4a×4aelectronic charge order enhanced in the inhomogeneous pseudogap state ofBi2Sr2CaCu2O8+δ

Scanning tunneling microscopy and spectroscopy are used to examine the $4a\ifmmode\times\else\texttimes\fi{}4a$ electronic charge order (CO) and the spatial dependence of energy gap in the pseudogap (PG) state above ${T}_{c}$ on ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Ca}{\mathrm{Cu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$. We report the first observation on energy gap inhomogeneity in the PG state, together with the result that the static CO develops markedly in the inhomogeneous PG state, although it is very weak in the homogeneous PG state. This static CO, which is considered to be stabilized by the pinning of the dynamically fluctuating CO, can coexist with the superconductivity below ${T}_{c}$.