Boaz Almog

Kondo-like behavior near the metal-to-insulator transition of nanoscale granular aluminum

We show that the normal state transport properties of nano-scale granular Aluminum films, near the metal to insulator transition, present striking similarities with those of Kondo systems. Those include a negative magneto-resistance, a minimum of resistance R at a temperature Tm in metallic films, a logarithmic rise at low temperatures and a negative curvature of R(T) at high temperatures. These normal state properties are interpreted in terms of spin-flip scattering of conduction electrons by local magnetic moments, possibly located at the metal/oxide interfaces. Their co-existence with the enhanced superconductivity seen in these films is discussed.

Mott transition in granular aluminum

A Mott transition in granular Al films is observed by probing the increase of the spin-flip scattering rate of conduction electrons as the nanosize metallic grains are being progressively decoupled. The presence of free spins in granular Al films is directly demonstrated by

Observation of Andreev–Saint-James reflections in nano-scale planar superconductor to ferromagnet contacts

\ensuremath{\mu}\mathrm{SR}

Homogenous Crack‐Free Large Size YBCO/YSZ/Sapphire Films for Application

measurements. Analysis of the magnetoresistance in terms of an effective Fermi energy shows that it becomes of the order of the grains electrostatic charging energy at a room temperature resistivity

Coexistence of a triplet nodal order parameter and a singlet order parameter at the interfaces of ferromagnet/superconductor Co/CoO/In junctions

{\ensuremath{\rho}}_{300\phantom{\rule{4pt}{0ex}}\mathrm{K}}\ensuremath{\approx}50000\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\ensuremath{\Omega}\phantom{\rule{4pt}{0ex}}\mathrm{cm}

Temperature dependance of the tunneling density of states in sub-micron planar metal/oxide/graphene junctions

, at which a metal to insulator transition is known to exist. As this transition is approached the magnetoresistance exhibits a heavy-fermion-like behavior, consistent with an increased electron effective mass.

Current-driven transitions in ferromagnetic/insulator/superconductor narrow stripes

We fabricated nanoscale ferromagnetic (F) Nickel/superconducting (S) indium junctions which show that spin polarization effects on the contact conductance can be observed in a planar geometry. The data demonstrate that the Andreev–Saint-James [Sov. Phys. JETP 19, 1228 (1964) and J. Phys. (Paris) 25, 899 (1964)] electron-hole reflections at the F∕S interface, which are sensitive to the polarization of the F side, dominate the conductance of the contact at low bias. The simplicity of fabrication makes these junctions appealing for use in multiterminal SF structures.

Characterization of large size YBa2Cu3O7−δ films using magnetic field penetration

YBa2Cu3O7−δ (YBCO) films grown on Sapphire are highly suitable for applications. The production of large size (2–3″) homogeneous, thick (d ⩾ 600nm) films of high quality is of major importance. We report the growth of such films using a buffer layer of Yttrium‐stabilized ZrO2(YSZ). The films are highly homogeneous and show excellent mechanical properties. They exhibit no sign of cracking even after many thermal cycles. Their critical thickness exceeds 1000nm. However, because of the large lattice mismatch there is a decrease in the electric properties(increases Rs, decreases jc).

Long-range odd triplet order parameter with equal spin pairing in diffusive Co/In contacts

Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, 69978 Tel-Aviv, Israel(Dated: July 13, 2011)We present differential conductance measurements of Cobalt / Cobalt-Oxide / Indium planarjunctions, 500nm x 500nm in size. The junctions span a wide range of barriers, from very low to atunnel barrier. The characteristic conductance of all the junctions show a V-shape structure at lowbias instead of the U-shape characteristic of a s-wave order parameter. The bias of the conductancepeaks is, for all junctions, larger than the gap of indium. Both properties exclude pure s-wavepairing. The data is well fitted by a model that assumes the coexistence of s-wave singlet andequal spin p-wave triplet fluids. We find that the values of the s-wave and p-wave gaps follow theBCS temperature dependance and that the amplitude of the s-wave fluid increases with the barrierstrength.I. INTRODUCTION

High temperature superconductive films and methods of making them

We present the tunneling measurements of sub-micron metal/insulator/graphene planar tunnel junctions up to room temperature. We observe a gate independent gap, as previously observed only by low temperature STM [Y. Zhang et al., Nat. Phys. 4, 627 (2008)]. No gap appears at temperatures above 150 K, which is four times smaller than the theoretically expected Tc, from the accepted mean field model [T. O. Wehling et al., Phys. Rev. Lett. 101, 216803 (2008)]. We show that taking into account an additional vibrational effect of out-of-plane phonon soft modes the gap may disappear from the measurements at temperatures much lower than the calculated Tc.