Momentum density spectroscopy of Pd: Comparison of 2D-ACAR and Compton scattering using a 1D-to-2D reconstruction method

Abstract

Two-dimensional (2D) angular correlation of annihilation radiation and Compton scattering are both powerful techniques to investigate the bulk electronic structure of crystalline solids through the momentum density of the electrons. Here we apply both methods to a single crystal of Pd to study the electron momentum density and the occupancy in the first Brillouin zone and to point out the complementary nature of the two techniques. To retrieve the 2D spectra from one-dimensional Compton profiles, a direct inversion method is implemented and benchmarked against the well-established Cormack's method. The comparison of experimental spectra with first-principles density functional theory calculations of the electron momentum density and the two photon momentum density clearly reveals the importance of positron probing effects on the determination of the electronic structure. While the calculations are in good agreement with the experimental data, our results highlight some significant discrepancies.

L -hole pockets of the Fermi surface of palladium revealed by positron annihilation spectroscopy

“…), however, is significantly better than the values reported in Ref. [72] (0.17 and 0.21 a.u.). The inferior experiment resolution reported in Ref.…”

“…The inferior experiment resolution reported in Ref. [72] is due to the spectrometer's relatively short detector-detector distance. The EMD (lower-left quadrants).…”

“…In a recent paper [72] the differences between the momentum distributions observed by positron annihilation and Compton scattering were investigated. The focus of that study was a new approach for tomographical reconstruction of 2D electron momentum distributions from the 1D Compton profiles rather than observing the impact of electron correlation and relativistic effects on electronic structure of Pd and its Fermi surface.…”

Ab initio study of the electronic states of V3Si in momentum space

“…Observing the annihilation radiation provides information about the electronic structure in the momentum space. 29,39,40 This can be calculated from the squared absolute value of the Fourier transform of the wave function of electrons ψ k n ( r ) and positrons function ψ p ( r ) denoted here as ρ 2 γ ( p ). In the independent particle approximation:where γ ( r ) is the enhancement factor and it has a large effect on the annihilation rate.…”

$L$-hole Pockets of the Palladium Fermi Surface Revealed by Positron Annihilation Spectroscopy

“…The inferior experiment resolution reported in Ref. 72 is due to the spectrometer's relatively short detector-detector distance.…”