Combinatorial synthesis and screening of chalcogenide materials for data storage

For more than 15 years researchers at the Optoelectronics Research Centre at the University of Southampton have been developing novel compositions of chalcogenide glasses for a wide range of optical applications. Recently this expertise has been combined with those of Ilika Technologies Ltd and the School of Chemistry to focus on the development of enhanced chalcogenide materials for OUM and optical data storage applications. In our talk, we report on our high throughput methodology which allows rapid, reproducible and comprehensive mapping of phase diagrams and screening of optical, thermal and electrical properties. These procedures were initially applied to Ge:Sb:Te compositions where we were able to synthesis and analyse over 4000 sample points spanning the entire ternary system. In order to process such large volumes of compositions, novel screening techniques and strategies have been employed. We are applying this methodology to other novel compositions and our findings are reported

Crystallisation study of the Cu₂ZnSnS₄ chalcogenide material for solar applications

Second generation thin-film chalcogenide materials, in particular CuInGa(S,Se)2 (CIGS) and CdTe, have been among the most promising and quickly became commercial candidates for large-scale PV manufacturing. These materials offer stable and efficient (above 10%) photovoltaic modules fabricated by scalable thin-film technologies and cell efficiencies above 20 % (CIGS). Indium-free kesterite-related materials such as Cu2ZnSnS4 have attracted significant research interest due to their similar properties to CIGS. In these materials, indium is replaced with earth-abundant zinc and tin metals. The quaternary semiconductor Cu2ZnSnS4(CZTS) is a relatively new photovoltaic material and is expected to be interesting for environmentally amenable solar cells, as its constituents are nontoxic and abundant in the Earth's crust. The CZTS thin films show p-type conductivity, a band gap of 1.44–1.51 eV that is ideal to achieve the highest solar-cell conversion efficiency, and relatively high optical absorption in the visible light range

Ultra low power consuming thermally stable sulphide materials for resistive and phase change memristive application

The use of conventional chalcogenide alloys in rewritable optical disks and the latest generation of electronic memories (phase change and nano-ionic memories) has provided clear commercial and technological advances for the field of data storage, by virtue of the many well-known attributes, in particular scaling, cycling endurance and speed, that these chalcogenide materials offer. While the switching power and current consumption of established germanium antimony telluride based phase change memory cells are a major factor in chip design in real world applications, the thermal stability and high on-state power consumption of these device can be a major obstacle in the path to full commercialization. In this work we describe our research in material discovery and prototype device fabrication and characterization, which through high throughput screening has demonstrated thermally stable, low current consuming chalcogenides for applications in PCRAM and oxygen doped chalcogenides for RRAM which significantly outperform the current contenders

Countering Quantum Noise with Supplementary Classical Information

We consider situations in which i) Alice wishes to send quantum information to Bob via a noisy quantum channel, ii) Alice has a classical description of the states she wishes to send and iii) Alice can make use of a finite amount of noiseless classical information. After setting up the problem in general, we focus attention on one specific scenario in which Alice sends a known qubit down a depolarizing channel along with a noiseless cbit. We describe a protocol which we conjecture is optimal and calculate the average fidelity obtained. A surprising amount of structure is revealed even for this simple case which suggests that relationships between quantum and classical information could in general be very intricate.Comment: RevTeX, 5 pages, 2 figures Typo in reference 9 correcte

Surface superconductivity and order parameter suppression in UPt3_3

We show that a recent measurement of surface superconductivity in UPt$_3$ (Keller {\it et. al.}, Phys. Rev. Lett. {\bf 73}, 2364 (1994)) can be understood if the superconducting pair wavefunction is suppressed anisotropically at a vacuum to superconductor interface. Further measurements of surface superconductivity can distinguish between the various phenomenological models of superconducting UPt$_3$.Comment: 4 pages, latex, 2 Figures available upon request ([email protected]

Membrane paradigm realized?

Are there any degrees of freedom on the black hole horizon? Using the `membrane paradigm' we can reproduce coarse-grained physics outside the hole by assuming a fictitious membrane just outside the horizon. But to solve the information puzzle we need `real' degrees of freedom at the horizon, which can modify Hawking's evolution of quantum modes. We argue that recent results on gravitational microstates imply a set of real degrees of freedom just outside the horizon; the state of the hole is a linear combination of rapidly oscillating gravitational solutions with support concentrated just outside the horizon radius. The collective behavior of these microstate solutions may give a realization of the membrane paradigm, with the fictitious membrane now replaced by real, explicit degrees of freedom.Comment: 8 pages, Latex, 3 figures (Essay given second place in Gravity Research Foundation essay competition 2010

Antiferromagnetic Domains and Superconductivity in UPt3

We explore the response of an unconventional superconductor to spatially inhomogeneous antiferromagnetism (SIAFM). Symmetry allows the superconducting order parameter in the E-representation models for UPt3 to couple directly to the AFM order parameter. The Ginzburg-Landau equations for coupled superconductivity and SIAFM are solved numerically for two possible SIAFM configurations: (I) abutting antiferromagnetic domains of uniform size, and (II) quenched random disorder of `nanodomains' in a uniform AFM background. We discuss the contributions to the free energy, specific heat, and order parameter for these models. Neither model provides a satisfactory account of experiment, but results from the two models differ significantly. Our results demonstrate that the response of an E_{2u} superconductor to SIAFM is strongly dependent on the spatial dependence of AFM order; no conclusion can be drawn regarding the compatibility of E_{2u} superconductivity with UPt3 that is independent of assumptions on the spatial dependence of AFMComment: 12 pages, 13 figures, to appear in Phys. Rev.

Magnetic Field Effects on Neutron Diffraction in the Antiferromagnetic Phase of UPt3UPt_3

We discuss possible magnetic structures in UPt$_3$ based on our analysis of elastic neutron-scattering experiments in high magnetic fields at temperatures $T<T_N$. The existing experimental data can be explained by a single-{\bf q} antiferromagnetic structure with three independent domains. For modest in-plane spin-orbit interactions, the Zeeman coupling between the antiferromagnetic order parameter and the magnetic field induces a rotation of the magnetic moments, but not an adjustment of the propagation vector of the magnetic order. A triple-{\bf q} magnetic structure is also consistent with neutron experiments, but in general leads to a non-uniform magnetization in the crystal. New experiments could decide between these structures.Comment: 5 figures included in the tex

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results