52 research outputs found
Nanoscale Electrostatic Control of Oxide Interfaces
We develop a robust and versatile platform to define nanostructures at oxide
interfaces via patterned top gates. Using LaAlO/SrTiO as a model
system, we demonstrate controllable electrostatic confinement of electrons to
nanoscale regions in the conducting interface. The excellent gate response,
ultra-low leakage currents, and long term stability of these gates allow us to
perform a variety of studies in different device geometries from room
temperature down to 50 mK. Using a split-gate device we demonstrate the
formation of a narrow conducting channel whose width can be controllably
reduced via the application of appropriate gate voltages. We also show that a
single narrow gate can be used to induce locally a superconducting to
insulating transition. Furthermore, in the superconducting regime we see
indications of a gate-voltage controlled Josephson effect.Comment: Version after peer review; includes additional data on
superconductivit
Superconducting quantum point contact with split gates in the two dimensional LaAlO3/SrTiO3 superfluid
One of the hallmark experiments of quantum transport is the observation of
the quantized resistance in a point contact formed with split gates in
GaAs/AlGaAs heterostructures. Being carried out on a single material, they
represent in an ideal manner equilibrium reservoirs which are connected only
through a few electron mode channel with certain transmission coefficients. It
has been a long standing goal to achieve similar experimental conditions also
in superconductors, only reached in atomic scale mechanically tunable break
junctions of conventional superconducting metals, but here the Fermi wavelength
is so short that it leads to a mixing of quantum transport with atomic orbital
physics. Here we demonstrate for the first time the formation of a
superconducting quantum point contact (SQPC) with split gate technology in a
superconductor, utilizing the unique gate tunability of the two dimensional
superfluid at the LaAlO3/SrTiO3 (LAO/STO) interface. When the constriction is
tuned through the action of metallic split gates we identify three regimes of
transport: (i) SQPC for which the supercurrent is carried only by a few quantum
transport channels. (ii) Superconducting island strongly coupled to the
equilibrium reservoirs. (iii) Charge island with a discrete spectrum weakly
coupled to the reservoirs. Our experiments demonstrate the feasibility of a new
generation of mesoscopic all-superconductor quantum transport devices.Comment: 18 page
Giant Dipole Resonance Width in near-Sn Nuclei at Low Temperature and High Angular Momentum
High energy gamma-rays in coincidence with low energy yrast gamma-rays have
been measured from 113Sb, at excitation energies of 109 and 122 MeV, formed by
bombarding 20Ne on 93Nb at projectile energies of 145 and 160 MeV respectively
to study the role of angular momentum (J) and temperature (T) over Giant Dipole
Resonance (GDR) width. The maximum populated angular momenta for fusion were
67hbar and 73hbar respectively for the above-mentioned beam energies. The high
energy photons were detected using a Large Area Modular BaF2 Detector Array
(LAMBDA) along with a 24-element multiplicity filter. After pre-equilibrium
corrections, the excitation energy E* was averaged over the decay steps of the
compound nucleus (CN). The average values of temperature, angular momentum, CN
mass etc. have been calculated by the statistical model code CASCADE. Using
those average values, results show the systematic increase of GDR width with T
which is consistent with Kusnezov parametrization and the Thermal Shape
Fluctuation Model. The rise of GDR width with temperature also supports the
assumptions of adiabatic coupling in the Thermal Shape Fluctuation Model. But
the GDR widths and corresponding reduced plots with J are not consistent with
the theoretical model at high spins.Comment: 19 pages, 10 figures, Submitted to Physics Review
On Late Time Tails in an Extreme Reissner-Nordstr\"om Black Hole: Frequency Domain Analysis
In this brief note, we revisit the study of the leading order late time decay
tails of massless scalar perturbations outside an extreme Reissner-Nordstr\"om
black hole. Previous authors have analysed this problem in the time domain; we
analyse the problem in the frequency domain. We first consider initial
perturbations with generic regular behaviour across the horizon on
characteristic surfaces. For this set-up, we reproduce some of the previous
results of Sela [arXiv:1510.06169] using Fourier methods. Next, we consider
related initial data on t=\mbox{const} hypersurfaces, and present decay
results at timelike infinity, near future null infinity, and near the future
horizon. Along the way, using the inversion symmetry of the
