31 research outputs found
Mental health Policy and Programs in Israel: Trends and Problems of a Developing System
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
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 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
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
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
We propose helical trilayer graphene (HTG), a helical structure featuring
identical rotation angles 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 is broken, giving rise to flat topological bands carrying
valley-Chern numbers . These bands feature near-ideal quantum
geometry and are isolated from remote bands by a large gap
meV, making HTG a promising platform for
experimental realization of correlated topological states such as integer and
fractional quantum anomalous Hall states in and bands
Probing dynamics and pinning of single vortices in superconductors at nanometer scales
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
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 -inversion symmetry
() 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
-symmetric, surprisingly we observe clear signatures of topological
bands. At a magic angle , we uncover a
robust phase diagram of correlated and magnetic states using magnetotransport
measurements. Lattice relaxation leads to large periodic domains in which
is broken on the moir\'e scale. Each domain harbors flat topological
bands with valley-contrasting Chern numbers . We find correlated
states at integer electron fillings per moir\'e unit cell and
fractional fillings with the AHE arising at and .
At , a time-reversal symmetric phase appears beyond a critical electric
displacement field, indicating a topological phase transition. Finally,
hysteresis upon sweeping 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