Angle-resolved photoemission spectroscopy study of the superconducting gap anisotropy in Bi2Sr2CaCu2O8+x

Abstract

We report measurements of the momentum dependence of the superconducting gap in ${\mathrm{Bi}}_2{\mathrm{Sr}}_2\mathrm{Ca}{\mathrm{Cu}}_2{\mathrm{O}}_{8+x}$ with angle-resolved photoemission spectroscopy using a dense sampling of the Brillouin zone in the vicinity of the Fermi surface. In the $Y$ quadrant of the zone, where there are no complications from ghost bands caused by the superlattice, we find a gap function consistent within error bars to the form $cos\left(k_x\right)-cos\left(k_y\right)$ expected for a $d$-wave order parameter. Similar results are found in the $X$ quadrant with the photon polarization chosen to enhance main band emission over that due to ghost bands.