Electrons and Phonons in YbC6

TL;DR

This study combines theoretical density functional calculations and experimental photoemission to analyze the electronic structure and phonons in YbC6, revealing hybridized Yb f states and their potential role in superconductivity.

Contribution

It provides a detailed theoretical and experimental analysis of YbC6's electronic structure, showing fully occupied Yb f states and their hybridization, which was not previously well understood.

Findings

Yb f states are fully occupied with no mixed-valent behavior

Yb f states hybridize with Yb 5d and C 2p states

Soft Yb phonons may contribute to superconductivity

Abstract

The electronic structure and selected zone-center phonons in Yb graphite intercalation compound (YbC6) are investigated {theoretically} using density functional calculations and LDA+U approximation for Coulomb correlations in the f shell, and experimentally using angle-resolved photoemission. We find that both in LDA and LDA+U approach the Yb f states are fully occupied providing no evidence for mixed-valent behavior. The obtained theoretical results are in good agreement with photoemission experiments. The 4f states are considerably hybridized both with the Yb 5d and C 2p states resulting in a substantial admixture of Yb f at the Fermi level. Soft Yb phonons, given a noticeable presence of the Yb states at the Fermi level, are probably responsible for the superconductivity recently reported in YbC6.