Imaging nanoscale electronic inhomogeneity in the lightly doped Mott insulator Ca2-xNaxCuO2Cl2 -: art. no. 097004

The spatial variation of electronic states was imaged in the lightly doped Mott insulator Ca2-xNaxCuO2Cl2 using scanning tunneling microscopy or spectroscopy. We observed nanoscale domains with a high local density of states within an insulating background. The observed domains have a characteristic length scale of 2 nm (similar to4-5a, a: lattice constant) with preferred orientations along the tetragonal [100] direction. We argue that such spatially inhomogeneous electronic states are inherent to slightly doped Mott insulators and play an important role for the insulator to metal transition.