ON HYBRIDIZED BAND AND THE INTRINSIC UPPER LIMIT OF ELECTRON-PHONON COUPLING

The general properties of hybridized conduction bands were studied in the LMTO representation. General expressions of the density of states N(E) and partial wei-ghts |Blik|2 were derived. Introducing a "phase function" yl which corresponds to a certain radial wave function φl, it permits one to derive an analytical approximation for the logarithmic derivative of φl and the phase shift due to a spherically symmetrical potential. Then the analytical behaviour of electronic factor η in electron-phonon coupling was studied. We verified the presence of an "intrinsic upper limit" for η and evaluated its order of magnitude. Discussions were given for the general rules affecting η and the comparison with experiment. As for the relation to searching for strong coupling and high Tc, we emphasized the role of magnitude of hybridization, especilly enhancing the f-component in a d-like conduction band.