Superconducting energy gap in Bi2Sr2CaCu2O8 observed by high-resolution photoemission spectroscopy

Abstract

A high-energy resolved low-temperature photoemission spectrometer of angle-integrated mode was constructed to study the detailed electronic structure near the Fermi level of novel materials, in particular, cuprate high-Tc superconductors. Photoemission measurement with this spectrometer on a Bi2Sr2CaCu2O8 polycrystal clearly showed a transfer of spectral weight from the vicinity of the Fermi level to the higher binding-energy region below the superconducting transition temperature, indicating opening of the superconducting gap. Numerical simulation for both normal and superconducting states showed that the superconducting gap parameter (Δ) of 18 meV with dx 2−y 2 symmetry gives a most reasonable fitting.