When 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. As a proof of principle, we show from first principles that this effect leads to chiral orbital textures in k-space of the BiAg2 monolayer. In predicting the magnitude of the orbital moment arising from the orbital Rashba effect, we demonstrate the crucial role that the Berry phase theory plays 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.
@article{arxiv.1611.04674,
title = {Surface orbitronics: new twists from orbital Rashba physics},
author = {Dongwook Go and Jan-Philipp Hanke and Patrick M. Buhl and Frank Freimuth and Gustav Bihlmayer and Hyun-Woo Lee and Yuriy Mokrousov and Stefan Blügel},
journal= {arXiv preprint arXiv:1611.04674},
year = {2017}
}