Single-Domain Orbital Angular Momentum Mapping: Advancing Photoemission Dichroism to the Nanoscale

Abstract

Abstract Circular dichroism in angle-resolved photoemission spectroscopy (CD-ARPES) is widely used to probe orbital angular momentum (OAM) and Berry-curvature-related phenomena in two-dimensional quantum materials. However, in many materials, conventional micron-scale measurements often average over domains with opposite OAM polarization, canceling intrinsic dichroic signals and leaving spectra dominated by extrinsic asymmetries arising from photoelectron final-state interference. Here, we combine circularly polarized light with NanoARPES to achieve spatially resolved CD-ARPES with sub-800 nm resolution. By isolating individual domains, this approach enables direct access to the intrinsic OAM texture. As a model system, we investigate the K/K′ point valley states of the quantum spin Hall insulator indenene─a triangular indium monolayer epitaxially grown on SiC(0001)─where substrate-induced terraces host alternating valley configurations whose dichroic response is averaged out in conventional measurements. Terrace-resolved NanoARPES disentangles these contributions, allowing direct visualization of oppositely polarized domains and revealing the OAM texture associated with a topological band inversion. Our results establish spatially resolved CD-ARPES as a robust approach for isolating intrinsic OAM contrast by eliminating domain averaging and correcting for extrinsic geometry-dependent contributions. This enables direct access to the Berry curvature near the Fermi level, providing a powerful probe of the system’s intrinsic topological character.

The authors' abstract, as published at the source. ACS Nano, 2026 · DOI ↗