Theoretical calculations for solid oxygen under high pressure

The crystal structure of solid oxygen at low temperatures and at pressures up to 7 GPa is studied by theoretical calculations. In the calculations, the adiabatic potential of the crystal is approximated by a superposition of pair-potentials between oxygen molecules calculated by an ab-initio method. The monoclinic alpha structure is stable up to 6 GPa and calculated lattice parameters agree well with experiments. The origin of a distortion and that of an anisotropic lattice compressibility of the basal plane of alpha-O2 are clearly demonstrated. In the pressure range from 6 to 7 GPa, two kinds of structures are proposed by X-ray diffraction experiments: the alpha and orthorhombic delta structures. It is found that the energy difference between these structures becomes very small in this pressure range. The relation between this trend and the incompatible results of X-ray diffraction experiments is discussed.Comment: 12 pages, 6 figure

Phase Transition in the 3-Kelvin Phase of Eutectic Sr₂RuO₄–Ru

The inhomogeneous 3-Kelvin (3K) phase of the eutectic Sr₂RuO₄ with Ru inclusions nucleates superconductivity at the interface between Ru and Sr₂RuO₄. The structure of the interface state and its physical properties are examined here. Two superconducting phases are identified between the transitions to the bulk phase at 1.5 K and to the 3K phase. The nucleation of the 3K phase results in a state conserving time reversal symmetry, which generates an intrinsically frustrated superconducting network in samples with many Ru inclusions. At a lower temperature (>1.5 K), a discontinuous (first order) transition to an interface state breaking time reversal symmetry is found leading to an unfrustrated network phase. It is shown that this phase transition located at a temperature between 1.5 and 3 K would yield the anomalous property showing that the critical current in such a network depends on the sign of the current, reproducing recent experimental observations

Analysis of Rashba Effect on Au(111) Model Surface

To understand the Rashba effect, the spin?orbit interaction (SOI) term in the Hamiltonian that has the dominant effect needs to be identified. Discrete variational-LDA (DV-LDA) calculations, i.e., LCAO-based DFT calculations, were performed to analyze the Rashba effect on a Au(111) surface. Results show that for the Rashba effect, the even-parity SOI is dominant and justifies the treatment of the SOI as the conventional l ・ s