397 research outputs found
Field-effect control of superconductivity and Rashba spin-orbit coupling in top-gated LaAlO3/SrTiO3 devices
The recent development in the fabrication of artificial oxide
heterostructures opens new avenues in the field of quantum materials by
enabling the manipulation of the charge, spin and orbital degrees of freedom.
In this context, the discovery of two-dimensional electron gases (2-DEGs) at
LAlO3/SrTiO3 interfaces, which exhibit both superconductivity and strong Rashba
spin-orbit coupling (SOC), represents a major breakthrough. Here, we report on
the realisation of a field-effect LaAlO3/SrTiO3 device, whose physical
properties, including superconductivity and SOC, can be tuned over a wide range
by a top-gate voltage. We derive a phase diagram, which emphasises a
field-effect-induced superconductor-to-insulator quantum phase transition.
Magneto-transport measurements indicate that the Rashba coupling constant
increases linearly with electrostatic doping. Our results pave the way for the
realisation of mesoscopic devices, where these two properties can be
manipulated on a local scale by means of top-gates
Temporal resolution deficits in the visual fields of MS patients
AbstractWe assessed the relationship between temporal resolution and MS-induced neuropathy. A diagnostic strategy comprising assessments of temporal resolution at 16 points in the extra-foveal visual field up to 12° from the fovea was first compared with foveal temporal resolution and with a standard VEP procedure in the same MS patients. At the group level, foveal temporal resolution was less sensitive to demyelination than the 16-point diagnostic strategy, the detection rate of which was comparable to that of the VEP procedure. Cross-sensitivity of the VEP and the 16-point diagnostic procedure was low. Subsequently, the average severity of MS-induced temporal resolution deficits was studied at three retinal loci of the same size but different eccentricities. Foveal deficits were not significantly greater than more peripheral deficits within the central 12°
Oblique basin inversion and strain partitioning in back-arc context: example from the Moroccan Alboran Margin (Western Mediterranean)
EUROPEAN GEOPHYSICAL UNIO
Quartic scaling of sound attenuation with frequency in vitreous silica
Several theoretical approaches to disordered media predict that acoustic
waves should undergo a quartic increase in their attenuation coefficient with
increasing frequency in the sub-terahertz region. Such Rayleigh-type scattering
would be related to the anomalous low-temperature plateau in the thermal
conductivity and to the so-called boson peak, i.e. an excess of vibrational
modes above the Debye density of states at around 1 THz. Brillouin scattering
of light allows the measurement of sound absorption and velocity dispersion up
to about 0.1 THz while inelastic x-ray scattering is limited to frequencies
larger than about 1 THz. We take advantage of the advent of ultrafast optical
techniques to explore the acoustical properties of amorphous SiO2 layers in the
difficult but crucial frequency region within this gap. A quartic scaling law
with frequency is clearly revealed between 0.2 and 0.9 THz, which is further
shown to be independent of temperature. This strongly damped regime is
accompanied by a decrease in the sound velocity already starting from about 0.5
THz, in line with theories. Our study assists to clarify the anomalous
acoustical properties in glasses at frequencies entering the boson peak region.Comment: 4 figures, 11 page
Orbifold projection in supersymmetric QCD at N_f\leq N_c
Supersymmetric orbifold projection of N=1 SQCD with relatively small number
of flavors (not larger than the number of colors) is considered. The purpose is
to check whether orbifolding commutes with the infrared limit. On the one hand,
one considers the orbifold projection of SQCD and obtains the low-energy
description of the resulting theory. On the other hand, one starts with the
low-energy effective theory of the original SQCD, and only then perfoms
orbifolding. It is shown that at finite N_c the two low-energy theories
obtained in these ways are different. However, in the case of stabilized
run-away vacuum these two theories are shown to coincide in the large N_c
limit. In the case of quantum modified moduli space, topological solitons
carrying baryonic charges are present in the orbifolded low-energy theory.
These solitons may restore the correspondence between the two theories provided
that the soliton mass tends to zero in the large N_c limit.Comment: 10 pages; misprint corrected, reference adde
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