Spin Dynamics and Resonant Inelastic X-ray Scattering in Chromium with Commensurate Spin-Density Wave Order

TL;DR

This paper theoretically studies spin dynamics and RIXS spectra in Chromium with SDW order, revealing the persistence of spin-wave excitations up to 0.6 eV and discussing their detectability in RIXS experiments.

Contribution

It provides a detailed theoretical analysis of spin excitations and RIXS spectra in Chromium with SDW order, highlighting differences from neutron scattering and potential experimental detection.

Findings

Spin-wave excitations persist up to ~0.6 eV without damping.

RIXS spectra show broad spectral weight from particle-hole excitations.

Detection of spin-waves in RIXS depends on experimental resolution.

Abstract

We theoretically investigate spin dynamics and $L_3$-edge resonant inelastic X-ray scattering (RIXS) of Chromium with commensurate spin-density wave (SDW) order, based on a multi-band Hubbard model composed of 3$d$ and 4$s$ orbitals. Obtaining the ground state with the SDW mean-field approximation, we calculate the dynamical transverse and longitudinal spin susceptibility by using random-phase approximation. We find that a collective spin-wave excitation seen in inelastic neutron scattering hardly damps up to $\sim$0.6 eV. Above the energy, the excitation overlaps individual particle-hole excitations as expected, leading to broad spectral weight. On the other hand, the collective spin-wave excitation in RIXS spectra has a tendency to be masked by large spectral weight coming from particle-hole excitations with various orbital channels. This is in contrast with inelastic neutron scattering, where only selected diagonal orbital channels contribute to the spectral weight. However, it may be possible to detect the spin-wave excitation in RIXS experiments in the future if resolution is high enough.