Observation of spin-free interatomic orbital angular momentum in a chiral crystal

TL;DR

This paper demonstrates the existence of spin-free interatomic orbital angular momentum in a chiral crystal, revealing pure orbital currents and advancing the field of orbitronics.

Contribution

It introduces a novel approach to realize spin-decoupled orbital angular momentum states in crystalline solids using ARPES and first-principles calculations.

Findings

Resolved well-isolated s-orbital bands in a chiral Te crystal

Confirmed OAM arising solely from interatomic hopping

Established absence of spin angular momentum in these states

Abstract

The inherent spin-orbit interaction of electrons inevitably couples spin to the orbital angular momentum (OAM), posing a fundamental challenge to spin-free orbital transport. Here, we propose a novel strategy to achieve spin-decoupled OAM states in crystalline solids. Using angle-resolved photoemission spectroscopy (ARPES), we resolve well-isolated s-orbital bands in a chiral Te crystal, clearly separated from the p-orbital manifold. Combined circular dichroism ARPES and first-principles calculations reveal that these bands host OAM arising exclusively from interatomic hopping, with no intra-atomic contribution. Spin-resolved ARPES further confirms the absence of SAM, providing decisive evidence of spin-free OAM states. These findings establish the existence of OAM without spin polarization in crystalline solids and highlight the essential role of inter-atomic OAM. This work provides a general framework for designing spinless OAM states, opening an opportunity toward pure orbital currents for orbitronics.