Two-dimensional folding technique for enhancing Fermi surface signatures in the momentum density: Application to Compton scattering data from an Al-3 at. % Li disordered alloy

Abstract

We present a technique for enhancing Fermi surface ͑FS͒ signatures in the two-dimensional ͑2D͒ distribution obtained after the 3D momentum density in a crystal is projected along a specific direction in momentum space. These results are useful for investigating fermiology via high-resolution Compton scattering and positron annihilation spectroscopies. We focus on the particular case of the ͑110͒ projection in a fcc crystal where the standard approach based on the use of the Lock-Crisp-West ͑LCW͒ folding theorem fails to give a clear FS image due to the strong overlap with FS images obtained through projection from higher Brillouin zones. We show how these superposed FS images can be disentangled by using a selected set of reciprocal lattice vectors in the folding process. The applicability of our partial folding scheme is illustrated by considering Compton spectra from an Al-3 at. % Li disordered alloy single crystal. For this purpose, high-resolution Compton profiles along nine directions in the ͑110͒ plane were measured. Corresponding highly accurate theoretical profiles in Al-3 at. % Li were computed within the local density approximation ͑LDA͒-based Korringa-KohnRostoker coherent potential approximation ͑KKR-CPA͒ first-principles framework. A good level of overall accord between theory and experiment is obtained, some expected discrepancies reflecting electron correlation effects notwithstanding, and the partial folding scheme is shown to yield a clear FS image in the ͑110͒ plane in Al-3 at. % Li.

Magnetic momentum density, Fermi surface, and directional magnetic Compton profiles inLaSr2Mn2O7andMijnarends1, Kaprzyk2, Barbiellini3 et al. 2007Phys. Rev. BSelf Cite

“…(2) the momentum density is not only determined by the occupation function but also by the wavefunction transforms, we investigate in the following section how the interplay between FS and wavefunctions affects the observability of various FS sheets. The complete Fermi surface can in principle be mapped without the interference of wavefunction effects by performing a 2D-or 3D-reconstruction of the momentum density followed by Lock-Crisp-West folding as described by Matsumoto et al 46 for Al-3at.% Li alloys. In this way, one can transform the momentum density in p space to an occupation number density in k space.…”

Electronic structure of Mg studied by Compton scattering

“…Now, instead of reconstructing r(p) from 1D spectra, one can restrict analysis to calculating r l ( p x , p y ), as was applied with success in papers [3][4][5][6][7][8][9][10][11].…”

Experimental determination of the PdH0.84 Fermi surface

“…But, usually, the breaks are not clear because of the double integration J(p z ). Alternatively, ρ(p) was obtained by the direct Fourier method from CPs along different scattering directions: [13][14][15] We define the reciprocal form factor.…”

“…periment [12][13][14][15]. The Compton scattering method has more advantages than other methods for observing the electronic structure of metal hydrides.…”