Fig. 2

Doping dependence of charge ordering and electronic structures. a–e Various charge orders with increasing doping p in LSCO. The white rhombus, with an acute interior angle of 68°, indicates the formation of distorted Wigner crystal, while the squares mark the unit-cell of √2 × √2 surface reconstruction throughout. Colored spheres, each of which denotes an atom as specified in Fig. 1a, are overlaid on the surfaces to exemplify the 4a₀-period commensurate stripes in c and √2 × √2 reconstruction in d. Tunneling conditions: a V = −4.0 V, I = 40 pA; b V = −3.6 V, I = 20 pA; c V = −3.0 V, I = 60 pA; d V = −2.4 V, I = 15 pA; e V = −2.0 V, I = 20 pA. The scale bar widths are 2 nm in a, 5 nm in b, and 1 nm in c–e. f Spatially averaged dI/dV spectra on various charge-ordered phases as indicated. The setpoints are kept to the starting voltages for every voltage ramp from the negative side, while the current I is fixed at 200 pA except for the √2 × √2 reconstructed surface (I = 100 pA)