Charge-stripe ordering from local octahedral tilts: Underdoped and superconducting La2-xSrxCuO4 (0 <= x <= 0.30)

The local structure of La2-xSrxCuO4, for 0 less than or equal to x less tha n or equal to 0.30, has been investigated using the atomic pair distributio n function (PDF) analysis of neutron powder-diffraction data. The local oct ahedral tilts are studied to look for evidence of [110] symmetry [i.e., low -temperature tetragonal (LTT) symmetry] tilts locally, even though the aver age tilts have [010] symmetry [i.e., low-temperature orthorhombic (LTO) sym metry] in these compounds. We argue that this observation would suggest the presence of local charge-stripe order. We show that the tilts are locally LTO in the undoped phase, in agreement with the average crystal structure. At nonzero doping the PDF data are consistent with the presence of local ti lt disorder in the form of a mixture of LTO and LTT local tilt directions a nd a distribution of local tilt magnitudes. We present topological tilt mod els which qualitatively explain the origin of tilt disorder in the presence of charge stripes and show that the PDF data are well explained by such a mixture of locally small and large amplitude tilts.