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BiS2-based layered superconductors are new superconductors, having been paid special attention due to the layered crystal structure and the characteristic electronic structure that can lead to exotic mechanism of superconductivity as well as cooperation of superconductivity and ordered phases. In this article, we report valence band dispersions and Fermi surface topology of LaO1-xFxBiS2 (x = 0.23, Tc < 2 K) studied by angle-resolved photoemission spectroscopy, and compared them with those of LaO1-xFxBiS2 (x = 0.46, Tc = 3.1 K). We discuss experimental x dependent electronic structures and its relation to Tc. We also point to anomalous spectroscopic features in LaO1-xFxBiS2 (x = 0.46) that can be explained by band structure calculations considering distorted lattice, suggesting role of dynamical or static lattice distortion to the physical properties.

Bulk electronic structure of novel layered superconductor Nd(O,F)BiS2 was studied by using soft x-ray angle-resolved photoelectron spectroscopy (ARPES). Electron-like Fermi surface centered at the X(R) point was observed, consistent with earlier ARPES reports on surface-sensitive VUV light source. Based on the comparison of the electronic structure between Nd(O,F)BiS2 and La(O,F)BiS2, we discuss possible important factors for the superconductivity in this series of material.

We have measured the temperature-dependent X-ray diffraction pattern of a single-crystalline EuO (100) thin film to investigate the change of the lattice constant due to the ferromagnetic phase transition. No structural transition was observed and the contracting rate of the lattice constant was dramatically increases below the ferromagnetic phase transition temperature. It indicates that the hybridization intensity between the Eu 4f state and the other O 2p and Eu 5d states increases in the ferromagnetic phase.