Inhomogeneous vortex-state-driven enhancement of superconductivity in nanoengineered ferromagnet-superconductor heterostructures

Thin film heterostructures provide a powerful means to study the antagonism between superconductivity (SC) and ferromagnetism (FM). One interesting issue in FM-SC hybrids which defies the notion of antagonistic orders is the observation of magnetic field induced superconductivity (FIS). Here we show that in systems where the FM domains/islands produce spatial inhomogeneities of the SC order parameter, the FIS can derive significant contribution from different mobilities of the magnetic flux identified by two distinct critical states in the inhomogeneous superconductor. Our experiments on nanoengineered bilayers of ferromagnetic CoPt and superconducting NbN where CoPt/NbN islands are separated by a granular NbN, lend support to this alternative explanation of FIS in certain class of FM-SC hybrids.Comment: 5 figure

A single molecule switch based on two Pd nanocrystals linked by a conjugated dithiol

Tunneling spectroscopy measurements have been carried out on a single molecule device formed by two Pd nanocrystals (dia, $\sim$5 nm) electronically coupled by a conducting molecule, dimercaptodiphenylacetylene. The I-V data, obtained by positioning the tip over a nanocrystal electrode, exhibit negative differential resistance (NDR) on a background M-I-M characteristics. The NDR feature occurs at $\sim$0.67 V at 300 K and shifts to a higher bias of 1.93 V at 90 K. When the tip is held in the middle region of the device, a coulomb blockade region is observed ($\pm\sim$0.3 V).Comment: Accepted in Praman

Cu K-absorption edge study of cuprate superconductors

Cu K-absorption edges of YBa2Cu3O6.9, Tl2CaBa2Cu2O8 and Bi2CaSr2Cu2O8 show similar features. Copper is mainly in the 2+ state in these cuprates suggesting the likely presence of oxygen holes

Experimental and theoretical electronic charge densities in molecular crystals

Electronic charge density distribution in molecular systems has been described in terms of the topological properties. After briefly reviewing methods of obtaining charge densities from X-ray diffraction and theory, typical case studies are discussed. These studies include rings and cage systems, hydrogen bonded solids, polymorphic solids and molecular NLO materials. It is shown how combined experimental and theoretical investigations of charge densities in molecular crystals can provide useful insights into electronic structure and reactivity

Towards the model driven organization

Todays modern organization is faced with a need for rapid response to changes from external business pressures by updating systems and operational procedures. The effect of such continuous evolution eventually leads to sub- optimal configurations of its underlying systems. The management of continuous business change is compromised by uncertainty due to the inadequacy of existing mechanisms for responding to multiple change drivers thus leading to signifi- cant organizational costs. This represents a major opportunity for seeking greater efficiencies. To date, there has been little or no attempt to apply model driven principles or approaches to addressing these issues. We present a new vision of a Model Driven Organisation (MDO) that has the potential to increase produc- tivity by promoting integration of business processes and collaborations across the organisation whilst supporting safe and convenient adaptations that enable rapid response to change whilst maintaining integrity of the systems within the organisation. The approach proposed is based on the use of modelling languages and simulation technologies that support abstractions for understanding business goals through to specification of IT systems and ultimately to deployed systems. The paper motivates the problem and proposes a definition of the MDO. We val- idate the proposal through an illustrative case and conclude with a review of the state of the art leading to a roadmap of research and emergent grand challenges towards achieving the MDO vision

A novel method of preparing thiol-derivatised nanoparticles ofgold, platinum and silver forming superstructures

Thiol-derivatised nanoparticles of Au, Pt and Ag (diameter 1-10 nm) forming superstructures, are prepared by the acid-facilitated transfer of well characterized particles in a hydrosol to a toluene layer containing the thiol

Surfactant-promoted formation of fractal and dendritic nanostructures of gold and silver at the organic-aqueous interface

The effect of surfactants such as tetraoctylammoniumbromide (TOAB) and cetyltrimethylammoniumbromide (CTAB) on the type of nanostructures formed when gold ions present in the organic phase are reduced at the interface by hydrazine in the aqueous phase has been investigated. Extended fractal structures are formed at the liquid-liquid interface, the fractal structures themselves comprising cauliflower type units formed by gold nanorods. Accordingly, the nanostructures exhibit transverse and longitudinal plasmon adsorption bands in the 550 and 800 nm regions, respectively. Dendritic structures of silver are formed at the interface when Ag ions are reduced similarly in the presence of surfactants. The nanostructures consist of nanoparticles or nanorods with five-fold symmetry

Effect of size on the Coulomb staircase phenomenon in metal nanocrystals

The Coulomb staircase in polymer-covered Pd and Au nanocrystals of varying diameters in the 1.7-6.4 nm has been investigated by employing tunneling conductance measurements. Charging up to several electrons is observed at room temperature in the I-V data. Small nanocrystals show charging steps exceeding 200 mV while the larger ones exhibit smaller steps. Significantly, the charging energies follow a scaling law of the form, U=A+B/d, where d is the diameter of the nanocrystal. Furthermore, the line widths in the derivative spectra also vary inversely with the diameter

Dip-pen lithography using aqueous metal nanocrystal dispersions

Dip-pen lithography has been successfully demonstrated on mica substrates employing hydrosols of polyvinylpyrrolidone-capped Pd nanocrystals as well as Au nanocrystals stabilized by tetrakishydroxymethyl phosphonium chloride. Lines of widths as small as 30 nm and various aspect ratios have been successfully drawn by this method