Surface orbitronics: new twists from orbital Rashba physics

TL;DR

This paper introduces the orbital Rashba effect at surfaces, driven by sp orbital hybridization, leading to chiral orbital textures and potential applications in surface orbitronics, supported by first-principles calculations.

Contribution

It proposes a new mechanism for the orbital Rashba effect based on orbital hybridization, expanding the understanding of surface orbital phenomena without relying on spin-orbit coupling.

Findings

Demonstrates chiral orbital textures in BiAg₂ monolayer

Highlights the role of Berry phase in orbital texture magnitude

Predicts significant orbital effects at surfaces

Abstract

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 $\mathbf{k}$-space of the BiAg$_2$ 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.