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第80回フロンティア材料研究所講演会 (Prof. Shigemasa SUGA)

開催日時 2018年11月12日 14:00 -15:30
開催場所 R3棟1階会議室
主催フロンティア材料研究所
連絡先松下 雄一郎 特任講師 (内線:5343)

プログラム等

第80回フロンティア材料研究所講演会

講師: Prof. Shigemasa SUGA
    (Institute of Scientific & Industrial Research, Osaka University, Japan
     Forschungszentrum Jülich, PGI-6, Germany)

演題:
 Frontier of Photoelectron Spectroscopy and Resonance Inelastic X-ray Scattering in Solids

講演概要:
 High resolution & multi-dimensional spin- & angle-resolved photoelectron spectroscopy (ARPES) in micro-nano regions is required in recent years for both fundamental researches and device development. However, extremely low spin detection efficiency has so far hindered its progress. Development of the momentum microscope (M.M.) composed of a PEEM type input lens and aberration corrected tandem S-type double hemispherical deflection analyzers (DHDAs) has opened a breakthrough. 2D EB(kx,ky) can be simultaneously measured in a very wide k space with such high resolutions as ΔE<12 meV & Δk < 0.005 Å-1. Nearly 104 (kx,ky) points can be measured over a wide surface/bulk Brillouin zones (BZs) at the same time for a certain EK(or EB),which is then scanned. Long life time 2D imaging spin filter such as Au/Ir(001) can be installed behind this M.M. Then spin-asymmetric 2D EB(kx,ky) images can be recorded at two electron incidence energies (10.25 & 11.5 eV) with about ±60% spin sensitivity. From these two spectra, spin resolved spectrum in the wide k space is easily derived in the form of Ps(EB(kx,ky)). Even 3D Ps(EB(kx,ky,kz) is obtained by changing the hν. Since the PEEM can collect electrons emitted into wide solid angles, 2D multi-channel figure of merit (FoM) of this spin detection is ∼millions or ∼billions times higher than the single channel Fe-O VLEED spin detector or Mott and spin-LEED spin detector. Examples of surface Rashba states as well as Dirac cone states of topological insulators are presented, showing the necessity of experiments by M.M. Although detailed knowledge of the electronic structures in non-conductive materials is desired nowadays, (AR)PES cannot be applied because of the charging up effects. In such a case, photon-in/photon-out experiment as RIXS is ideal. Here the micro-nano study requires the focusing of the excitation synchrotron radiation. Still the surface radiation damage is not serious because RIXS is really bulk sensitive. Great advantage of RIXS is the feasibility of measurements under any external perturbations. Standard RIXS of V and Cr oxides as well as RIXS of half metal Heusler alloy Mn2VAl under external magnetic field are discussed. In both cases, advanced theoretical calculations based on the 1st principles band calculations and 1 step model calculations of the photoelectron spectra fully taking into account the experimental configurations and/or the intermediate states are required. Intense collaborations between experimentalists and theoreticians are now demanded for reliable understanding of the full data sets of experiments.

 References
1. S.Suga and C.Tusche, Photoelectron spectroscopy in a wide h region from 6 eV to 8 keV with full momentum and spin resolution, J.Electron Spectrosc. Rel. Phenom. 200, 119-142 (2015)
2. S.Suga and A.Sekiyama, Photoelectron Spectroscopy: Bulk and Surface Electronic Structures, Springer Series in Optical Sciences 176, 1-378 (2014).
3. K.Nagai, H. Fujiwara, S. Suga, R. Y. Umetsu et al., Phys.Rev.B97, 035143 (2018).

 

 

 

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