31 research outputs found

    Mental health Policy and Programs in Israel: Trends and Problems of a Developing System

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    Israel has an ancient history blended together with a relatively brief independent identity. An introductory section provides a backdrop for understanding mental health policies and programs in the context of the cultural and historical background of Israel\u27s people. The second section portrays the nature of the mental health delivery system. The final section focuses on three interrelated issues: the limited development of community mental health services, the dominance of the mental hospital in the provision of mental health services, and the medicalization of mental health services

    Electrically tunable multi-terminal SQUID-on-tip

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    We present a new nanoscale superconducting quantum interference device (SQUID) whose interference pattern can be shifted electrically in-situ. The device consists of a nanoscale four-terminal/four-junction SQUID fabricated at the apex of a sharp pipette using a self-aligned three-step deposition of Pb. In contrast to conventional two-terminal/two-junction SQUIDs that display optimal sensitivity when flux biased to about a quarter of the flux quantum, the additional terminals and junctions allow optimal sensitivity at arbitrary applied flux, thus eliminating the magnetic field "blind spots". We demonstrate spin sensitivity of 5 to 8 μB/Hz1/2\mu_B/\text{Hz}^{1/2} over a continuous field range of 0 to 0.5 T, with promising applications for nanoscale scanning magnetic imaging

    Nanoscale imaging of equilibrium quantum Hall edge currents and of the magnetic monopole response in graphene

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    The recently predicted topological magnetoelectric effect and the response to an electric charge that mimics an induced mirror magnetic monopole are fundamental attributes of topological states of matter with broken time reversal symmetry. Using a SQUID-on-tip, acting simultaneously as a tunable scanning electric charge and as ultrasensitive nanoscale magnetometer, we induce and directly image the microscopic currents generating the magnetic monopole response in a graphene quantum Hall electron system. We find a rich and complex nonlinear behavior governed by coexistence of topological and nontopological equilibrium currents that is not captured by the monopole models. Furthermore, by utilizing a tuning fork that induces nanoscale vibrations of the SQUID-on-tip, we directly image the equilibrium currents of individual quantum Hall edge states for the first time. We reveal that the edge states that are commonly assumed to carry only a chiral downstream current, in fact carry a pair of counterpropagating currents, in which the topological downstream current in the incompressible region is always counterbalanced by heretofore unobserved nontopological upstream current flowing in the adjacent compressible region. The intricate patterns of the counterpropagating equilibrium-state orbital currents provide new insights into the microscopic origins of the topological and nontopological charge and energy flow in quantum Hall systems

    Imaging resonant dissipation from individual atomic defects in graphene

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    Conversion of electric current into heat involves microscopic processes that operate on nanometer length-scales and release minute amounts of power. While central to our understanding of the electrical properties of materials, individual mediators of energy dissipation have so far eluded direct observation. Using scanning nano-thermometry with sub-micro K sensitivity we visualize and control phonon emission from individual atomic defects in graphene. The inferred electron-phonon 'cooling power spectrum' exhibits sharp peaks when the Fermi level comes into resonance with electronic quasi-bound states at such defects, a hitherto uncharted process. Rare in the bulk but abundant at graphene's edges, switchable atomic-scale phonon emitters define the dominant dissipation mechanism. Our work offers new insights for addressing key materials challenges in modern electronics and engineering dissipation at the nanoscale

    Magic-angle helical trilayer graphene

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    We propose helical trilayer graphene (HTG), a helical structure featuring identical rotation angles θ1.5\theta\approx 1.5^\circ between three consecutive layers of graphene, as a unique and experimentally accessible platform for realizing exotic correlated topological states of matter. While nominally forming a supermoir\'e (or moir\'e-of-moir\'e) structure, we show that HTG locally relaxes into large regions of a periodic single-moir\'e structure in which C2zC_{2z} is broken, giving rise to flat topological bands carrying valley-Chern numbers C=±(1,2)C=\pm(1,-2). These bands feature near-ideal quantum geometry and are isolated from remote bands by a large gap Egap100E_{\mathrm{gap}}\sim 100 meV, making HTG a promising platform for experimental realization of correlated topological states such as integer and fractional quantum anomalous Hall states in C=1C=1 and 22 bands

    Probing dynamics and pinning of single vortices in superconductors at nanometer scales

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    The dynamics of quantized magnetic vortices and their pinning by materials defects determine electromagnetic properties of superconductors, particularly their ability to carry non-dissipative currents. Despite recent advances in the understanding of the complex physics of vortex matter, the behavior of vortices driven by current through a multi-scale potential of the actual materials defects is still not well understood, mostly due to the scarcity of appropriate experimental tools capable of tracing vortex trajectories on nanometer scales. Using a novel scanning superconducting quantum interference microscope we report here an investigation of controlled dynamics of vortices in lead films with sub-Angstrom spatial resolution and unprecedented sensitivity. We measured, for the first time, the fundamental dependence of the elementary pinning force of multiple defects on the vortex displacement, revealing a far more complex behavior than has previously been recognized, including striking spring softening and broken-spring depinning, as well as spontaneous hysteretic switching between cellular vortex trajectories. Our results indicate the importance of thermal fluctuations even at 4.2 K and of the vital role of ripples in the pinning potential, giving new insights into the mechanisms of magnetic relaxation and electromagnetic response of superconductors.Comment: 15 pages and 5 figures (main text) + 15 pages and 11 figures (supplementary material

    Helical trilayer graphene: a moir\'e platform for strongly-interacting topological bands

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    Quantum geometry of electronic wavefunctions results in fascinating topological phenomena. A prominent example is the intrinsic anomalous Hall effect (AHE) in which a Hall voltage arises in the absence of an applied magnetic field. The AHE requires a coexistence of Berry curvature and spontaneous time-reversal symmetry breaking. These conditions can be realized in two-dimensional moir\'e systems with broken xyxy-inversion symmetry (C2zC_{2z}) that host flat electronic bands. Here, we explore helical trilayer graphene (HTG), three graphene layers twisted sequentially by the same angle forming two misoriented moir\'e patterns. Although HTG is globally C2zC_{2z}-symmetric, surprisingly we observe clear signatures of topological bands. At a magic angle θm1.8\theta_\mathrm{m}\approx 1.8^\circ, we uncover a robust phase diagram of correlated and magnetic states using magnetotransport measurements. Lattice relaxation leads to large periodic domains in which C2zC_{2z} is broken on the moir\'e scale. Each domain harbors flat topological bands with valley-contrasting Chern numbers ±(1,2)\pm(1,-2). We find correlated states at integer electron fillings per moir\'e unit cell ν=1,2,3\nu=1,2,3 and fractional fillings 2/3,7/22/3,7/2 with the AHE arising at ν=1,3\nu=1,3 and 2/3,7/22/3,7/2. At ν=1\nu=1, a time-reversal symmetric phase appears beyond a critical electric displacement field, indicating a topological phase transition. Finally, hysteresis upon sweeping ν\nu points to first-order phase transitions across a spatial mosaic of Chern domains separated by a network of topological gapless edge states. We establish HTG as an important platform that realizes ideal conditions for exploring strongly interacting topological phases and, due to its emergent moir\'e-scale symmetries, demonstrates a novel way to engineer topology
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