排序方式: 共有37条查询结果,搜索用时 46 毫秒
21.
Glawion S Heidler J Haverkort MW Duda LC Schmitt T Strocov VN Monney C Zhou KJ Ruff A Sing M Claessen R 《Physical review letters》2011,107(10):107402
We combine high-resolution resonant inelastic x-ray scattering with cluster calculations utilizing a recently derived effective magnetic scattering operator to analyze the polarization, excitation energy, and momentum-dependent excitation spectrum of the low-dimensional quantum magnet TiOCl in the range expected for orbital and magnetic excitations (0-2.5?eV). Ti 3d orbital excitations yield complete information on the temperature-dependent crystal-field splitting. In the spin-Peierls phase we observe a dispersive two-spinon excitation and estimate the inter- and intradimer magnetic exchange coupling from a comparison to cluster calculations. 相似文献
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The sila-β-diketone, 2,2,6,6-tetramethyl-2-silaheptane-3,5-dione (tmshdH), was synthesized by the condensation of the anion of 2-trimethylsilyl-1,3-dithiane with 1-bromo-3,3-dimethylbutan-2-one, followed by unmasking of the latent carbonyl moiety with HgO/HgCl2. A monoclinic polymorph of the known copper(II) complex, Cu(tmshd)2, was crystallized and studied by X-ray diffraction methods and found to be disordered like the orthorhombic one. Attempts to synthesize the disilylated β-diketone, 2,2,6,6-tetramethyl-2,6-disilaheptane-3,5-dione and monosilylated 4,4-dimethyl-4-sila-3-oxo-pentanal using the dithiane method were not successful. However, the 1,3-dithianyl precursors, along with the impurity 2,2′-bis(trimethylsilyl)-2,2′-bi-1,3-dithiane, were studied crystallographically. Large stereoelectronic and steric effects on the solid-state bonding parameters were observed for these molecules. 相似文献
23.
F. Reinert P. Steiner R. Zimmermann R. Claessen S. Hüfner 《Zeitschrift für Physik B Condensed Matter》1995,99(2):229-234
The valence band of potassium permanganate (KMnO4) was investigated by means of resonant photoemission spectroscopy (ResPES) at the Mn2p, Mn3p and O1s edge. These data confirm the previous conclusions of a strong deviation from a purely ionic charge distribution in this compound. The ResPES data are in agreement with previous results about the character of the individual valence band states. A simple cluster model is used to explain qualitatively the different structures seen in the valence band spectra and their dependence on the photon energy. 相似文献
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Claessen R Sing M Schwingenschlögl U Blaha P Dressel M Jacobsen CS 《Physical review letters》2002,88(9):096402
The electronic structure of the quasi-one-dimensional organic conductor TTF-TCNQ is studied by angle-resolved photoelectron spectroscopy (ARPES). The experimental spectra reveal significant discrepancies to band theory. We demonstrate that the measured dispersions can be consistently mapped onto the one-dimensional Hubbard model at finite doping. This interpretation is further supported by a remarkable transfer of spectral weight as a function of temperature. The ARPES data thus show spectroscopic signatures of spin-charge separation on an energy scale of the conduction bandwidth. 相似文献
26.
Hole-accumulation layers on silicon (100) are studied using resonant inelastic light scattering techniques. The observed intersubband transitions are in good agreement with Hartree calculations of Bangert and with recent infrared absorption experiments. The width of the spectra can be explained qualitatively using the nonparabolic k| dispersion of the individual subbands. 相似文献
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L.M. Claessen J.C. Maan M. Altarelli P. Wyder L.L. Chang L. Esaki 《Superlattices and Microstructures》1986,2(6)
Using magneto-optical methods, we have measured the energy separation between the subbands in a semimettalic InAs---GaSb superlattice associated with the InAs conduction band (CB) and the GaSb valence band (VB) as a function of hydrostatic pressure up to 11kBar. The CB-VB energy overlap (Δ) at the InAs---GaSb interface is found to depend less on pressure than predicted on grounds of usual assumptions concerning band energy shifts induced by pressure.Also inter-subband coupling has been observed between the bands in different adjacent materials. This coupling is found to lead to anti-crossing in the subband dispersion relation. 相似文献
29.
Schäfer J Sing M Claessen R Rotenberg E Zhou XJ Thorne RE Kevan SD 《Physical review letters》2003,91(6):066401
Low-temperature electronic properties of the charge-density-wave system NbSe3 are reported from angle-resolved photoemission at 15 K. The effect of two instabilities q(1) and q(2) on the k-resolved spectral function is observed for the first time. With a pseudogap background, the gap spectra exhibit maxima at Delta*(1) approximately 110 meV and Delta*(2) approximately 45 meV. Imperfectly nested sections of the Fermi surface lack a Fermi-Dirac edge, and show the signature of a dispersion that is modified by self-energy effects. The energy scale is of the order of the effective gap 2 Delta*(2). The effect disappears above T2, suggesting a correlation with the charge-density-wave state. 相似文献
30.
Stekolnikov AA Bechstedt F Wisniewski M Schäfer J Claessen R 《Physical review letters》2008,100(19):196101
Combining total-energy calculations, electronic-structure studies, and scanning tunneling microscopy (STM), we demonstrate that the observed one-dimensional nanowires are composed of Pt-induced Ge structures instead of Pt chains. Pt-Ge bonds are favored versus Pt-Pt ones. The novel tetramer-dimer-chain model explains STM features and the differential conductivity. The conduction path is related to the chain of alternating Pt-Ge atoms. 相似文献