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Monolayer VSe2, featuring both charge density wave and magnetism phenomena, represents a unique van der Waals magnet in the family of metallic 2D transition-metal dichalcogenides (2D-TMDs). Herein, by means of in situ microscopy and spectroscopic techniques, including scanning tunneling microscopy/spectroscopy, synchrotron X-ray and angle-resolved photoemission, and X-ray absorption, direct spectroscopic signatures are established, that identify the metallic 1T-phase and vanadium 3d1 electronic configuration in monolayer VSe2 grown on graphite by molecular-beam epitaxy. Element-specific X-ray magnetic circular dichroism, complemented with magnetic susceptibility measurements, further reveals monolayer VSe2 as a frustrated magnet, with its spins exhibiting subtle correlations, albeit in the absence of a long-range magnetic order down to 2 K and up to a 7 T magnetic field. This observation is attributed to the relative stability of the ferromagnetic and antiferromagnetic ground states, arising from its atomic-scale structural features, such as rotational disorders and edges. The results of this study extend the current understanding of metallic 2D-TMDs in the search for exotic low-dimensional quantum phenomena, and stimulate further theoretical and experimental studies on van der Waals monolayer magnets. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The intermolecular band dispersion related to the highest occupied molecular orbital of epitaxial anthracene multilayer films on single-crystalline Bi(0001) has been measured using angle-resolved ultraviolet photoelectron spectroscopy. By comparing the dispersion to that of anthracene multilayers on Cu(110) [F. Bussolotti, Y. Yamada-Takamura, and R. Friedlein, Phys. Rev. B 80, 153402 (2009)10.1103/PhysRevB.80.153402], it is shown how the transfer integrals and the difference in on-site energies depend on lattice parameters and how this, in turn, affects the band curvature along high-symmetry directions., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/10738

A single layer of bismuth deposited on the Cu(100) surface forms long range ordered structural phases at various Bi density. A highly ordered c (2×2) reconstruction is accomplished at 0.5 ML, further Bi deposition induces a c (92×2) R45° structure and a subsequent p (10×10) phase related to the formation of regular dislocations arrays. The transition from a c (2×2) superstructure to the c (92×2) R45° phase is accompanied by a sudden decrease in the work function. Photoemission measurements reveal that the Bi induced states close to the Fermi level, associated to the c (2×2) phase, are strongly quenched when the arrays of dislocations are formed, while at higher binding energies, they undergo an energy shift probably due to a confinement effect. The low-energy single particle excitations and the electron dispersion of the Bi induced states of the c (2×2) phase are compared to the electronic states deduced by theoretical band structure obtained by ab initio calculation performed within the embedding method applied to a realistic semi-infinite system. © 2010 American Institute of Physics.

We report on the crystal and electronic structures of single-crystalline anthracene multilayer films grown onto Cu(110) surfaces at 140 K. Electron diffraction patterns and angle-resolved ultraviolet photoelectron spectra are consistent with a thin film phase characterized by a “standing-up” molecular orientation and a squarelike unit cell within the plane of herringbone-stacked molecular layers. A single orientation of the film is achieved in an epitaxial relation with the lattice of the substrate surface. A clear dispersion of intermolecular bands relates anisotropic charge-carrier transport to particular crystallographic directions., identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/9522