Emergence of Orbital Angular Momentum by Inversion Symmetry Breaking and Its Detection by ARPES

TL;DR

This paper demonstrates that inversion symmetry breaking induces a chiral orbital angular momentum in surface bands, detectable via ARPES, even without spin-orbit interaction, and introduces the concept of an orbital Galvanic effect.

Contribution

It reveals the emergence of orbital angular momentum-momentum correspondence due to inversion symmetry breaking and proposes a novel ARPES-based detection method.

Findings

Chiral orbital angular momentum observed on Cu surface

Orbital angular momentum exists without spin-orbit coupling

Proposed and confirmed CD-ARPES detection method

Abstract

Rashba-split surface band is characterized by a one-to-one correspondence between the electron's momentum k and its spin orientation. Here we show that a similar correspondence between momentum and orbital angular momentum (OAM) must exist on surface bands once the inversion symmetry is broken. The correspondence is valid even when there is no spin-orbit interaction. Tight-binding and first-principles calculations are presented to support our claim. As a method to detect such OAM-momentum correspondence, we propose the circular dichroism (CD) experiment using the angle-resolved photoemission (ARPES) setup. CD-ARPES experiment performed on Cu surface confirms the existence of chiral OAM. A new concept of "orbital Galvanic effect" is proposed.