排序方式: 共有29条查询结果,搜索用时 31 毫秒
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Denlinger JD Clack JA Allen JW Gweon GH Poirier DM Olson CG Sarrao JL Bianchi AD Fisk Z 《Physical review letters》2002,89(15):157601
Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for many-body quasiparticle band calculations. 相似文献
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β‐ or α,β‐Substituted vinylpyridines react with 3,3‐dimethylbut‐1‐ene in the presence of Wilkinson catalyst [RhCl(PPh3)3] to give the corresponding alkylated products along with unusually isomerized products. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:346–350, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10045 相似文献
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Kinetic studies on the oxidation of carbon monoxide over pure,reduced, and doped indium sesquioxides
Kinetic studies on the oxidation of carbon monoxide have been carried out between 413 and 473 K at different partial pressures of carbon monoxide and oxygen by means of the static method using vacuum-activated, hydrogen-reduced, and NiO-doped In2O3 semiconductors as catalysts. A strong carbon dioxide inhibiting effect is observed. The experimental data satisfactorily fit an equation derived by assuming the controlling step to be the adsorption of gaseous oxygen on the surface of catalyst. CO and CO2 adsorb on the lattice oxygens (O), while O2 adsorbs on the oxygen vacancies (V) formed by vacuum-activation, H2-reduction, and NiO-doping of In2O3. When CO2 formed during the reaction is removed by means of liquid nitrogen trap, the oxidation is found to be first-order with respect to CO and to be half-order with respect to O2. The concentration of oxygen vacancy in the solid catalyst is shown to be the controlling factor for the oxidation of carbon monoxide. A possible reaction mechanism can be explained by the n-type character of In2O3 and proposed from the experimentally obtained kinetic data and conductivities. 相似文献
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Filling of the mott-hubbard gap in the high temperature photoemission spectrum of (V0.972Cr0.028)2O3
Mo SK Kim HD Allen JW Gweon GH Denlinger JD Park JH Sekiyama A Yamasaki A Suga S Metcalf P Held K 《Physical review letters》2004,93(7):076404
Photoemission spectra of the paramagnetic insulating phase of (V0.972Cr0.028)2O3, taken in ultrahigh vacuum up to the unusually high temperature (T) of 800 K, reveal a property unique to the Mott-Hubbard (MH) insulator that has not been observed previously. With increasing T the MH gap is filled by spectral weight transfer, in qualitative agreement with high-T theoretical calculations combining dynamical mean field theory and band theory in the local density approximation. 相似文献
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Garcia DR Gweon GH Zhou SY Graf J Jozwiak CM Jung MH Kwon YS Lanzara A 《Physical review letters》2007,98(16):166403
We present the first direct study of charge density wave (CDW) formation in quasi-2D single layer LaTe2 using high-resolution angle resolved photoemission spectroscopy and low energy electron diffraction. CDW formation is driven by Fermi surface (FS) nesting, however, characterized by a surprisingly smaller gap ( approximately 50 meV) than seen in the double layer RTe2 compounds, extending over the entire FS. This establishes LaTe2 as the first reported semiconducting 2D CDW system where the CDW phase is FS nesting driven. In addition, the layer dependence of this phase in the tellurides and the possible transition from a stripe to a checkerboard phase is discussed. 相似文献
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Graf J Gweon GH McElroy K Zhou SY Jozwiak C Rotenberg E Bill A Sasagawa T Eisaki H Uchida S Takagi H Lee DH Lanzara A 《Physical review letters》2007,98(6):067004
A universal high energy anomaly in the single particle spectral function is reported in three different families of high temperature superconductors by using angle-resolved photoemission spectroscopy. As we follow the dispersing peak of the spectral function from the Fermi energy to the valence band complex, we find dispersion anomalies marked by two distinctive high energy scales, E1 approximately 0.38 eV and E2 approximately 0.8 eV. E1 marks the energy above which the dispersion splits into two branches. One is a continuation of the near parabolic dispersion, albeit with reduced spectral weight, and reaches the bottom of the band at the Gamma point at approximately 0.5 eV. The other is given by a peak in the momentum space, nearly independent of energy between E1 and E2. Above E2, a bandlike dispersion reemerges. We conjecture that these two energies mark the disintegration of the low-energy quasiparticles into a spinon and holon branch in the high Tc cuprates. 相似文献
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The normal-state single particle spectral function of the high temperature superconducting cuprates, measured by the angle-resolved photoelectron spectroscopy (ARPES), has been considered both anomalous and crucial to understand. Here, we report an unprecedented success of the new extremely correlated Fermi liquid theory by one of us [B. S. Shastry, Phys. Rev. Lett. 107, 056403 (2011)] to describe both laser and conventional synchrotron ARPES data (nodal cut at optimal doping) on Bi(2)Sr(2)CaCu(2)O(8+δ) and synchrotron data on La(1.85)Sr(0.15)CuO(4). It fits all data sets with the same physical parameter values, satisfies the particle sum rule and successfully addresses two widely discussed kink anomalies in the dispersion. 相似文献