3,134 research outputs found
Surface composition of BaTiO3/SrTiO3(001) films grown by atomic oxygen plasma assisted molecular beam epitaxy
We have investigated the growth of BaTiO3 thin films deposited on pure and 1%
Nb-doped SrTiO3(001) single crystals using atomic oxygen assisted molecular
beam epitaxy (AO-MBE) and dedicated Ba and Ti Knudsen cells. Thicknesses up to
30 nm were investigated for various layer compositions. We demonstrate 2D
growth and epitaxial single crystalline BaTiO3 layers up to 10 nm before
additional 3D features appear; lattice parameter relaxation occurs during the
first few nanometers and is completed at {\guillemotright}10 nm. The presence
of a Ba oxide rich top layer that probably favors 2D growth is evidenced for
well crystallized layers. We show that the Ba oxide rich top layer can be
removed by chemical etching. The present work stresses the importance of
stoichiometry and surface composition of BaTiO3 layers, especially in view of
their integration in devices.Comment: In press in J. Appl. Phy
Structural and magnetic properties of CoPt mixed clusters
In this present work, we report a structural and magnetic study of mixed
Co58Pt42 clusters. MgO, Nb and Si matrix can be used to embed clusters,
avoiding any magnetic interactions between particles. Transmission Electron
Microscopy (TEM) observations show that Co58Pt42 supported isolated clusters
are about 2nm in diameter and crystallized in the A1 fcc chemically disordered
phase. Grazing Incidence Small Angle X-ray Scattering (GISAXS) and Grazing
Incidence Wide Angle X-ray Scattering (GIWAXS) reveal that buried clusters
conserve these properties, interaction with matrix atoms being limited to their
first atomic layers. Considering that 60% of particle atoms are located at
surface, this interactions leads to a drastic change in magnetic properties
which were investigated with conventional magnetometry and X-Ray Magnetic
Circular Dichro\"{i}sm (XMCD). Magnetization and blocking temperature are
weaker for clusters embedded in Nb than in MgO, and totally vanish in silicon
as silicides are formed. Magnetic volume of clusters embedded in MgO is close
to the crystallized volume determined by GIWAXS experiments. Cluster can be
seen as a pure ferromagnetic CoPt crystallized core surrounded by a
cluster-matrix mixed shell. The outer shell plays a predominant role in
magnetic properties, especially for clusters embedded in niobium which have a
blocking temperature 3 times smaller than clusters embedded in MgO
Electronic and magnetic properties of metallic phases under coexisting short-range interaction and diagonal disorder
We study a three-dimensional Anderson-Hubbard model under the coexistence of
short-range interaction and diagonal disorder within the Hartree-Fock
approximation. We show that the density of states at the Fermi energy is
suppressed in the metallic phases near the metal-insulator transition as a
proximity effect of the soft Hubbard gap in the insulating phases. The
transition to the insulator is characterized by a vanishing DOS in contrast to
formation of a quasiparticle peak at the Fermi energy obtained by the dynamical
mean field theory in pure systems. Furthermore, we show that there exist frozen
spin moments in the paramagnetic metal.Comment: 4 pages, 2 figures, published versio
New oral anticoagulants and their reversal agents
Atrial fibrillation is a commonly encountered pathology in medical practice, and its prevalence has shown a continuous rise over the past years. Atrial fibrillation has a significant impact on patients\u27 quality of life, not only due to the standard anticoagulant treatment with vitamin K antagonists that require close monitoring and dose adjustment, but also due to the fragile equilibrium between hemorrhagic and thrombotic risks. The introduction of new oral anticoagulants (NOACs) in the treatment guidelines for atrial fibrillation has improved the quality of life, as NOACs do not require close monitoring or dose adjustments. However, even if the safety profile of the NOACs regarding the hemorrhagic risk is superior to vitamin K antagonists, the problem raised by an unexpected hemorrhage (e.g. severe hemorrhage after an accident) and the need for efficient hemostasis in a chronic anticoagulated patient has remained unsolved. To find a solution for this problem, reversal agents for NOACs have been developed and tested, and two of them, idarucizumab and andexanet-alpha, have already been approved by the FDA, thus making NOACs increasingly appealing as a choice of anticoagulation treatment
Stability of Unconventional Superconductivity on Surfaces of Topological Insulators
