In this study, we systematically investigate three-dimensional (3D) momentum ( k)-resolved electronic structures of Ruddlesden-Popper-type iridium oxides Sr n+1 Ir n O 3n+1 using soft-x-ray (SX) angle-resolved photoemission spectroscopy (ARPES). Our results provide direct evidence of an insulator-to-metal transition that occurs upon increasing the dimensionality of the IrO 2 -plane structure. This transition occurs when the spin-orbit-coupled j eff = 1/2 band changes its behavior in the dispersion relation and moves across the Fermi energy. In addition, an emerging band along the (0,0,0)-R(π,π,π) direction is found to play a crucial role in the metallic characteristics of SrIrO 3 . By scanning the photon energy over 350 eV, we reveal the 3D Fermi surface in SrIrO 3 and k z -dependent oscillations of photoelectron intensity in Sr 3 Ir 2 O 7 . In contrast to previously reported results obtained using low-energy photons, folded bands derived from lattice distortions and/or magnetic ordering make significantly weak (but finite) contributions to the k-resolved photoemission spectrum. At the first glance, this leads to the ambiguous result that the observed k-space topology is consistent with the unfolded Brillouin zone (BZ) picture derived from a nonrealistic simple square or cubic Ir lattice. Through careful analysis, we determine that a superposition of the folded and unfolded band structures has been observed in the ARPES spectra obtained using photons in both ultraviolet and SX regions. To corroborate the physics deduced using low-energy ARPES studies, we propose to utilize SX-ARPES as a powerful complementary technique, as this method surveys more than one whole BZ and provides a panoramic view of electronic structures.

No abstract

The hyperfine-enhanced nuclear moment in TmP04 was studied by SQUID NMR. A resonance frequency yx/2~r = 274 MHz per tesla was obtained, leading to an enhancement factor of 77.9. The temperature dependence of the spin-lattice relaxation time T1 of 169Tm nuclear spin in TraP04 was measured at liquid helium temperatures. The temperature dependence of T1 can be understood in terms of nuclear Orbach and direct processes.

No abstract

This paper compares the measured characteristics of a three-dimensional Nb thin-film point-contact junction with those predicted by the Stewart-McCumber model. The erratic microwave-induced I-V characteristic we observed at low microwave power levels was also evident in a digital simulation –based on the Stewart-McCumber model–of the time dependence of the junction voltage and the phase space trajectory. Subharmonic steps V=(n/m)(h f/2e) were observed when a 70 GHz signal was applied, but the usual condition ωC R n≃1 for substeps was not fulfilled. Substeps were also observed in the digital simulation even when the current-phase relationship was purely sinusoidal.