Context of project
At interfaces and surfaces the spatial inversion symmetry breaking induces a momentum dependent splitting of spin sub-bands in condensed matter systems. This effect is better known nowadays as "Rashba effect" [1, 2]. Although this effect is the collective result of spin orbit interaction and asymmetry in the crystal potential, it is said that systems which present "Rashba effect" have spin orbit coupling of the Rashba type. One consequence of the Rashba spin orbit coupling is the possibility of converting electrical current to spin current and vice-versa, this is known as the Edelstein effect [3]. The spin current is a flow of angular momentum, which can be generated by the so-called spin pumping, where a given magnetization in a ferromagnetic material precess under a resonant condition (ferromagnetic resonance). In this research project we use the circular polarization of light (or helicity) as source of angular momentum. We couple the light to diverse material systems with Rashba spin orbit coupling and study the generated photovoltage/photocurrent due to the spin to charge conversion mechanism. Currently, at our lab facilities we can do experiments in the optical energy range from 1.1 eV to 3.05 eV, at normal incidence and oblique angles up to 75 deg. Rashba effect references: [1] www.jetpletters.ac.ru/ps/1264/article_19121.shtml [2] iopscience.iop.org/1367-2630/17/5/050202/media/njp050202_suppdata.pdf Edelstein effect reference: [3] www.sciencedirect.com/science/article/abs/pii/003810989090963C Our work We have recently demonstrated the modulation of photovoltage at the Cu/Bi2O3 interface due to spin to charge conversion. Interestingly, even though the Rashba spin orbit coupling was not expected to induced drastic distortion of the electronic bands beyond the splitting of spin sub-bands, in our experiments we detect significant spin to charge conversion above the Fermi level and well-below the band gap of Bi2O3. Our photovoltaic experiments together with density functional theory demonstrates that spin orbit coupling can significantly distort locally the electronic band structure, and in fact, allow new paths for efficient optical absorption with spin information. Read more: Photoinduced Rashba Spin-to-Charge Conversion via an Interfacial Unoccupied State J. Puebla, F. Auvray, N. Yamaguchi, M. Xu, S.Z. Bisri, Y. Iwasa, F. Ishii, Y. Otani Physical review letters 122 (25), 256401 (2019) journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.256401 arXiv: https://arxiv.org/abs/1902.00237 Highlights: www.riken.jp/en/news_pubs/research_news/rr/20190830_FY20190022/index.html Personal contribution: Project leader (corresponding author), proposed project, analyzed data, writing of manuscript
0 Comments
Leave a Reply. |
Jorge PueblaResearch Scientist Archives
October 2020
Categories |