Incommensurate lattice distortion in the high temperature tetragonal phase of La$_{2-x}$(Sr,Ba)$_{x}$CuO$_{4}$

TL;DR

This study reveals incommensurate lattice distortions in the high-temperature tetragonal phase of La$_{2-x}$(Sr,Ba)$_{x}$CuO$_{4}$, showing universal incommensurate lattice instability linked to superconductivity through neutron diffraction analysis.

Contribution

It demonstrates the presence of incommensurate diffuse scattering in the HTT phase of La$_{2-x}$(Sr,Ba)$_{x}$CuO$_{4}$ and characterizes its temperature dependence, revealing a universal lattice instability in hole-doped cuprates.

Findings

Incommensurate diffuse peaks appear in the HTT phase for superconducting samples.

The incommensurability scales with temperature as T/T_s.

ICD peaks are absent in non-superconducting x=0.05 sample.

Abstract

We report incommensurate diffuse (ICD) scattering appearing in the high-temperature-tetragonal (HTT) phase of La$_{2-x}$(Sr,Ba)$_{x}$CuO$_{4}$ with $0.07 \leq x \leq 0.20$ observed by the neutron diffraction technique. For all compositions, a sharp superlattice peak of the low-temperature-orthorhombic (LTO) structure is replaced by a pair of ICD peaks with the modulation vector parallel to the CuO$_6$ octahedral tilting direction, that is, the diagonal Cu-Cu direction of the CuO$_2$ plane, above the LTO-HTT transition temperature $T_s$. The temperature dependences of the incommensurability $\delta$ for all samples scale approximately as $T/T_s$, while those of the integrated intensity of the ICD peaks scale as $(T-T_s)^{-1}$. These observations together with absence of ICD peaks in the non-superconducting $x=0.05$ sample evince a universal incommensurate lattice instability of hole-doped 214 cuprates in the superconducting regime.