Nearly linear orbital molecules on a pyrochlore lattice.

The interplay of spin-orbit coupling with other relevant parameters gives rise to the rich phase competition in complex ruthenates featuring octahedrally coordinated Ru. While locally, spin-orbit coupling stabilizes a nonmagnetic = 0 state, intersite interactions resolve one of two distinct phases at low temperatures: an excitonic magnet stabilized by the magnetic exchange of upper-lying = 1 states or Ru molecular orbital dimers driven by direct orbital overlap. Pyrochlore ruthenates RuO ( = rare earth, Y) are candidate excitonic magnets with geometrical frustration.

Optical conductivity and superconductivity in highly overdoped La Ca CuO thin films.

We have used atomic layer-by-layer oxide molecular beam epitaxy to grow epitaxial thin films of [Formula: see text] with x up to 0.5, greatly exceeding the solubility limit of Ca in bulk systems ([Formula: see text]). A comparison of the optical conductivity measured by spectroscopic ellipsometry to prior predictions from dynamical mean-field theory demonstrates that the hole concentration p is approximately equal to x.

Revisiting Bond Breaking and Making in EuCo P : Where are the Electrons?

X-ray absorption spectroscopy (XAS) was used to elucidate changes in the electronic structure caused by the pressure-induced structural collapse in EuCo P . The spectral changes observed at the L -edge of Eu and K-edges of Co and P suggest electron density redistribution, which contradicts the formal charges calculated from the commonly used Zintl-Klemm concept. Quantum-chemical calculations show that, despite the increase in the oxidation state of Eu and the formation of a weak P-P bond in the high-pressure phase, the electron transfer from the Eu 4f orbitals to the hybridized 5d and 6s states causes strengthening of the Eu-P and P-P bonds.