63Cu NQR evidence for spatial variation of hole concentration in La2-xSrxCuO4 -: art. no. 047602

We report experimental evidence for the spatial variation of hole concentration x(hole) in the high T-c superconductor La2-xSrxCuO4 (0.04 less than or equal to x less than or equal to 0.16) via Cu-63 NQR using Cu-63 isotope enriched samples. We demonstrate that the extent of the spatial variation of the local hole concentration Deltax(hole) is reflected on (63)l /T-1 and deduce the temperature dependence. Deltax(hole) increases below 500-600 K, and reaches values as large as Deltax(hole)/x similar to 0.5 below similar to150 K. We estimate the length scale of the spatial variation in x(hole) to be R-hole greater than or similar to 3 nm from an analysis of the NQR spectrum.