Theory of Dynamic Stripe Induced Superconductivity

Since the recently reported giant isotope effect on T* [1] could be consistently explained within an anharmonic spin-charge-phonon interaction model, we consider here the role played by stripe formation on the superconducting properties within the same model. This is a two-component scenario and we recast its basic elements into a BCS effective Hamiltonian. We find that the stripe formation is vital to high-Tc superconductivity since it provides the glue between the two components to enhance Tc to the unexpectedly large values observed experimentally.Comment: 7 pages, 2 figure

In Situ Characterisation of Permanent Magnetic Quadrupoles for focussing proton beams

High intensity laser driven proton beams are at present receiving much attention. The reasons for this are many but high on the list is the potential to produce compact accelerators. However two of the limitations of this technology is that unlike conventional nuclear RF accelerators lasers produce diverging beams with an exponential energy distribution. A number of different approaches have been attempted to monochromise these beams but it has become obvious that magnetic spectrometer technology developed over many years by nuclear physicists to transport and focus proton beams could play an important role for this purpose. This paper deals with the design and characterisation of a magnetic quadrupole system which will attempt to focus and transport laser-accelerated proton beams.Comment: 20 pages, 42 figure

Universal observation of multiple order parameters in cuprate superconductors

The temperature dependence of the London penetration depth \lambda was measured for an untwined single crystal of YBa_2Cu_3O_{7-\delta} along the three principal crystallographic directions (a, b, and c). Both in-plane components (\lambda_a and \lambda_b) show an inflection point in their temperature dependence which is absent in the component along the c-direction (\lambda_c). The data provide convincing evidence that the in-plane superconducting order parameter is a mixture of s+d-wave symmetry whereas it is exclusively s-wave along the c-direction. In conjunction with previous results it is concluded that coupled s+d-order parameters are universal and intrinsic to cuprate superconductors.Comment: 5 pages, 3 figure

Melanoma of the middle ear: initial presentation, Fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography imaging and follow up

Abstract Background: We present a rare case of primary mucosal melanoma of the middle ear imaged with 18F-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT). Method: Clinical, radiological, intra-operative and histological findings are discussed. Results: An 88-year-old woman presented with intermittent otorrhoea of the left ear for several months. Otoscopy revealed a livid protrusion of the tympanic membrane. Melanoma was not suspected initially, but was established on transmembranous biopsy. Pre-operative 18F-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography revealed a mass lesion in the left tympanic cavity with high fluoro-deoxyglucose uptake, as well as an ipsilateral intraparotid lymph node metastasis. The patient underwent surgical treatment. The diagnosis of melanoma was confirmed histologically. Conclusion: In this rare case, clinical, radiological and surgical findings led to the diagnosis of a primary mucosal melanoma of the middle ea

The polarizability model for ferroelectricity in perovskite oxides

This article reviews the polarizability model and its applications to ferroelectric perovskite oxides. The motivation for the introduction of the model is discussed and nonlinear oxygen ion polarizability effects and their lattice dynamical implementation outlined. While a large part of this work is dedicated to results obtained within the self-consistent-phonon approximation (SPA), also nonlinear solutions of the model are handled which are of interest to the physics of relaxor ferroelectrics, domain wall motions, incommensurate phase transitions. The main emphasis is to compare the results of the model with experimental data and to predict novel phenomena.Comment: 55 pages, 35 figure

Fluctuating Cu-O-Cu Bond model of high temperature superconductivity in cuprates

Twenty years of extensive research has yet to produce a general consensus on the origin of high temperature superconductivity (HTS). However, several generic characteristics of the cuprate superconductors have emerged as the essential ingredients of and/or constraints on any viable microscopic model of HTS. Besides a Tc of order 100K, the most prominent on the list include a d-wave superconducting gap with Fermi liquid nodal excitations, a d-wave pseudogap with the characteristic temperature scale T*, an anomalous doping-dependent oxygen isotope shift, nanometer-scale gap inhomogeneity, etc.. The key role of planar oxygen vibrations implied by the isotope shift and other evidence, in the context of CuO2 plane symmetry and charge constraints from the strong intra-3d Coulomb repulsion U, enforces an anharmonic mechanism in which the oxygen vibrational amplitude modulates the strength of the in-plane Cu-Cu bond. We show, within a Fermi liquid framework, that this mechanism can lead to strong d-wave pairing and to a natural explanation of the salient features of HTS

Oxygen isotope effect on superconductivity and magnetism in Y_1-xPr_xBa_2Cu_3O_7-\delta

Oxygen isotope (^{16}O/^{18}O) effects (OIE's) on the superconducting transition (T_c), the spin-glass ordering (T_g), and the antiferromagnetic ordering (T_N) temperatures were studied for Y_1-xPr_xBa_2Cu_3O_7-\delta as a function of Pr content (0.0\leq x \leq 1.0). The OIE on T_c increases with increasing x up to x\approx0.55, where superconductivity disappears. For decreasing x the OIE's on T_N and T_g increase down to x\approx 0.7 where antiferromagnetic order and down to x\approx0.3 where spin-glass behavior vanish, respectively. The OIE's on T_g and T_N are found to have {\it opposite signs} as compared to the OIE on T_c. All OIE's are suggested to arise from the isotope dependent mobility (kinetic energy) of the charge carriers.Comment: 5 pages, 3 figures, 1 tabl