Plasmon Lifetime in K A Case Study of Correlated Electrons in Solids Amenable to Ab Initio.pdfVIP

Plasmon Lifetime in K: A Case Study of Correlated Electrons in Solids Amenable to Ab Initio Theory Wei Ku and Adolfo G. Eguiluz Department of Physics and Astronomy, The University of Tennessee, Knoxville, TN 37996-1200 and Solid State Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6030 Abstract On the basis of a new ab initio, all-electron response scheme, formulated within time- dependent density-functional theory, we solve the puzzle posed by the anomalous dispersion of the plasmon linewidth in K. The key damping mechanism is shown to be decay into particle- hole pairs involving empty states of d-symmetry. While the effect of many-particle correlations is small, the correlations built into the “final-state” d-bands play an important, and novel, role —which is related to the phase-space complexity associated with these flat bands. Our case study of plasmon lifetime in K illustrates the importance of ab initio paradigms for the study of excitations in correlated-electron systems. Much less is known about how to calculate accurate lifetimes of electronic excitations for realistic models of solids than about ground-state and structural properties of these systems. Currently a maj or thrust is focused on the excitations (involving spin, charge, phononic degrees of freedom, etc.) in systems of strongly-correlated electrons. The complex band structure characteristic of these systems notwithstanding, the prevalent paradigm adopted for their study invokes sophisticated treatments of correlation together with minimal representations of the band structure [1]. Interestingly, for systems with simpler band structures the puzzles posed by a variety of spectroscopic data [2,3] have led to the advocacy of a similar paradigm. This being the case, the