, the Science and Technology Facilities Council (STFC) -  the UK Research Council responsible for funding: (1) all UK astronomy, particle and nuclear physics research, (2) related UK science and technology facilities (e.g. as Harwell and Daresbury), (3) the UK contribution to international science (e.g. CERN, international telescopes and space missions), (4) innovation and business spin-off programmes, and (5) UK public engagement activities.

The Report was co-researched and co-authored by the STFC Impact Team, including myself while Impact Evaluation Manager in 2013, with Dr. Claire Dougan-McCallie (lead author/Head of Impact) and Jenny Beard, with additional input from senior managers, and many data and case study contributions from other key managers across STFC.

Varied key impacts are identified and reported including:

• Research amongst the best (by citation impact) in astronomy, nuclear and particle physics.
• Supported research of 226 Principal Investigators in 70 universities, led to 1,100 peer-reviewed papers in 2012.
• Facilities (the Diamond Light Source, ISIS and CLF) were used in 2012/13 by over 4,200 unique users , in over 2,400 experiments, producing over 1,000 papers in peer-reviewed journals.

• Technology from CERN benefited the UK economy by over £100 billion every year.
• Funding the development of the UK’s space, internet and computer animation industries, returned over £500 billion to the UK economy per annum.
• Funded Innovation Campuses hosted over 230 enterprises and supported over 5,000 jobs.
• UK industry won £43 million in contracts from the international subscriptions funded, and had accumulated a total of £150 million since 2005.

• Funded research inspired future generations to study STEM subjects, attracting 90% of UK undergraduates to study physics, funded 782 PhD students  and 16,800 student training days.
• Between 2009 to 2012 public engagement programmes engaged people on 58 million occasions, with 2 million people engaged in face-to-face activities in 2013 alone.

Tin oxide nanoparticles ranging in average size from 12 to 315 nm have been prepared by levitation-jet aerosol synthesis through condensation of tin vapor in a flow of inert gases and oxygen (air). The nanoparticles have been characterized by transmission electron microscopy, X-ray diffraction, BET measurements, vibrating sample magnetometry, and Raman scattering spectroscopy. The results indicate that the nanoparticles may exhibit room-temperature ferromagnetism, with their magnetization having a maximum at O:Sn = 1. The ferromagnetic order is tentatively attributed to the presence of localized states on the Sn/SnO and SnO/SnO2 interfaces.

Lorsqu'un corps est soumis à des contraintes externes, celui-ci subit des déformations qui dépendent de l'intensité de ces contraintes. Si ces dernières sont faibles, on observe expérimentalement que les déformations sont proportionnelles aux tensions appliquées. La constante de proportionnalité est une caractéristique du matériau et du type de déformation subi par celui-ci.

Universe is made up of God Particles or Basic Building Blocks ( Fig -1) or mind and mass . To Understand life ( new definition ) we have to understand  sleeping and arousal phenomenon  in living animals , plants and  seed ,  molecules , atoms , particles and in Tachyons which are made up off two God particles . We are set of informations ( Code PcPs ) and that too changing ( fetus , infant , adolescence , adult , old age and finally death ) . Death set of informations ( code PcPs ) are different than life set of informations ( CodePcPs) . Life set of  Informations could be recreated only by Almighty B.B.B . Hence death is illusion. In all stages of set of informations of  particles , atoms, molecules  have arousal state of mind ( Eyes open ) . Hence Idols  are alive  by virtue of arousal -  sleep  phenomenon property ( property of life ) of God particles ( Mind and Mass ) . Life effects are higher thought expressions of B.B.Bs . When these thought expressions are inhibited death thoughts are  triggered , we observe death effects . ( autolysis of cells  and rigor mortis etc ). Hence concept of soul is myth. Hence Life means sleep and arousal phenomenon ( new definition ) . Hence statues are alive because they are in arousal state of mind . ( Open eyes ) till creation exists . After the creation is over,  all stages of God particles would come in sleeping state  in symmetry phase  ( close eyes –mind ) but alive ( new definition ) . Universe “I” is always Alive ( new definition ) whether it is in sleeping state of mind or arousal state of mind.

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