Charge modulations in La2CuO4-based cuprates

Electron microscopy experiments reveal that in a Cu-rich polycrystalline La2CuO4.003, grains may phase separate into hole-rich and hole-poor grains at room temperature and in a hole-rich crystalline grain, holes are distributed inhomogeneously over a distance that is smaller than 500 nm. In a hole-rich grain it is shown that hole modulation superlattice reflections may be induced by electron beam, and the size of the modulation domain is estimated to be around 150 nm. The observed modulation superlattice reflections are shown to result from hole localization around a set of parallel modulation planes that are inclined to the CuO2 planes. When intersecting with a CuO2 plane, holes lying on and close to the set of modulation planes form a two-dimensional hole stripe pattern on the CuO2 plane. It is suggested that the observed static hole stripes result from the pinning of fluctuating stripes by electron-beam induced effects. Our results indicate that holes associated with the same modulation plane but different CuO2 planes are strongly correlated and interlayer hole interaction is not in general negligible