Momentum-dependent light scattering in a two-dimensional Heisenberg antiferromagnet: Analysis of x-ray scattering data

Abstract

Motivated by the achievements of the x-ray scattering technique, we analyzed the profile of the light scattering cross section $R(q,\ensuremath{\omega})$ at a finite $q$ in a 2D Heisenberg antiferromagnet. Previous Raman scattering studies at $q=0$ identified the two-magnon peak in ${B}_{1g}$ scattering geometry. We found that the ${B}_{1g}$ peak disperses downwards at a finite $q$, and its cross section increases, reaching its maximum at $q={q}_{0}=(0,\ensuremath{\pi})$ and symmetry related points. In addition, the cross-section in the ${A}_{1g}$ geometry becomes nonzero at a finite $q$, and also displays a two-magnon peak which gains strength and disperses to larger frequencies with increasing $q$, and reaches its highest cross section at ${q}_{0}$. We found that the profile of $R({q}_{0},\ensuremath{\omega})$ is equivalent in ${A}_{1g}$ and ${B}_{1g}$ geometries.