| Pacific Rim Symposium on Surfaces, Coatings and Interfaces (PacSurf 2014) | |
| Thin Films | Monday Sessions |
| Session TF-MoE |
| Session: | Electronics and Displays on Flexible and Hard Substrates |
| Presenter: | Shuji Hasegawa, University of Tokyo, Japan |
| Authors: | S. Hasegawa, University of Tokyo, Japan N. Fukui, University of Tokyo, Japan R. Hobara, University of Tokyo, Japan T. Hirahara, Tokyo Institute of Technology, Japan A. Takayama, University of Tokyo, Japan |
| Correspondent: | Click to Email |
Recent studies have shown that the surface states exhibit spin-split and spin helical structures when spin-orbit coupling is strong enough. This is due to break down of space-inversion symmetry at crystal surfaces. Surface Rashba systems and topological insulators (TI) are the typical examples. This causes interesting phenomena relating to flow of spins, such as spin-polarized current [1] and spin current (without charge current) at crystal surfaces and edges of thin atomic layers of such materials. Such spin current may be useful for future spintronics devices because spin current causes no energy dissipation.
“Spin Hall Effect” (SHE) is one of such phenomena, which produces spin current perpendicular to the charge current. Due to bending of electron flow in opposite directions depending on the spin orientation, caused by strong spin-orbit coupling, a flow of spin is produced in the direction perpendicular to the charge current. Its time-reversal process also occurs (inverse SHE) in which the spin current produces charge current, by which we can detect he effects.
By using a H-shaped pattern of thin Bi2Se3 film, one of the topological insulators, we have tried to detect the SHE. The pattern was fabricated in a UHV-FIB (Focused Ion Beam) combined with a four-tip STM and MBE chambers [2]. In order to verify the SHE, we measured the nonlocal voltage drop caused by SHE and inverse SHE. All the processes including the film growth, patterning and measurements were done in situ in UHV to protect the surface states with a four-tip STM equipped with FIB [2]. The nonlocal voltage drop obtained was mainly explained by the classical Ohm’s law, with small deviation. The deviation is explained by the SHE. From the data fitting we could deduced the spin-Hall angle and spin relaxation length.
[1] T. Tono, et al., New J. Phys. 15, 105018 (2013).
[2] N. Fukui et al., e-J. Surf. Sci. Nanotech., submitted.