Charge-Stripe Ordering From Local Octahedral Tilts: Underdoped and Superconducting La2-xSrxCuO4 (0 < x < 0.30)

TL;DR

This study investigates local octahedral tilt disorder in La2-xSrxCuO4 using neutron PDF analysis, revealing local tilt variations associated with charge stripe order in underdoped and superconducting samples.

Contribution

It provides evidence of local tilt disorder and mixed tilt directions in La2-xSrxCuO4, linking local structural features to charge stripe phenomena.

Findings

Local tilts are LTO in undoped La2CuO4.

Doped samples show a mixture of LTO and LTT local tilt directions.

PDF data are explained by models with local tilt disorder and charge stripes.

Abstract

The local structure of La2-xSrxCuO4, for 0 < x < 0.30, has been investigated using the atomic pair distribution function (PDF) analysis of neutron powder diffraction data. The local octahedral tilts are studied to look for evidence of [110] symmetry (i.e., LTT-symmetry) tilts locally, even though the average tilts have [010] symmetry (i.e., LTO-symmetry) 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 non-zero doping the PDF data are consistent with the presence of local tilt disorder in the form of a mixture of LTO and LTT local tilt directions and a distribution of local tilt magnitudes. We present topological tilt models 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.