Resonant Inelastic X-Ray Scattering as a Probe of the Phase and Excitations of the Order Parameter of Superconductors

TL;DR

This paper develops a theoretical framework for using resonant inelastic x-ray scattering (RIXS) to investigate the phase, pairing symmetry, and elementary excitations of superconductors, highlighting its potential as a diagnostic tool.

Contribution

The paper introduces a scattering theory for RIXS in superconductors, demonstrating how it can distinguish pairing symmetries and probe excitations based on the superconducting gap.

Findings

RIXS scattering amplitude depends on pairing symmetry and gap.

Low-energy RIXS signals are influenced by coherence factors.

RIXS can differentiate between various unconventional superconducting states.

Abstract

The capability to probe the dispersion of elementary spin, charge, orbital, and lattice excitations has positioned resonant inelastic x-ray scattering (RIXS) at the forefront of photon science. Here we develop the scattering theory for RIXS on superconductors, calculating its momentum-dependent scattering amplitude. Considering superconductors with different pairing symmetries, we show that the low-energy scattering is strongly affected by the superconducting gap and coherence factors. This establishes RIXS as a tool to disentangle pairing symmetries and to probe the elementary excitations of unconventional superconductors.