第15回　物理工学科教室談話会(講師：Prof. Shigemasa SUGA)

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概要：
Micro-nano electronics and spintronics devices are demanded in the frontier of ubiquitous society. Electron energy (EB) and spin (Ps) of materials down to 1) sub-mm, 2) tens nm or even 3) atomic scales are required, clarifying Ps(EB(kx,ky,kz) (x,y,z)). In addition, not only 4) conductors but also 5) insulators must be studied.
Standard angle resolved photoelectron spectroscopy (ARPES) is not enough for such purposes. It can’t be applied to 5) insulators and spatial regions 1),2),3). The extremely low efficient spin detection hinders the reliability of the experiment.
Difficulties 1),2) are now overcome by using spin-resolved two dimentional (2D) momentum microscope (abbreviated “SP-2D-MM”) with a million to sub-billion times higher spin ARPES detection efficiency. A photoelectron emission microscope (PEEM) is used as an entrance objective lens with the extraction voltage of 10-20kV. Whole emitted electrons into the 2p steradian can be guided then into the next electron energy analyzer composed of S-arranged aberration suppressed double hemispherical deflection analyzers, realizing high EB as well as k resolutions. Then either (x,y) or (kx,ky) image can be detected by a 2D detector with ~104 channels. When a Au/Ir(001) spin-filter is inserted at 45° before the 2D detector and the electrons are scattered at 10.25 and 11.5 eV with oppsosite spin sensitivity, 2D Ps(x,y) or 2D Ps(kx,ky) is simultaneously detected. Then spin polarization in many Brillouin zones(BZs) and wide EB regions of selected 1),2) regions can be easily measured, promoting various device development. If spin polarized STM is connected to this system, very practical analyses down to 3) may become feasible.
For the study of insulators, ARPES is not powerful. Then photon-in/photon-out resonance inelastic soft X ray scattering (SX-RIXS) is feasible which can be performed under external perturbations such as H, E, uniaxial strain, and so on providing useful information if the light beam can be focussed down to 1).
A door to new era of spectroscopy of micro-nano solids is opened. Close cooperation among scientists, materials engineers and theoreticians on the 1st principles band calculations in full BZs is highly demanded on the international basis.
References

1. S.Suga and C.Tusche, Photoelectron spectroscopy in a wide hn 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).
紹介教員：岩佐 義宏 教授、石坂香子 准教授