S. Imada

Mutual Experimental and Theoretical Validation of Bulk Photoemission Spectra of Sr1 xCaxVO3

We report high-resolution high-energy photoemission spectra together with parameter-free LDA + DMFT (local density approximation + dynamical mean-field theory) results for Sr1-xCaxVO3, a prototype 3d(1) system. In contrast to earlier investigations the bulk spectra are found to be insensitive to x. The good agreement between experiment and theory confirms the bulk sensitivity of the high-energy photoemission spectra.

Strong Circular Dichroism in Photoelectron Diffraction from Nonchiral, Nonmagnetic Material–Direct Observation of Rotational Motion of Electrons

Strong circular dichroism is found in 2-dimensional angular distribution patterns of the Si 2p photoelectrons from the Si(001) surface, which has no chirality and magnetism. The forward focusing peaks in the pattern rotate clockwise or counterclockwise when the helicity of the incident circularly polarized light is reversed. These rotations of the pattern are explained by rotational motion of photoelectrons around the nuclei. This is the first direct observation of the rotational motion of the electrons and clarifies the correspondence between the classical and the quantum mechanical ideas of angular momentum.

Bulk 4f Electronic States of Ce-Based Heavy Fermion System Probed by High-Resolution Resonance Photoemission

“Bulk-sensitive” Ce 3 d -4 f resonance photoemission (RPES) with an unprecedentedly high resolution has revealed a clear difference of bulk Ce 4 f spectral weights of heavy fermion system CeRu 2 Si 2 and CeRu 2 Ge 2 in the region of the tail of the Kondo peak and its spin-orbit partner. The significant spectral difference in both materials is in strong contrast to the mutually similar “surface-sensitive” 4 d -4 f RPES. The obtained bulk-sensitive spectra are well reproduced by a single impurity model. Consideration of the crystalline electric field splitting is important for estimating a realistic Kondo temperature from the bulk 4 f spectra.

Magnetic Circular Dichroism in Core X-Ray Absorption Spectra of Rare-Earths

We present a calculation of magnetic circular dichroism in 3 d and 4 d core X-ray absorption spectra of rare earth systems assuming that a trivalent rare earth ion is placed in an infinitesimal uniform magnetic field. The calculation covers all rare earth elements between Ce and Tm. Features of the dichroism are explained by elementary considerations of transition matrix of a polarized light, spin-orbit coupling of a core hole, and exchange interaction between a core hole and a 4 f electron.

Twin helical undulator beamline for soft X-ray spectroscopy at SPring-8

A very high resolution soft X-ray beamline, BL25SU, has been designed and is under construction at SPring-8. Completely right or left circularly polarized light is supplied on a common axis of a newly designed twin helical undulator. A helicity modulation up to 10 Hz can be performed using five kicker magnets. The fundamental radiation covers the region 0.5-3 keV. Higher-order radiation is rather weak on the axis. A monochromator with varied-line-spacing plane gratings is installed to cover the region below 1.5 keV. A very high resolution beyond 10(4) is expected for the whole energy region.

The prominent 5d-orbital contribution to the conduction electrons in gold

We have examined the valence-band electronic structures of gold and silver in the same column in the periodic table with nominally filled d orbitals by means of a recently developed polarization-dependent hard x-ray photoemission. Contrary to a common expectation, it is found that the 5d-orbital electrons contribute prominently to the conduction electrons in gold while the conduction electrons in silver are to some extent free-electron-like with negligible 4d contribution, which could be related to a well-known fact that gold is more stable than silver in air. The 4d electron correlation effects are found to be essential for the conduction electron character in silver.

Kondo Lattice Effects of YbAl3 Suggested by Temperature Dependence of High-Accuracy High-Energy Photoelectron Spectroscopy

By use of high-resolution soft X-rays, intrinsic temperature dependences of bulk Yb 4f photoelectron spectra were obtained for fractured surfaces of high-purity YbAl 3 single crystals. The spectra ...

Structure factor in photoemission from valence band

Abstract Two-dimensional angular distribution of photoelectrons from valence band was analyzed using a tight-binding initial state. In simple cases, the angular distribution can be understood as a product of “ one-dimensional density of states (ODDOS)”, “ photoemission structure factor ”, and “ angular distribution from atomic orbital ”. This newly introduced “ photoemission structure factor ” is an intensity distribution in a reciprocal space similar to the X-ray or electron diffraction structure factor replacing scattering factor by the coefficient for each atomic orbital in the LCAO wavefunction. The remarkable symmetry-broken patterns observed from π band of single-crystalline graphite was clearly explained. The two-fold symmetry was obvious as the result of the “angular distribution from the pz atomic orbital” for the s- and linearly-polarized synchrotron radiation. The difference of the intensity in different BZs was clearly explained by the photoemission structure factor . Hence, the two-dimensional measurement can give us information not only (1)about the ODDOS, but also (2)about the symmetry of the initial state, and even more (3)about the coefficients in the initial state wavefunction.

Technique for bulk Fermiology by photoemission applied to layered ruthenates

We report the Fermi surfaces of the superconductor

Perpendicular magnetization of L10-ordered FePt films in the thinnest limit

{\mathrm{Sr}}_{2}{\mathrm{RuO}}_{4}