Relationship between charge stripe order and structural phase transitions in La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$

TL;DR

This study investigates how charge stripe order relates to structural phase transitions in La-based cuprates, revealing that charge order behavior varies with composition and temperature, and correlates with structural changes.

Contribution

It provides a detailed analysis of charge stripe order and its relationship with structural phase transitions across different compositions in La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$, highlighting the precursor phenomena and transition dynamics.

Findings

Charge order disappears at $T_{d2}$ for $x=0.05$.

Short-range charge correlations persist above $T_{d2}$ for $x=0.075$ and 0.09.

Transition processes into charge stripe order are strongly linked to structural phase changes.

Abstract

The nature of charge stripe order and its relationship with structural phase transitions were studied using synchrotron X-ray diffraction in La$_{1.875}$Ba$_{0.125-x}$Sr$_{x}$CuO$_{4}$ ($0.05\leq x\leq 0.10$). For $x=0.05$, as temperature increased, incommensurate superlattice peaks associated with the charge order disappeared just at the structural phase transition temperature, $T_{\rm d2}$. However, for $x=0.075$ and 0.09, the superlattice peaks still existed as a short range correlation even above $T_{\rm d2}$, indicating a precursor of charge ordering. Furthermore, temperature dependences of the superlattice peak intensity, correlation length, and incommensurability for $x=0.05$ are different from those for $x=0.075$ and 0.09. These results suggest that the transition process into the charge stripe order strongly correlates with the order of the structural phase transitions. A quantitative comparison of the structure factor associated with the charge order have been also made for all the samples.