Gap-Inhomogeneity-Induced Electronic States in SuperconductingBi2Sr2CaCu2O8+δ

Abstract

In this Letter, we analyze, using scanning tunneling spectroscopy, the density of electronic states in nearly optimally doped ${\mathrm{Bi}}_2{\mathrm{Sr}}_2{\mathrm{CaCu}}_2{\mathrm{O}}_{8+\delta }$ in zero magnetic field. Focusing on the superconducting gap, we find patches of what appear to be two different phases in a background of some average gap, one with a relatively small gap and sharp large coherence peaks and one characterized by a large gap with broad weak coherence peaks. We compare these spectra with calculations of the local density of states for a simple phenomenological model in which a $2{\xi }_0\times 2{\xi }_0$ patch with an enhanced or suppressed $d$-wave gap amplitude is embedded in a region with a uniform average $d$-wave gap.