Work function of bulk-insulating topological insulator Bi2-xSbxTe3-ySey

Recent discovery of bulk insulating topological insulator (TI) Bi2-xSbxTe3-ySey paved a pathway toward practical device application of TIs. For realizing TI-based devices, it is necessary to contact TIs with a metal. Since the band-bending at the interface dominates the character of devices, knowledge of TIs' work function is of essential importance. We have determined the compositional dependence of work function in Bi2-xSbxTe3-ySey by high-resolution photoemission spectroscopy. The obtained work-function values (4.95-5.20 eV) show a systematic variation with the composition, well tracking the energy shift of the surface chemical potential seen by angle-resolved photoemission spectroscopy. The present result serves as a useful guide for developing TI-based electronic devices.Comment: 4pages, 2 figure

Direct Evidence for the Dirac-Cone Topological Surface States in Ternary Chalcogenide TlBiSe2

We have performed high-resolution angle-resolved photoemission spectroscopy on TlBiSe2, which is a member of the ternary chalcogenides theoretically proposed as candidates for a new class of three-dimensional topological insulators. By measuring the energy band dispersions over the entire surface Brillouin zone, we found a direct evidence for a non-trivial surface metallic state showing a X-shaped energy dispersion within the bulk band gap. The present result unambiguously establishes that TlBiSe2 is a strong topological insulator with a single Dirac cone at the Brillouin-zone center. The observed bulk band gap of 0.4 eV is the largest among known topological insulators, making TlBiSe2 the most promising material for studying room-temperature topological phenomena.Comment: 4 pages, 4 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

Tomonotsuto (stone pagoda of tomonotsu) in Fukuyama city, Hiroshima <Data>

著者らは,鞆の浦の社寺建築および社寺境内の石造文化として特に重要と思われる鞆の津塔について調査を行う機会を得た。1 基ごとに実測図を作成し,さらに造立年代や構造形式などについて調査を行った。その結果,鞆の津塔は,五輪塔と宝篋印塔の部材を混在させた石塔と考えられた. また基礎正面に束で2 分割した格狭間,両側面に通常の格狭間を彫ること,さらに隅飾が同時代の宝篋印塔と比べて外側への傾斜が極めて少なく伝統的であることなどが特色として挙げられた。またおおよその造立年代が17 世紀頃と推測され,約100 年の間に集中的に造立されたという可能性が指摘できた。さらに規模が大きく,そのような石塔の施主が商人であることなどが注目され,裕福な商人の経済力を背景に造立されたものと考えられ,鞆の浦の港町としての繁栄を物語る歴史資料として重要である

Place of pitavastatin in the statin armamentarium: promising evidence for a role in diabetes mellitus

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, known as statins, have revolutionized the treatment of hypercholesterolemia and coronary artery disease prevention. However, there are considerable issues regarding statin safety and further development of residual risk control, particularly for diabetic and metabolic syndrome patients. Pitavastatin is a potent statin with low-density lipoprotein (LDL) cholesterol-lowering effects comparable to those of atorvastatin or rosuvastatin. Pitavastatin has a high-density lipoprotein (HDL) cholesterol raising effect, may improve insulin resistance, and has little influence on glucose metabolism. Considering these factors along with its unique pharmacokinetic properties, which suggest minimal drug–drug interaction, pitavastatin could provide an alternative treatment choice, especially in patients with glucose intolerance or diabetes mellitus. Many clinical trials are now underway to test the clinical efficacy of pitavastatin in various settings and are expected to provide further information

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