On Nematicity and Charge Order in Superoxygenated La$_{2-x}$Sr$_x$CuO$_{4+y}$

TL;DR

This study investigates nematicity and charge order in superoxygenated La$_{2-x}$Sr$_x$CuO$_{4+y}$, revealing that resonant (001) reflections are not universal among cuprates and depend on specific structural and electronic conditions.

Contribution

It provides the first direct comparison of resonant scattering features in different La$_{2-x}$Sr$_x$CuO$_{4+y}$ samples, challenging the universality of nematic order signatures.

Findings

Charge order observed near 0.125 hole concentration in La$_2$CuO$_{4+y}$.

Resonant (001) peak absent in La$_{2}$CuO$_{4+y}$ with stripe order.

Resonant (001) peak present in La$_{1.94}$Sr$_{0.06}$CuO$_{4+y}$ with LTT tilting.

Abstract

A nematic order in stripe-ordered cuprates was recently identified with (001) reflection at resonant energies associated with the in-plane states. However, whether this resonant reflection is ubiquitous among all 214 cuprates is still unknown. Here we report a Resonant soft X-ray Scattering (RXS) measurement on two La$_{2-x}$Sr$_x$CuO$_{4+y}$ crystals. Charge order was found in La$_2$CuO$_{4+y}$ with a total hole concentration near 0.125/Cu but no measurable (001) peak at any resonance, while in a La$_{1.94}$Sr$_{0.06}$CuO$_{4+y}$ sample near 0.16/Cu a (001) peak resonant was identified to be consistent with the presence of LTT tilting. The lack of such a (001) peak in a compound with stripe-like charge order raises questions about nematicity and the origin of the scattering feature.