Go Dongwook, Hanke Jan-Philipp, Buhl Patrick M, Freimuth Frank, Bihlmayer Gustav, Lee Hyun-Woo, Mokrousov Yuriy, Blügel Stefan
Peter Grünberg Institut and Institute of Advanced Simulation, Forschungszentrum Jülich and JARA, 52425 Jülich, Germany.
Department of Physics, Pohang University of Science and Technology, Pohang 37673, Korea.
Sci Rep. 2017 Apr 25;7:46742. doi: 10.1038/srep46742.
As the inversion symmetry is broken at a surface, spin-orbit interaction gives rise to spin-dependent energy shifts - a phenomenon which is known as the spin Rashba effect. Recently, it has been recognized that an orbital counterpart of the spin Rashba effect - the orbital Rashba effect - can be realized at surfaces even without spin-orbit coupling. Here, we propose a mechanism for the orbital Rashba effect based on sp orbital hybridization, which ultimately leads to the electric polarization of surface states. For the experimentally well-studied system of a BiAg monolayer, as a proof of principle, we show from first principles that this effect leads to chiral orbital textures in k-space. In predicting the magnitude of the orbital moment arising from the orbital Rashba effect, we demonstrate the crucial role played by the Berry phase theory for the magnitude and variation of the orbital textures. As a result, we predict a pronounced manifestation of various orbital effects at surfaces, and proclaim the orbital Rashba effect to be a key platform for surface orbitronics.
由于表面处的反演对称性被打破，自旋 - 轨道相互作用会导致与自旋相关的能量偏移——这一现象被称为自旋 Rashba 效应。最近，人们认识到自旋 Rashba 效应的轨道对应物——轨道 Rashba 效应——即使在没有自旋 - 轨道耦合的情况下也能在表面实现。在此，我们提出一种基于 sp 轨道杂化的轨道 Rashba 效应机制，这最终会导致表面态的电极化。对于实验上已充分研究的 BiAg 单层系统，作为原理证明，我们从第一性原理表明，这种效应会在 k 空间中导致手性轨道纹理。在预测由轨道 Rashba 效应产生的轨道磁矩大小时，我们证明了 Berry 相理论对轨道纹理的大小和变化所起的关键作用。结果，我们预测表面会出现各种明显的轨道效应，并宣称轨道 Rashba 效应是表面轨道电子学的关键平台。
