We performed a full mapping of the bulk electronic structure including the Fermi surface and Fermi-velocity distribution v(k) of tungsten. The 4D spectral function ρ(E; k) in the entire bulk Brillouin zone and 6 eV binding-energy (E) interval was acquired in ∼3 h thanks to a new multidimensional photoemission data-recording technique (combining full-field k-microscopy with time-of-flight parallel energy recording) and the high brilliance of the soft X-rays used. A direct comparison of bulk and surface spectral functions (taken at low photon energies) reveals a time-reversal-invariant surface state in a local bandgap in the (110)-projected bulk band structure. The surface state connects hole and electron pockets that would otherwise be separated by an indirect local bandgap. We confirmed its Dirac-like spin texture by spin-filtered momentum imaging. The measured 4D data array enables extraction of the 3D dispersion of all bands, all energy isosurfaces, electron velocities, hole or electron conductivity, effective mass and inner potential by simple algorithms without approximations. The high-Z bcc metals with large spin-orbit-induced bandgaps are discussed as candidates for topologically non-trivial surface states.

Typical Kondo insulators (KIs) can have a nontrivial Z_{2} topology because the energy gap opens at the Fermi energy (E_{F}) by a hybridization between odd- and even-parity bands. SmB_{6} deviates from such KI behavior, and it has been unclear how the insulating phase occurs. Here, we demonstrate that charge fluctuations are the origin of the topological insulating phase in SmB_{6}. Our angle-resolved photoemission spectroscopy results reveal that with decreasing temperature the bottom of the d-f hybridized band at the X[over ¯] point, which is predicted to have odd parity and is required for a topological phase, gradually shifts from below to above E_{F}. We conclude that SmB_{6} is a charge-fluctuating topological insulator.

Über die Acetochlor‐Verbindung des Lactaminsäure‐methylesters wurde nach Koenigs‐Knorr ein Methylketosid‐methylester von [α] D20: −6° erhalten, der von Neuraminidase quantitativ gespalten wird. Der aus Lactaminsäure mit H⊕ und Methanol dargestellte anomere Methylketosid‐methylester von [α]D20: −46° wird von dem Enzym nicht angegriffen. Bei den durch Verseifung der CO2CH3‐Gruppen erhaltenen anomeren Methoxycarbonsäuren besteht derselbe Unterschied.

The surface electronic structure of the narrow-gap seminconductor BiTeI exhibits a large Rashba-splitting which strongly depends on the surface termination. Here we report on a detailed investigation of the surface morphology and electronic properties of cleaved BiTeI single crystals by scanning tunneling microscopy, photoelectron spectroscopy (ARPES, XPS), electron diffraction (SPA-LEED) and density functional theory calculations. Our measurements confirm a previously reported coexistence of Te-and I-terminated surface areas

Photoemission-intensity distributions I RCP/LCP (E B , k) measured for right-and left-circularly polarized soft x-rays revealed a large circular dichroism in angular distribution (CDAD) in the 4D parameter space (E B binding energy, k momentum vector). Full-field k-imaging combined with timeof-flight energy recording at a high-brilliance soft x-ray beamline allowed mapping the CDAD in the bulk Brillouin zone of tungsten and the entire d-band complex within a few hours. CDADasymmetries are very high (up to 90%), persist throughout the whole photon-energy range (300-1300 eV) and show a pronounced dependence on momentum k and binding energy E B , visualized as movies or sequences of cuts through the 4D object. One-step photoemission calculations for the same photon energies show fair agreement with the measured results. In addition to the requirement of a 'handed' experimental geometry, known from previous experiments on adsorbates and surface states, we find an anti-symmetric behavior of the CDAD with respect to two bulk mirror planes. A new symmetry condition along the perpendicular momentum k z makes CDAD a valuable tool for an unambiguous identification of high-symmetry planes in direct transitions in the periodic zone scheme. Technically, the method provides a circular polarimeter for soft, tender and hard x-rays. being sensitive to their phase-shift differences. The differential photoemission cross section is proportional to the squared total dipole matrix element that contains interference terms between different final-state partial waves. Upon reversal of the photon helicity (in case of CDAD) or switching of the electric vector between orthogonal directions (for LDAD), interference terms with odd symmetry change their signs. This is the origin of the dichroism in the photoelectron angular distribution. This phenomenon exists in the pure electric dipole approximation and thus it differs from the 'natural' CD of chiral molecules, which is described by higher-order terms in the electron-photon operator [14].In the present work we employ the technique of time-of-flight (ToF) k-microscopy for a comprehensive study of the CDAD in the soft-x-ray spectral range. This new method captures simultaneously more than one full Brillouin zone (BZ) for binding energies in a range of several eV, yielding full information from the valence bands. In the vacuum ultraviolet (VUV) range, this instrument was previously used for the study of LDAD in photoemission from Mo(110) surface states and surface resonances [15]. These states are characterized by their 2D character and their location at the surface, wherefore they fulfill the criteria discussed for adsorbate systems [13]. Earlier work on graphite [16] and Pd [17] revealed that a CDAD also exists in photoemission from crystalline samples. However, the low photon energies used essentially probe the surface character of the bands. Hence, these results cannot be considered representative for true 3D bulk states. Moreover, no information on the dependence of the CDAD on the electro...