# Resonant inelastic x-ray incarnation of Young's double-slit experiment

## TL;DR

This paper demonstrates that resonant inelastic x-ray scattering (RIXS) can produce interference patterns akin to Young's double-slit experiment, revealing the symmetry and nature of electronic excited states in complex materials.

## Contribution

It introduces a novel inelastic scattering analogue of Young's double-slit experiment using RIXS to probe electronic excitations and their symmetries in solids.

## Key findings

- RIXS interference patterns reveal electronic state symmetries.
- Demonstrated in Ba3CeIr2O9 with Ir dimers.
- Shows potential for studying complex superstructures.

## Abstract

Young's archetypal double-slit experiment forms the basis for modern diffraction techniques: the elastic scattering of waves yields an interference pattern that captures the real-space structure. Here, we report on an inelastic incarnation of Young's experiment and demonstrate that resonant inelastic x-ray scattering (RIXS) measures interference patterns which reveal the symmetry and character of electronic excited states in the same way as elastic scattering does for the ground state. A prototypical example is provided by the quasi-molecular electronic structure of insulating Ba3CeIr2O9 with structural Ir dimers and strong spin-orbit coupling. The double 'slits' in this resonant experiment are the highly localized core levels of the two Ir atoms within a dimer. The clear double-slit-type sinusoidal interference patterns that we observe allow us to characterize the electronic excitations, demonstrating the power of RIXS interferometry to unravel the electronic structure of solids containing, e.g., dimers, trimers, ladders, or other superstructures.