Nanotechnologies / Materials
Nanotechnologies, Smart devices

Investigation of novel physical properties of atomic layer crystals: fundamental research for creating next-generation quantum devices
Department of Applied Physics, Graduate School of Engineering
Professor Kazuyuki Sakamoto
Researchmap https://researchmap.jp/read0184558?lang=en

Abstract

which is essential for next-generation devices.

Nanotechnologies / Materials

Two-dimensional atomic layer materials with a thickness of one
to a few atoms, which are the thinnest materials possible, exhibit
physical phenomena not seen in three-dimensional solids, andthese phenomena can be used to create completely new devices.
In order to further develop the basic scientific knowledge and applications of these materials, we have created "atomic layer crystals," i.e., materials that do not exist in nature, on solid surfaces,
and have investigated the origin of their novel physical phenomena. We are also developing methods to control the novel physicalproperties of atomic layer crystals by adsorbing different atoms
and molecules onto them and also by photoirradiation.

▍ Background & Results
Electron spins appearing in nonmagnetic atomic layer crystals
were thought to originate from the asymmetric density of electrons
around the nucleus, and their orientation was thought to be perpendicular to the atomic layer plane and the direction of motion.
This can be thought of as being similar to Fleming's left-hand rule.
Although electron spins in different directions have also beenobserved, they have been explained by different reasons and nouniversal understanding has been obtained so far. Since electron
spins in atomic layer crystals play a fundamental role in the operation of quantum devices, elucidation of their origin and control
methods is indispensable for the construction of next-generation
highly functional quantum devices. Our recent experimental results
show that the orientation of all electron spins is due to the orbital motion of electrons. This means that the direction of electron
spins can be thought of not as Fleming's left-hand rule, but as aright-handed screw rule. This kind of spin motion originating fromthe orbital motion of electrons is a completely new mechanism thathas not been considered before, and it means that if the orbital
motion of electrons can be freely designed, the spin direction canbe arbitrarily changed. We have also succeeded in controlling thephysical properties of such atomic layer crystals by the adsorptionof organic molecules or, by photo-irradiation, in the case of topological insulators where electron spins similar to those of atomic
layer crystals appear.

▍ Significance of the research and Future perspective
In order to cope with the explosive increase in the amount of
information and its processing, which is an urgent issue in themodern society, it is essential to create quantum devices with highprocessing speed, long lifetime, and drastically reduced power
consumption. Redesigning devices based on atomic layer crystals
can greatly improve the device performance, but to do so, it is essential to first understand the fundamental quantum properties ofthese materials. This research will not only open up a new field ofbasic science on the physical properties of atomic layer crystals,
but also create quantum materials with highly efficient spin currents

P a t e n t

１2. ご自身の顔写真のご提供

Kobayashi, Takahiro; Nakata, Yoshitaka; Yaji, Koichiro et al. Orbital angular※
momentum
induced spin polarization of 2D metallic bands. Phys. Rev. Lett.
印刷可能な解像度のものを電子ファイルにてご提供ください。
2010 Oct 22; 105(17): 176401. doi: 10.1103/PhysRevLett.125.176401
Sakamoto, Kazuyuki; Ishikawa, Hirotaka; Wake, Takashi et al. Spatial Control of Charge Doping in n-Type Topological Insulators. Nano Lett. 2021 May 26;
21(10): 4415-4422. doi: 10.1021/acs.nanolett.1c01100
UR
L http://snp.ap.eng.osaka-u.ac.jp
K e y w o r d atomic layer crystals, electronic states, electron spin, rashba-edelstein effect, photoelectron spectroscopy
Tr e a t i s e