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We report on directly determining the complex permittivity tensor using a method combining a developed light source from a segmented cross undulator of synchrotron radiation and the magneto-optical Kerr effect. The empirical permittivity, which carries the electronic and magnetic information of a material, has element specificity and has perfect confirmation using the quantum-mechanical calculation for itinerant electrons systems. These results help in understanding the interaction of light and matter, and they provide an interesting approach to seek the best materials as optical elements, for example, in extended-ultraviolet lithographic technologies or in state-of-the-art laser technologies. [ABSTRACT FROM AUTHOR]

The Fe L-edge resonant magneto-optical Kerr effect of a buried Fe nanofilm was investigated by rotating-analyzer ellipsometry and the results were compared with those from three theoretical simulations. The reversal of the Kerr rotation angle θK between the L3 and L2 edges, observed in the experiment, was consistent with classical electromagnetic simulation using empirical optical constants. The spectral θK feature was reproduced by the first-principles calculation of the KKR-Green's function method on the itinerant electronic system. The demonstration indicates that spectra of the L-edge resonant MOKE can be understood in terms of both the macroscopic and microscopic pictures. [ABSTRACT FROM AUTHOR]

The transient single-particle spectral function of BaFe2As2, a parent compound of iron-based superconductors, has been studied by time- and angle-resolved photoemission spectroscopy with an extreme-ultraviolet laser generated by higher harmonics from Ar gas, which enables us to investigate the dynamics in the entire Brillouin zone. We observed electronic modifications from the spin density wave (SDW) ordered state within ~1 ps after the arrival of a 1.5 eV pump pulse. We observed optically excited electrons at the zone center above EF at 0.12 ps, and their rapid decay. After the fast decay of the optically excited electrons, a thermalized state appears and survives for a relatively long time. From a comparison with the density-functional theory band structure for the paramagnetic and SDW states, we interpret the experimental observations as the melting of the SDW. Exponential decay constants for the thermalized state to recover back to the SDW ground state are ~0.60 ps both around the zone center and the zone corner. [ABSTRACT FROM AUTHOR]

The topology of pure Bi is controversial because of its very small (~10 meV) band gap. Here we perform high-resolution angle-resolved photoelectron spectroscopy measurements systematically on 14-202 bilayer Bi films. Using high-quality films, we succeed in observing quantized bulk bands with energy separations down to ~10 meV. Detailed analyses on the phase shift of the confined wave functions precisely determine the surface and bulk electronic structures, which unambiguously show nontrivial topology. The present results not only prove the fundamental property of Bi but also introduce a capability of the quantum-confinement approach. [ABSTRACT FROM AUTHOR]