extreme Reissner-Nordstr\"om spacetime, we relate the higher multipole Aretakis
and Newman-Penrose constants for a massless scalar in this background.Comment: 22 pages; 2 figure
Flux-tunable Josephson Effect in a Four-Terminal Junction
We study a phase-tunable four-terminal Josephson junction formed in an InSbAs
two-dimensional electron gas proximitized by aluminum. By embedding the two
pairs of junction terminals in asymmetric DC SQUIDs we can control the
superconducting phase difference across each pair, thereby gaining information
about their current-phase relation. Using a current-bias line to locally
control the magnetic flux through one SQUID, we measure a nonlocal Josephson
effect, whereby the current-phase relation across two terminals in the junction
is strongly dependent on the superconducting phase difference across two
completely different terminals. In particular, each pair behaves as a
-junction with a phase offset tuned by the phase difference across the
other junction terminals. Lastly, we demonstrate that the behavior of an array
of two-terminal junctions replicates most features of the current-phase
relation of different multiterminal junctions. This highlights that these
signatures alone are not sufficient evidence of true multiterminal Josephson
effects arising from hybridization of Andreev bound states in the junction.Comment: 13 pages, 8 figure
Onset of deformation at in Bi nuclei
The high spin states in Bi has been studied by -ray
spectroscopic method using the Ta(Ne, 6n) fusion evaporation
reaction at 130 MeV. The coincidence data were taken using an
array of 8 clover HPGe detectors. The spin and parity assignments of the
excited states have been made from the measured directional correlation from
oriented states (DCO) ratios and integrated polarization asymmetry (IPDCO)
ratios. The results show, for the first time, the evidence of a rotational like
band based on a 13/2 band head in this nucleus, indicating the onset of
deformation at neutron number for the Bismuth isotopes. The results
obtained were found to be consistent with the prediction of the total Routhian
surface calculations using Woods Saxon potential. The same calculations also
predict a change in shape from oblate to triaxial in Bi at high
rotational frequency
Unilateral absence of the lunate sulcus: an anatomical perspective.
The present study examines the gross anatomical features of anomalous lunate sulcus detected incidentally in a cadaveric brain and discusses its clinical importance. The absence of lunate sulcus was carefully studied in a dissected brain specimen. The absence of lunate sulcus was observed unilaterally on the right side of a cadaveric brain specimen. The lunate sulcus was clearly appreciated on the left side whilst on the right side it was absent. The right hemisphere of the cerebellum was also bigger in size as compared to the left. The absence of lunate sulcus is a rare finding, which may be detected incidentally. The anatomical knowledge of the lunate sulcus may be important for neurosurgeons operating on the occipital lobe and the radiologists interpreting CT scan
C CA AS SE E R RE EP PO OR RT T Unilateral absence of the lunate sulcus: an anatomical perspective
Abstract The present study examines the gross anatomical features of anomalous lunate sulcus detected incidentally in a cadaveric brain and discusses its clinical importance. The absence of lunate sulcus was carefully studied in a dissected brain specimen. The absence of lunate sulcus was observed unilaterally on the right side of a cadaveric brain specimen. The lunate sulcus was clearly appreciated on the left side whilst on the right side it was absent. The right hemisphere of the cerebellum was also bigger in size as compared to the left. The absence of lunate sulcus is a rare finding, which may be detected incidentally. The anatomical knowledge of the lunate sulcus may be important for neurosurgeons operating on the occipital lobe and the radiologists interpreting CT scan
The Role of Caregivers in the Management of Alzheimer’s Disease : Examples from Asian Countries
The demographic profile of the Asian population is rapidly changing, with a fast increasing ageing population, owing to an increase in longevity and a decreasing birth rate. Moreover, due to improved medical facilities and the increased aged population, Alzheimer’s disease (AD) is fast emerging as a major health problem in many Asian countries. As curative treatment for AD is still elusive, care giving is an important component of the management of AD. While Western countries have recognised this issue, besides highly industrialized Japan, the Asian initiative has been relatively slow. This article aims to address issues involved in caregiving in AD in some Asian countries.
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