What can the SNO Neutral Current Rate teach us about the Solar Neutrino Anomaly

We investigate how the anticipated neutral current rate from $SNO$ will sharpen our understanding of the solar neutrino anomaly. Quantitative analyses are performed with representative values of this rate in the expected range of $0.8 - 1.2$. This would provide a $5 - 10 \sigma$ signal for $\nu_e$ transition into a state containing an active neutrino component. Assuming this state to be purely active one can estimate both the $^8B$ neutrino flux and the $\nu_e$ survival probability to a much higher precision than currently possible. Finally the measured value of the $NC$ rate will have profound implications for the mass and mixing parameters of the solar neutrino oscillation solution.Comment: Brief discussion on the first NC result from SNO added; final version to be published in the MPL

Universality of scanning tunneling microscopy in cuprate superconductors

We consider the problem of local tunneling into cuprate superconductors, combining model based calculations for the superconducting order parameter with wavefunction information obtained from first principles electronic structure. For some time it has been proposed that scanning tunneling microscopy (STM) spectra do not reflect the properties of the superconducting layer in the CuO$_2$ plane directly beneath the STM tip, but rather a weighted sum of spatially proximate states determined by the details of the tunneling process. These "filter" ideas have been countered with the argument that similar conductance patterns have been seen around impurities and charge ordered states in systems with atomically quite different barrier layers. Here we use a recently developed Wannier function based method to calculate topographies, spectra, conductance maps and normalized conductance maps close to impurities. We find that it is the local planar Cu $d_{x^2-y^2}$ Wannier function, qualitatively similar for many systems, that controls the form of the tunneling spectrum and the spatial patterns near perturbations. We explain how, despite the fact that STM observables depend on the materials-specific details of the tunneling process and setup parameters, there is an overall universality in the qualitative features of conductance spectra. In particular, we discuss why STM results on Bi$_2$Sr$_2$CaCu$_2$O$_8$ and Ca$_{2-x}$Na$_x$CuO$_2$Cl$_2$ are essentially identical

Interpretation of scanning tunneling quasiparticle interference and impurity states in cuprates

We apply a recently developed method combining first principles based Wannier functions with solutions to the Bogoliubov-de Gennes equations to the problem of interpreting STM data in cuprate superconductors. We show that the observed images of Zn on the surface of Bi$_2$Sr$_2$CaCu$_2$O$_8$ can only be understood by accounting for the tails of the Cu Wannier functions, which include significant weight on apical O sites in neighboring unit cells. This calculation thus puts earlier crude "filter" theories on a microscopic foundation and solves a long standing puzzle. We then study quasiparticle interference phenomena induced by out-of-plane weak potential scatterers, and show how patterns long observed in cuprates can be understood in terms of the interference of Wannier functions above the surface. Our results show excellent agreement with experiment and enable a better understanding of novel phenomena in the cuprates via STM imaging.Comment: 5 pages, 5 figures, published version (Supplemental Material: 5 pages, 11 figures) for associated video file, see http://itp.uni-frankfurt.de/~kreisel/QPI_BSCCO_BdG_p_W.mp

Turbulent Supernova Shock Waves and the Sterile Neutrino Signature in Megaton Water Detectors

The signatures of sterile neutrinos in the supernova neutrino signal in megaton water Cerenkov detectors are studied. Time dependent modulation of the neutrino signal emerging from the sharp changes in the oscillation probability due to shock waves is shown to be a smoking gun for the existence of sterile neutrinos. These modulations and indeed the entire neutrino oscillation signal is found to be different for the case with just three active neutrinos and the cases where there are additional sterile species mixed with the active neutrinos. The effect of turbulence is taken into account and it is found that the effect of the shock waves, while modifed, remain significant and measurable. Supernova neutrino signals in water detectors can therefore give unambiguous proof for the existence of sterile neutrinos, the sensitivity extending beyond that for terrestial neutrino experiments. In addition the time dependent modulations in the signal due to shock waves can be used to trace the evolution of the shock wave inside the supernova.Comment: 28 pages, 11 figure

Neutrino parameters from matter effects in PeeP_{ee} at long baselines

We show that the earth matter effects in the ${\rm {\nu_e \to \nu_e}}$ survival probability can be used to cleanly determine the third leptonic mixing angle $\theta_{13}$ and the sign of the atmospheric neutrino mass squared difference, $\Delta m^2_{31}$, using a $\beta$-beam as a $\nu_e$ source.Comment: 4 pages, 4 eps figures; comments and references added, to appear in Phys. Rev.

A review: Solar cell current scenario and future trends

In recent years solar cell technology has achieved tremendous growth as sustainable source of energy. In last few years photovoltaic industries have emerged with an annual growth of 40%.Solar cells are renewable pollution free source of electrical energy which can easily replace traditional fossil fuels. In this article we have reviewed the previous and current status of various generations of solar cells and discussed about their future trends and aspects.&nbsp