Electron-Positron Enhancement in d-Metals Described by the Bloch-Modified Ladder Theory and the Local Density Approximation: a Comparative Study

H. Sormann and D. Wallner Institut für Kernphysik, Technische Universität Graz, Petersgasse 16, 8010 Graz, Austria

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In this paper, we present a preliminary summary of our recent results on the enhancement of the electron-positron annihilation rate in d-band metals based on our recently published optimized quasi-free Bloch-modified ladder [QF-BML(opt.)] theory. This approach enables us to investigate the influence of the periodical lattice potential on the electron-positron annihilation in an approximative but nevertheless physically reasonable way. We used our theory for calculations of momentum-dependent enhancement factors belonging to electron states of different (s-, p-, d-) character in simple, transition and noble metals (Na, Cu, Pd, V). It is interesting to compare these new BML results with corresponding results obtained by the local density approximation (LDA) according to the work of Daniuk et al. We observe relatively strong differences between the BML and LDA enhancement factors for metals whose polarization process is dominated by s or p electrons. In such cases, we presume that the LDA approach has the tendency to overestimate the role of the more-localized d electrons in the polarization of the inhomogeneous electron gas. For transition metals whose physics is mainly determined by such d electrons, the discrepancies between BML and LDA enhancement results are significantly smaller.

DOI: 10.12693/APhysPolA.88.225 PACS numbers: 78.70.Bj, 71.25.Pi