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

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.