杂化能带与电子-声子耦合的本征上限

本文用角动量分波表象的能带论方法研究了杂化导带的一般性质。得出了电子态密度和分波含量的一般关系式。发现引用一个径向波函数φ_l的“相位函数”y_l,可以方便地对球对称势场造成的相移和φ_l的对数微商作解析近似处理。在此基础上研究了电子-声子耦合中的系数η的性质。论证了η有一个“本征上限”,并估计了它的量级。讨论了影响η强弱的一般规律,与实验现象作了比较。指出提高导带角动量杂化程度,特别是提高d导带中的f分波含量,以至试图实现似f导带,可能是强化电子-声子耦合潜力较大的探索方向。 关键词：

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 |B_li^k|² were derived. Introducing a "phase function" y_l which corresponds to a certain radial wave function φ_l, it permits one to derive an analytical approximation for the logarithmic derivative of φ_l 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 T_c, we emphasized the role of magnitude of hybridization, especilly enhancing the f-component in a d-like conduction band.