Superconductivity on the surface of topological insulators is known to be
anisotropic and unconventional in that the symmetry is the mixture of s-wave
and nodeless p-wave component. In contrast to Anderson's theorem for the
insensitivity of the s-wave superconducting critical temperature to the
nonmagnetic (time-reversal symmetric (TRS)) impurities, anisotropic
superconductors including nodeless p-wave one are in general fragile even with
small concentration of the TRS impurities. By employing the Abrikosov-Gor'kov
theory, we clarify that this type of unconventional superconductivity emergent
on the surface state of the strong topological insulators robustly survive
against TRS impurities
Much Ado about Zeros: The Luttinger Surface and Mottness
We prove that the Mott insulating state is characterized by a divergence of
the electron self energy at well-defined values of momenta in the first
Brillouin zone. When particle-hole symmetry is present, the divergence obtains
at the momenta of the Fermi surface for the corresponding non-interacting
system. Such a divergence gives rise to a surface of zeros (the Luttinger
surface) of the single-particle Green function and offers a single unifying
principle of Mottness from which pseudogap phenomena, spectral weight transfer,
and broad spectral features emerge in doped Mott insulators. We also show that
only when particle-hole symmetry is present does the volume of the zero surface
equal the particle density. We identify that the general breakdown of
Luttinger's theorem in a Mott insulator arises from the breakdown of a
perturbative expansion for the self energy in the single-particle Green
function around the non-interacting limit. A modified version of Luttinger's
theorem is derived for special cases.Comment: New version proves explicitly that only when particle-hole symmetry
is present does the volume of the surface of zeros equal the particle density
thereby generalising recent perturbative argument
Impurity Effects on Superconductivity on Surfaces of Topological Insulators
A two-dimensional superconductor (SC) on surfaces of topological insulators
(TIs) is a mixture of s-wave and helical p-wave components when induced by
s-wave interactions, since spin and momentum are correlated. On the basis of
the Abrikosov-Gor'kov theory, we reveal that unconventional SCs on the surfaces
of TIs are stable against time-reversal symmetric (TRS) impurities within a
region of small impurity concentration. Moreover, we analyze the stability of
the SC on the surfaces of TIs against impurities beyond the perturbation theory
by solving the real-space Bogoliubov-de Gennes equation for an effective
tight-binding model of a TI. We find that the SC is stable against strong TRS
impurities. The behaviors of bound states around an impurity suggest that the
SC on the surfaces of TIs is not a topological SC.Comment: 17 pages, 14 figures, to appear in J. Phys. Soc. Jp
Approaches and Directions for the Physiotherapeutic Management of Patients with “Duchenne” Muscular Dystrophy
Duchenne muscular dystrophy (DMD) affects cardiac and skeletal muscles but represents a condition that causes numerous secondary pathologies. Although there is no curative treatment available, multidisciplinary approaches, centered on the needs of the patient, improve the quality and duration of life. Therapies such as physiotherapy, occupational therapy, physical activities, and respiratory physiotherapy, but also the management of cardiac, osteo-muscular, and neuro-psychiatric manifestations, are continuously developing, (as new data becomes available) and are the key to DMD management today. These multidisciplinary approaches can lead to good long-term outcomes by helping patients with muscular dystrophy reduce muscle damage, early detect and treat heart failure, and manage cognitive impairment as best they can
Density Induced Interchange of Anisotropy Axes at Half-Filled High Landau Levels
We observe density induced 90 rotations of the anisotropy axes in
transport measurements at half-filled high Landau levels in the two dimensional
electron system, where stripe states are proposed (=9/2, 11/2, etc). Using
a field effect transistor, we find the transition density to be
cm at =9/2. Hysteresis is observed in the
vicinity of the transition. We construct a phase boundary in the filling
factor-magnetic field plane in the regime . An in-plane magnetic
field applied along either anisotropy axis always stabilizes the low density
orientation of the stripes.Comment: 1 revtex file, 3 eps figure
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