Probing magnetic orbitals and Berry curvature with circular dichroism in resonant inelastic X-ray scattering

TL;DR

This paper demonstrates how circular dichroism in resonant inelastic X-ray scattering (RIXS) can be used to probe magnetic orbitals and Berry curvature in quantum materials, providing a new experimental approach to study topological states.

Contribution

It introduces a method to extract orbital angular momentum textures from dichroic RIXS spectra, linking optical selection rules to quantum geometric properties in materials.

Findings

Simulated dichroic RIXS spectra for MoSe₂ and 1T'-MoS₂ show detectable signals.

Established the connection between OAM textures and RIXS dichroism.

Provided guidelines for experimental observation of Berry curvature via RIXS.

Abstract

Resonant inelastic X-ray scattering (RIXS) can probe localized excitations at selected atoms in materials, including particle-hole transitions between the valence and conduction bands. These transitions are governed by fundamental properties of the corresponding Bloch wave-functions, including orbital and magnetic degrees of freedom, and quantum geometric properties such as the Berry curvature. In particular, orbital angular momentum (OAM), which is closely linked to the Berry curvature, can exhibit a nontrivial momentum dependence. We demonstrate how information on such OAM textures can be extracted from the circular dichroism in RIXS. Based on accurate modeling with first-principles treatment of the key ingredient -- the light-matter interaction -- we simulate dichroic RIXS spectra for the prototypical transition metal dichalcogenide MoSe$_2$ and the two-dimensional topological insulator 1T$^\prime$-MoS$_2$. Guided by an intuitive picture for the optical selection rules, we discuss how the momentum-dependent OAM manifests itself in the dichroic RIXS signal if one controls the momentum transfer. Our calculations are performed for typical experimental geometries and parameter regimes, and demonstrate the possibility of observing the predicted circular dichroism in forthcoming experiments. Thus, our work establishes a new avenue to observing Berry curvature and topological states in quantum materials.