BCS-Like Bogoliubov Quasiparticles in High-TcSuperconductors Observed by Angle-Resolved Photoemission Spectroscopy

Abstract

We performed high-resolution angle-resolved photoemission spectroscopy on triple-layered high-$T_c$ cuprate ${\mathrm{B}\mathrm{i}}_2{\mathrm{S}\mathrm{r}}_2{\mathrm{C}\mathrm{a}}_2{\mathrm{C}\mathrm{u}}_3{\mathrm{O}}_{10+\delta }$. We have observed the full energy dispersion (electron and hole branches) of Bogoliubov quasiparticles and determined the coherence factors above and below $E_F$ as a function of momentum from the spectral intensity as well as from the energy dispersion based on BCS theory. The good quantitative agreement between the experiment and the theoretical prediction suggests the basic validity of BCS formalism in describing the superconducting state of cuprates.