Inhomogeneous CuO_{6} Tilt Distribution and Charge/Spin Correlations in La_{2-x-y}Nd_{y}Sr_{x}CuO$_{4} around commensurate hole concentration

TL;DR

This study investigates the disorder in CuO6 octahedral tilts and their relation to charge and spin correlations in La-based cuprates near 1/8 doping, revealing persistent tilt disorder and weak charge/spin modulations.

Contribution

It provides detailed Raman scattering analysis showing inhomogeneous tilt patterns and their coupling to cation layer disorder across different doping levels.

Findings

Persistent tilt disorder down to 10 K

Coupling of tilt disorder to cation layer bond disorder

Weak charge/spin modulations not detectable via Raman signatures

Abstract

Phononic and magnetic Raman scattering are studied in La$_{2-x-y}$Nd$_{y}$Sr$_{x}$CuO$_{4}$ with three doping concentrations: x ~ 1/8, y = 0; x ~ 1/8, y = 0.4; and x = 0.01, y = 0. We observe strong disorder in the tilt pattern of the CuO_{6} octahedra in both the orthorhombic and tetragonal phases which persist down to 10 K and are coupled to bond disorder in the cation layers around 1/8 doping independent of Nd concentration. The weak magnitude of existing charge/spin modulations in the Nd doped structure does not allow us to detect the specific Raman signatures on lattice dynamics or two-magnon scattering around 2200 cm-1.