Observation of large h/2eh/2e and h/4eh/4e oscillations in a proximity dc superconducting quantum interference device

We have measured the magnetoresistance of a dc superconducting quantum interference device in the form of an interrupted mesoscopic normal-metal loop in contact with two superconducting electrodes. Below the transition temperature of the superconducting electrodes, large $h/2e$ periodic magnetoresistance oscillations are observed. By adding a small dc bias to the ac measurement current, $h/4e$ oscillations can be produced. Lowering the temperature further leads to even larger oscillations, and eventually to sharp switching from the superconducting state to the normal state. This flux-dependent resistance could be utilized to make highly sensitive flux detector.Comment: One pdf file, 4 pages, 4 figure. For figure 1, a smaller file is uploade

Cherry Island. Assessing the Behavior of a Large Landfill Using Geotechnical Instrumentation

The 513-acre Cherry Island Landfill is located at the junction of the Delaware and Christina Rivers near Wilmington, Delaware. Today the landfill receives approximately 1,850 tons of waste per day. The landfill was constructed directly on soft dredge materials and river deposits which act as a natural liner. Due to the unique geotechnical characteristics at the site, potentially large deformation and slope stability were concerns during the planning and development of the landfill due to the expected high rates of waste placement. Slope stability and finite difference analysis were performed to develop adequate filling plans to cope with the expected high rates of waste placement. In addition, approximately 300 geotechnical instruments were installed during and after construction. These instruments include inclinometers, open standpipe piezometers, vibrating wire piezometers, pneumatic piezometers, settlement plates, vibrating wire thermistors, and pneumatic total pressure cells. To process and evaluate the large amount of data collected every month, a Geographical Information System (GIS) was incorporated which allows rapid visualization of important parameters. The results obtained from the analysis together with the instrumentation data provide a special insight into the behavior of large landfills constructed on soft soils. This paper presents a discussion of the procedures for analysis and monitoring of the landfill and the main results obtained. This paper also describes the issues involved in installing and maintaining instrumentation for this type of application

Interaction-induced shift of the cyclotron resonance of graphene using infrared spectroscopy

We report a study of the cyclotron resonance (CR) transitions to and from the unusual $n=0$ Landau level (LL) in monolayer graphene. Unexpectedly, we find the CR transition energy exhibits large (up to 10%) and non-monotonic shifts as a function of the LL filling factor, with the energy being largest at half-filling of the $n=0$ level. The magnitude of these shifts, and their magnetic field dependence, suggests that an interaction-enhanced energy gap opens in the $n=0$ level at high magnetic fields. Such interaction effects normally have limited impact on the CR due to Kohn's theorem [W. Kohn, Phys. Rev. {\bf 123}, 1242 (1961)], which does not apply in graphene as a consequence of the underlying linear band structure.Comment: 4 pages, 4 figures. Version 2, edited for publication. Includes a number of edits for clarity; also added a paragraph contrasting our work w/ previous CR expts. in 2D Si and GaA

Reversing non-local transport through a superconductor by electromagnetic excitations

Superconductors connected to normal metallic electrodes at the nanoscale provide a potential source of non-locally entangled electron pairs. Such states would arise from Cooper pairs splitting into two electrons with opposite spins tunnelling into different leads. In an actual system the detection of these processes is hindered by the elastic transmission of individual electrons between the leads, yielding an opposite contribution to the non-local conductance. Here we show that electromagnetic excitations on the superconductor can play an important role in altering the balance between these two processes, leading to a dominance of one upon the other depending on the spatial symmetry of these excitations. These findings allow to understand some intriguing recent experimental results and open the possibility to control non-local transport through a superconductor by an appropriate design of the experimental geometry.Comment: 6 pages, 3 figure

Multicomponent fractional quantum Hall effect in graphene

We report observation of the fractional quantum Hall effect (FQHE) in high mobility multi-terminal graphene devices, fabricated on a single crystal boron nitride substrate. We observe an unexpected hierarchy in the emergent FQHE states that may be explained by strongly interacting composite Fermions with full SU(4) symmetric underlying degrees of freedom. The FQHE gaps are measured from temperature dependent transport to be up 10 times larger than in any other semiconductor system. The remarkable strength and unusual hierarcy of the FQHE described here provides a unique opportunity to probe correlated behavior in the presence of expanded quantum degrees of freedom.Comment: 5 pages, 3 figure

Spin and valley quantum Hall ferromagnetism in graphene

In a graphene Landau level (LL), strong Coulomb interactions and the fourfold spin/valley degeneracy lead to an approximate SU(4) isospin symmetry. At partial filling, exchange interactions can spontaneously break this symmetry, manifesting as additional integer quantum Hall plateaus outside the normal sequence. Here we report the observation of a large number of these quantum Hall isospin ferromagnetic (QHIFM) states, which we classify according to their real spin structure using temperature-dependent tilted field magnetotransport. The large measured activation gaps confirm the Coulomb origin of the broken symmetry states, but the order is strongly dependent on LL index. In the high energy LLs, the Zeeman effect is the dominant aligning field, leading to real spin ferromagnets with Skyrmionic excitations at half filling, whereas in the `relativistic' zero energy LL, lattice scale anisotropies drive the system to a spin unpolarized state, likely a charge- or spin-density wave.Comment: Supplementary information available at http://pico.phys.columbia.ed

Progress in the Fremantle Primary Prevention Study- A Pilot Study of Risk Factor Modification for Cardiovascular Disease

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality in 40-80year olds in Australia. Many of the risk factors though modifiable are often undiagnosed and hence untreated. Increasingly, general practice is recognised as being well positioned but under-utilised in attempts to improve primary prevention. The study aims to monitor the changes in CVD risk following delivery of high and low intervention strategies at the GP level. Methods: 1200 participants in total were recruited during routine surgery attendances from 3 WA general practices since November 2006. Baseline data was collected on all. One group then received standard care as per best practice guidelines with 3 monthly follow-up to 12 months. The second group received standard care as per best practice guidelines delivered by their GP with no scheduled interim follow-up but with follow-up at 12 months after study commencement. Data on risk factor indicators was measured at each contact and a composite score on global cardiovascular risk calculated using the New Zealand Risk Calculator. Principal Findings: In January 2008, data was recorded on 1178 participants at baseline (22 withdrew), 3 month data on 537, 6 month data on 458 and 9 month on 272 and 12 month data on 96. Interim data will be presented. While a significant proportion of the community are already known to have cardiovacular risk factors, GPs and their practice staff are ideally positioned to assess the extent of this potential morbibity and institute treatment modalities and programs to reverse and modify them

An investigation into E-business service in the UK telecommunication manufacturing industry

Nowadays, suppliers’ product and service quality has risen in importance with a manufacturer’s push to develop core competencies and capitalise on global operations and markets. However, due to the complex features of business service, suppliers are facing significant challenges in providing service effectively and developing business collaboration. This is further complicated by the development of information and communication technologies (ICTs). This paper thus attempts to investigate the factors influencing buyers’ e-service (EBS) requirements and the impact of these requirements on business collaboration. Based on a questionnaire survey with 500 UK telecommunication manufacturers, this research identifies buyers’ different EBS requirements for different types of suppliers and the impact of ICTs on EBS requirements. While for suppliers our findings provide insights into buyers’ EBS requirements, they can help buyers to develop appropriate supplier selection criteria. The findings also contribute to a better understanding of the development of buyer and supplier business collaboration