The Largest Blueshifts of [O III] emission line in Two Narrow-Line Quasars

We have obtained optical intermediate resolution spectra (R = 3000) of the narrow-line quasars DMS 0059-0055 and PG 1543+489. The [O III] emission line in DMS 0059-0055 is blueshifted by 880 km/s relative to Hbeta. We also confirm that the [O III] emission line in PG 1543+489 has a relative blueshift of 1150 km/s. These two narrow-line quasars show the largest [O III] blueshifts known to date among type 1 active galactic nuclei (AGNs). The [O III] emission lines in both objects are broad (1000 - 2000 km/s) and those in DMS 0059-0055 show strong blue asymmetry. We interpret the large blueshift and the profile of the [O III] lines as the result of an outflow interacting with circumnuclear gas. Among type 1 AGNs with large blueshifted [O III], there is no correlation between the Eddington ratios and the amount of [O III] blueshifts. Combining our new data with published results, we confirm that the Eddington ratios of the such AGNs are the highest among AGNs with the same black hole masses. These facts suggest that the Eddington ratio is a necessary condition or the [O III] blueshifts weakly depend on the Eddington ratio. Our new sample suggests that there are possible necessary conditions to produce an outflow besides a high Eddington ratio: large black hole mass (> 10^7 M_solar) or high mass accretion rate (> 2 M_solar/yr) or large luminosity (lambda L_{lambda} (5100A) > 10^44.6 erg/s).Comment: Accepted for publication in The Astrophysical Journa

Universal scaling for the spin-electricity conversion on surface states of topological insulators

We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin pumping technique. The sample structure is Ni-Fe|Cu|TI trilayers, in which magnetic proximity effects on the TI surfaces are negligibly small owing to the inserted Cu layer. Voltage signals produced by the spin-electricity conversion are clearly observed, and enhanced with decreasing temperature in line with the dominated surface transport at lower temperatures. The efficiency of the spin-electricity conversion is greater for TI samples with higher resistivity of bulk states and longer mean free path of surface states, consistent with the surface spin-electricity conversion

Chemical potential jump between hole- and electron-doped sides of ambipolar high-Tc cuprate

In order to study an intrinsic chemical potential jump between the hole- and electron-doped high-Tc superconductors, we have performed core-level X-ray photoemission spectroscopy (XPS) measurements of Y0.38La0.62Ba1.74La0.26Cu3Oy (YLBLCO), into which one can dope both holes and electrons with maintaining the same crystal structure. Unlike the case between the hole-doped system La_2-xSrxCuO4 and the electron-doped system Nd_2-xCexCuO4, we have estimated the true chemical potential jump between the hole- and electron-doped YLBLCO to be ~0.8 eV, which is much smaller than the optical gaps of 1.4-1.7 eV reported for the parent insulating compounds. We attribute the reduced jump to the indirect nature of the charge-excitation gap as well as to the polaronic nature of the doped carriers.Comment: 4 pages, 3 figure

Manipulation of Topological States and Bulk Band Gap Using Natural Heterostructures of a Topological Insulator

We have performed angle-resolved photoemission spectroscopy on (PbSe)5(Bi2Se3)3m, which forms a natural multilayer heterostructure consisting of a topological insulator (TI) and an ordinary insulator. For m = 2, we observed a gapped Dirac-cone state within the bulk-band gap, suggesting that the topological interface states are effectively encapsulated by block layers; furthermore, it was found that the quantum confinement effect of the band dispersions of Bi2Se3 layers enhances the effective bulk-band gap to 0.5 eV, the largest ever observed in TIs. In addition, we found that the system is no longer in the topological phase at m = 1, pointing to a topological phase transition between m = 1 and 2. These results demonstrate that utilization of naturally-occurring heterostructures is a new promising strategy for realizing exotic quantum phenomena and device applications of TIs.Comment: 5 pages, 5 figure

Direct Measurement of the Out-of-Plane Spin Texture in the Dirac Cone Surface State of a Topological Insulator

We have performed spin- and angle-resolved photoemission spectroscopy of Bi2Te3 and present the first direct evidence for the existence of the out-of-plane spin component on the surface state of a topological insulator. We found that the magnitude of the out-of-plane spin polarization on a hexagonally deformed Fermi surface (FS) of Bi2Te3 reaches maximally 25% of the in-plane counterpart while such a sizable out-of-plane spin component does not exist in the more circular FS of TlBiSe2, indicating that the hexagonal deformation of the FS is responsible for the deviation from the ideal helical spin texture. The observed out-of-plane polarization is much smaller than that expected from existing theory, suggesting that an additional ingredient is necessary for correctly understanding the surface spin polarization in Bi2Te3.Comment: 4 pages, 3 figure