High-Temperature Charge-Stripe Correlations in La$_{1.675}$Eu$_{0.2}$Sr$_{0.125}$CuO$_4$

TL;DR

This study uses resonant inelastic x-ray scattering to reveal that charge-stripe correlations in La$_{1.675}$Eu$_{0.2}$Sr$_{0.125}$CuO$_4$ occur before structural and pseudogap phases, showing temperature-independent integrated intensity but decreasing peak amplitude.

Contribution

It demonstrates that charge-stripe correlations in La-based cuprates are present above known phase transitions and provides a unified understanding of charge order across different compounds.

Findings

Charge-stripe correlations precede structural and pseudogap phases.

The scattering peak amplitude decays as T^{-2} with temperature.

Integrated scattering intensity remains roughly constant across compounds.

Abstract

We use resonant inelastic x-ray scattering to investigate charge-stripe correlations in La$_{1.675}$Eu$_{0.2}$Sr$_{0.125}$CuO$_4$. By differentiating elastic from inelastic scattering, it is demonstrated that charge-stripe correlations precede both the structural low-temperature tetragonal phase and the transport-defined pseudogap onset. The scattering peak amplitude from charge stripes decays approximately as $T^{-2}$ towards our detection limit. The in-plane integrated intensity, however, remains roughly temperature independent. Therefore, although the incommensurability shows a remarkably large increase at high temperature, our results are interpreted via a single scattering constituent. In fact, direct comparison to other stripe-ordered compounds (La$_{1.875}$Ba$_{0.125}$CuO$_4$, La$_{1.475}$Nd$_{0.4}$Sr$_{0.125}$CuO$_4$ and La$_{1.875}$Sr$_{0.125}$CuO$_4$) suggests a roughly constant integrated scattering intensity across all these compounds. Our results therefore provide a unifying picture for the charge-stripe ordering in La-based cuprates. As charge correlations in La$_{1.675}$Eu$_{0.2}$Sr$_{0.125}$CuO$_4$ extend beyond the low-temperature tetragonal and pseudogap phase, their emergence heralds a spontaneous symmetry breaking in this compound.