Abstract
The nearly-free-electron (NFE) pseudopotential theory is used to calculate the wave-vector-dependent plasmon linewidth due to interband transitions in lithium, sodium, and potassium. It is shown that interband excitations constitute the dominant decay mechanism which for all alkali metals results in a decreasing linewidth for small , contrary to a recent model calculation by Gibbons. Together with estimates of contributions from two particlehole pair excitations and from phonon- and impurity-assisted intraband and interband transitions, the resulting linewidth is compared with experiment. In Li, the total linewidth decreases for , as borne out by experiment, whereas for Na and K the contribution from pair-pair excitations leads finally to an increasing linewidth, in qualitative agreement with experiment. Remaining quantitative discrepancies suggest that interband transitions to empty bands beyond the NFE model contribute to the plasmon linewidth in K and possibly also in Na.
- Received 19 February 1981
DOI:https://doi.org/10.1103/PhysRevB.24.3054
©1981 American Physical Society