Physics (Internal)

Probing nodal point singularities using resonant inelastic X-ray scattering

This event is part of the Departmental Seminars.

In this talk I will discuss a recent work of ours, in which we worked out the theory of resonant inelastic x-ray scattering (RIXS) of electronic excitations in topological nodal-point semimetals. RIXS is a one photon in - one photon process which imparts both energy and momentum to the material, effectively causing particle hole excitations across the Fermi level. We derived the general cross-section for RIXS in band structures in the fast collision approximation, elucidating the effects of symmetry and atomic form factors. Spectral patterns in the geometry and intensity of the RIXS response reveal the presence of nodal points in the band structure. To demonstrate this, we first calculated analytically the geometry and functional form of the particle-hole continuum of Weyl nodes, encapsulated in the energy-resolved joint density of states. We then performed an exact calculation of the RIXS intensity for a nodal point observed in transition-metal monosilicides, using the band structure determined by density functional theory. We found that the RIXS spectrum contains the characteristics of the particle-hole continuum of nodal points and can thus be used to identify them. We concluded that RIXS can detect signatures of topological origin in the three-dimensional band structures of materials and is especially pertinent in settings that are inaccessible to ARPES, such as for unoccupied bands and in magnetic fields. This paves the way for RIXS as a robust technique for studying band excitations in future experiments.

ZOOM: https://bostonu.zoom.us/j/94633829536?pwd=bFhOdlRXVWY4OC9RSmxvdHA3VGNRZz09