Correlation between flux pinning and inhomogeneous electronic distribution of Bi2 Sr2 CaCu2 O8+δ directly probed by scanning tunneling microscopy/spectroscopy

The correlation between the vortex distribution and electronic inhomogeneity in Bi2 Sr2 CaCu2 O8+δ single crystals has been studied by scanning tunneling microscopy/spectroscopy at 4.3 K under 8 T. Vortices have been visualized by mapping the differential tunneling conductance at 12.5 meV, at which quasiparticles form a bound state. We found that vortices tend to form a triangular lattice with a spacing of a0 =1.07 ( 0 B) 1 2 within a short range of ∼ a0, but that the triangular correlation is absent at longer ranges. By comparing the vortex distribution pattern and the spatial map of the gap value, we conclude that the vortices are predominantly trapped in the regions displaying relatively large gaps and rounded gap edges.