第80回フロンティア材料研究所講演会
80th MSL Lecture
Date/Time:

14:00 – 15:30, Monday, November 12thVenue:

1F Meeting Room, Building R3

Speaker:Prof. Shigemasa SUGA

Institute of Scientific & Industrial Research, Osaka University, Japan
Forschungszentrum Jülich, PGI-6, Germany

Frontier of Photoelectron Spectroscopy and Resonance Inelastic X-ray
Scattering in Solids
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 andaberration corrected tandem S-type double hemispherical deflection analyzers (DHDAs) has opened abreakthrough. 2D EB(kx,ky) can be simultaneously measured in a very wide k space with such highresolutions as ∆E<12 meV & ∆k < 0.005 Å-1. Nearly 104 (kx,ky) points can be measured over a widesurface/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 spinasymmetric 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 spindetector 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, photonin/photon-out experiment as RIXS is ideal. Here the micro-nano study requires the focusing of theexcitation synchrotron radiation. Still the surface radiation damage is not serious because RIXS is reallybulk sensitive. Great advantage of RIXS is the feasibility of measurements under any externalperturbations. 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 1step 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 setsof experiments.
References
1. S.Suga and C.Tusche, Photoelectron spectroscopy in a wide hν 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).

Contact: Yuichiro Matsushita(ext. 5343)