L. Braicovich

Long-Range Incommensurate Charge Fluctuations in (Y,Nd)Ba2Cu3O6+x

A State of High Tc Superconductivity There are strong indications that high-temperature superconductivity in the cuprates is formed amid competing orders, but only two have been observed unambiguously. The so-called stripe order has been observed in a Lanthanum-based cuprate family and consists of coexisting charge-and-spin modulations and occurs at a characteristic dopant concentration in which the critical temperature Tc has a dip. Now, Ghiringhelli et al. (p. 821, published online 12 July; see the Perspective by Tranquada) have used resonant inelastic x-ray scattering to uncover a related but apparently two-dimensional charge order in the much cleaner YBCO cuprate family. The charge fluctuations were not commensurate with the lattice and did not originate in the characteristic oxygen chains of YBCO. The order appeared only in a narrow interval of dopant concentrations and competed with superconductivity, which provides a natural explanation for a plateau in Tc observed in the same range. Scattering experiments uncover an order competing with superconductivity in a cuprate family. The concept that superconductivity competes with other orders in cuprate superconductors has become increasingly apparent, but obtaining direct evidence with bulk-sensitive probes is challenging. We have used resonant soft x-ray scattering to identify two-dimensional charge fluctuations with an incommensurate periodicity of ~3.2 lattice units in the copper-oxide planes of the superconductors (Y,Nd)Ba2Cu3O6+x, with hole concentrations of 0.09 to 0.13 per planar Cu ion. The intensity and correlation length of the fluctuation signal increase strongly upon cooling down to the superconducting transition temperature (Tc); further cooling below Tc abruptly reverses the divergence of the charge correlations. In combination with earlier observations of a large gap in the spin excitation spectrum, these data indicate an incipient charge density wave instability that competes with superconductivity.

Evidence of orbital reconstruction at interfaces in ultrathin La0.67Sr0.33MnO3 films.

Linear dichroism (LD) in x-ray absorption, diffraction, transport, and magnetization measurements on thin La(0.7)Sr(0.3)MnO(3) films grown on different substrates, allow identification of a peculiar interface effect, related just to the presence of the interface. We report the LD signature of preferential 3d-e(g)(3z(2)-r(2)) occupation at the interface, suppressing the double exchange mechanism. This surface orbital reconstruction is opposite to that favored by residual strain and is independent of dipolar fields, the chemical nature of the substrate and the presence of capping layers.

SAXES, a high resolution spectrometer for resonant x-ray emission in the 400-1600 eV energy range

We present a 5m long spectrometer for soft x rays to be used at a synchrotron radiation beamline for resonant x-ray emission spectroscopy and resonant inelastic x-ray scattering in the 400–1600eV energy range. It is based on a variable line spacing spherical grating (average groove density of 3200mm−1, R=58.55m) and a charge coupled device two dimensional detector. With an x-ray spot on the sample of 10μm, the targeted resolving power is higher than 10 000 at all energies below 1100eV and better than 7000 at 1500eV. The off-line tests made with Al and MgKα1,2 fluorescence emissions indicate that the spectrometer can actually work at 12 000 and 17 000 resolving power at the L3 edges of Cu (930eV) and of Ti (470eV), respectively. SAXES (superadvanced x-ray emission spectrometer) is mounted on a rotating platform allowing to vary the scattering angle from 25° to 130°. The spectrometer will be operational at the ADRESS (advanced resonant spectroscopies) beamline of the Swiss Light Source from 2007.

Charge order and its connection with Fermi-liquid charge transport in a pristine high- T c cuprate

Charge-density-wave (CDW) correlations within the quintessential CuO

Covalency in the uranyl ion: A polarized x-ray spectroscopic study

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Persistence of magnetic excitations in La2−xSrxCuO4 from the undoped insulator to the heavily overdoped non-superconducting metal

planes have been argued to either cause [1] or compete with [2] the superconductivity in the cuprates, and they might furthermore drive the Fermi-surface reconstruction in high magnetic fields implied by quantum oscillation (QO) experiments for YBa

Interaction of oxygen with silicon d‐metal interfaces: A photoemission investigation

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Looking 100 Å deep into spatially inhomogeneous dilute systems with hard x-ray photoemission

Cu

Collective Magnetic Excitations in the Spin Ladder Sr14Cu24O41 Measured Using High-Resolution Resonant Inelastic X-Ray Scattering

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Theoretical Demonstration of How the Dispersion of Magnetic Excitations in Cuprate Compounds can be Determined Using Resonant Inelastic X-Ray Scattering

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