Element-Specific Orbital Character in a Nearly-Free-Electron Superconductor Ag${}_5$Pb${}_2$O${}_6$ Revealed by Core-Level Photoemission

Abstract

Ag${}_5$Pb${}_2$O${}_6$ has attracted considerable attention due to its novel nearly-free-electron superconductivity, but its electronic structure and orbital character of the Cooper-pair electrons remain controversial. Here, we present a method utilizing core-level photoemission to show that Pb 6$s$ electrons dominate near the Fermi level. We observe a strongly asymmetric Pb 4$f_{7/2}$ core-level spectrum, while a Ag 3$d_{5/2}$ spectrum is well explained by two symmetric peaks. The asymmetry in the Pb 4$f_{7/2}$ spectrum originates from the local attractive interaction between conducting Pb 6$s$ electrons and a Pb 4$f_{7/2}$ core hole, which implies a dominant Pb 6$s$ contribution to the metallic conduction. In addition, the observed Pb 4$f_{7/2}$ spectrum is not explained by the well-known Doniach-Šunjić lineshape for a simple metal. The spectrum is successfully generated by employing a Pb 6$s$ partial density of states from local density approximation calculations, thus confirming the Pb 6$s$ dominant character and free-electron-like density of states of Ag${}_5$Pb${}_2$O${}_6$.

8 pages, 5 figures

References in corpus (5)

• The crystal structure of FeSe0.44Te0.56
• Exceptional type-I superconductivity of the layered silver oxide Ag${}_5$Pb${}_2$O${}_6$
• Non-linear Temperature Dependence of Resistivity in Single Crystalline Ag${}_5$Pb${}_2$O${}_6$
• Nearly free electrons in the layered oxide superconductor Ag5Pb2O6
• Electronic band structure and Fermi surface of Ag${}_5$Pb${}_2$O${}_6$