130 research outputs found
Out-of-plane magnetic domain structure in a thin film of La0.67Sr0.33MnO3 on SrTiO3 (001) observed by magnetic force microscopy
The room temperature out-of-plane magnetization of epitaxial thin films of La0.67Sr0.33MnO3 on SrTiO3 (001) has been investigated with magnetic force microscopy, using magnetic tips with very small coercivity, relative to the film. A clear magnetic pattern in the form of a checkerboard, with domain dimensions of a few hundred nanometers, was found for the thin, coherently strained films, which is approximately aligned along the maximum strain [110] and [1[overline 1]0] directions in the film. With increasing in-plane applied magnetic field, the magnetic contrast reduces, reflecting the rotation of the magnetization vector into the plane of the film. This process is reversible with the field. The out-of-plane magnetic pattern is not sensitive to rotation of the in-plane field. We attribute the observed out-of-plane magnetization component to an out-of-plane magnetic anisotropy, which is a remainder of the [111] magnetic easy axis in bulk La0.67Sr0.33MnO3 single crystal
Orbital reconstruction and two-dimensional electron gas at the LaAlO3/SrTiO3 interface
Conventional two-dimensional electron gases are realized by engineering the
interfaces between semiconducting compounds. In 2004, Ohtomo and Hwang
discovered that an electron gas can be also realized at the interface between
large gap insulators made of transition metal oxides [1]. This finding has
generated considerable efforts to clarify the underlying microscopic mechanism.
Of particular interest is the LaAlO3/SrTiO3 system, because it features
especially striking properties. High carrier mobility [1], electric field
tuneable superconductivity [2] and magnetic effects [3], have been found. Here
we show that an orbital reconstruction is underlying the generation of the
electron gas at the LaAlO3/SrTiO3 n-type interface. Our results are based on
extensive investigations of the electronic properties and of the orbital
structure of the interface using X-ray Absorption Spectroscopy. In particular
we find that the degeneracy of the Ti 3d states is fully removed, and that the
Ti 3dxy levels become the first available states for conducting electrons.Comment: 12 pages, 3 figure
Photodoping and in-gap interface states across the metal-insulator transition in LaAlO3/SrTiO3 heterostructures
By using scanning tunneling microscopy/spectroscopy we show that the interface between LaAlO3 and SrTiO3 band insulators is characterized by in-gap interface states. These features were observed in insulating as well as conducting LaAlO3/SrTiO3 bilayers. The data show how the interface density of states evolves across the insulating to metal transition, demonstrating that nanoscale electronic inhomogeneities in the system are induced by spatially localized electrons
A novel system to map protein interactions reveals evolutionarily conserved immune evasion pathways on transmissible cancers
Around 40% of humans and Tasmanian devils (Sarcophilus harrisii) develop cancer in their lifetime, compared to less than 10% for most species. In addition, devils are affected by two of the three known transmissible cancers in mammals. Immune checkpoint immunotherapy has transformed human medicine, but a lack of species-specific reagents has limited checkpoint immunology in most species. We developed a cut-and-paste reagent development system and used the fluorescent fusion protein system to show that immune checkpoint interactions are conserved across 160,000,000 years of evolution, CD200 is highly expressed on transmissible tumor cells, and coexpression of CD200R1 can block CD200 surface expression. The systemâs versatility across species was demonstrated by fusing a fluorescent reporter to a camelid-derived nanobody that binds human programmed death ligand 1. The evolutionarily conserved pathways suggest that naturally occurring cancers in devils and other species can be used to advance our understanding of cancer and immunological tolerance.</p
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Energy and symmetry of dd excitations in undoped layered cuprates measured By Cu L3 resonant inelastic x-ray scattering
We measured the high-resolution Cu L3 edge resonant inelastic x-ray scattering (RIXS) of undoped cuprates La2CuO4, Sr2CuO2Cl2, CaCuO2 and NdBa 2Cu3O6. The dominant spectral features were assigned to dd excitations and we extensively studied their polarization and scattering geometry dependence. In a pure ionic picture, we calculated the theoretical cross sections for those excitations and used these to fit the experimental data with excellent agreement. By doing so, we were able to determine the energy and symmetry of Cu-3d states for the four systems with unprecedented accuracy and confidence. The values of the effective parameters could be obtained for the singleion crystal field model but not for a simple two-dimensional cluster model. The firm experimental assessment of dd excitation energies carries important consequences for the physics of high-Tc superconductors. On the one hand, we found that the minimum energy of orbital excitation is always â„ 1.4 eV, i.e. well above the mid-infrared spectral range, which leaves to magnetic excitations (up to 300 meV) a major role in Cooper pairing in cuprates. On the other hand, it has become possible to study quantitatively the effective influence of dd excitations on the superconducting gap in cuprates
Phenomenology of the Lense-Thirring effect in the Solar System
Recent years have seen increasing efforts to directly measure some aspects of
the general relativistic gravitomagnetic interaction in several astronomical
scenarios in the solar system. After briefly overviewing the concept of
gravitomagnetism from a theoretical point of view, we review the performed or
proposed attempts to detect the Lense-Thirring effect affecting the orbital
motions of natural and artificial bodies in the gravitational fields of the
Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of
the impact of several sources of systematic uncertainties of dynamical origin
to realistically elucidate the present and future perspectives in directly
measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in
Astrophysics and Space Science (ApSS). Some uncited references in the text
now correctly quoted. One reference added. A footnote adde
Role of chaos for the validity of statistical mechanics laws: diffusion and conduction
Several years after the pioneering work by Fermi Pasta and Ulam, fundamental
questions about the link between dynamical and statistical properties remain
still open in modern statistical mechanics. Particularly controversial is the
role of deterministic chaos for the validity and consistency of statistical
approaches. This contribution reexamines such a debated issue taking
inspiration from the problem of diffusion and heat conduction in deterministic
systems. Is microscopic chaos a necessary ingredient to observe such
macroscopic phenomena?Comment: Latex, 27 pages, 10 eps-figures. Proceedings of the Conference "FPU
50 years since" Rome 7-8 May 200
SOIL ORGANIC CARBON, CARBON STOCK AND THEIR RELATIONSHIPS TO PHYSICAL ATTRIBUTES UNDER FOREST SOILS IN CENTRAL AMAZONIA
Large-scale ICU data sharing for global collaboration: the first 1633 critically ill COVID-19 patients in the Dutch Data Warehouse
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