Interfacial-Redox-Induced Tuning of Superconductivity in YBaCuO.

Solid-state ionic approaches for modifying ion distributions in getter/oxide heterostructures offer exciting potentials to control material properties. Here, we report a simple, scalable approach allowing for manipulation of the superconducting transition in optimally doped YBaCuO (YBCO) films via a chemically driven ionic migration mechanism. Using a thin Gd capping layer of up to 20 nm deposited onto 100 nm thick epitaxial YBCO films, oxygen is found to leach from deep within the YBCO.

Phonon dispersion of Mo-stabilized -U measured using inelastic x-ray scattering.

We have measured the room-temperature phonon spectrum of Mo-stabilized -U. The dispersion curves show unusual softening near the point, = [12, 12, 12], which may derive from the metastability of the -U phase or from strong electron-phonon coupling. Near the zone center, the dispersion curves agree well with theory, though significant differences are observed away from the zone center.

Pressure dependence of Ce valence in CeRhIn.

We have studied the Ce valence as a function of pressure in CeRhIn at 300 K and at 22 K using x-ray absorption spectroscopy in partial fluorescent yield mode. At room temperature, we found no detectable change in Ce valence greater than 0.01 up to a pressure of 5.

Note: Manganin foil sensor for small uniaxial stress.

We describe a simple manganin foil resistance manometer for uniaxial stress measurements. The manometer functions at low pressures and over a range of temperatures. In this design, no temperature seasoning is necessary although the manometer must be prestressed to the upper end of the desired pressure range.

Anisotropic dependence of superconductivity on uniaxial pressure in CeIrIn5.

We measure the effect of uniaxial pressure on the superconducting transition temperature T_{c} in CeIrIn5. We find a linear change in T_{c} with both a-axis and c-axis pressure, with slopes of 56 and -66 mK/kbar, respectively. By comparing results from doping studies and different types of pressure measurements, we separate the influences of hybridization and dimensionality on T_{c}.