Fate of charge order in overdoped La-based cuprates

TL;DR

This study investigates how stripe charge order in overdoped cuprates evolves, revealing a transition from long-range order to short-range correlations at a critical doping level, using high-resolution RIXS techniques.

Contribution

It provides the first systematic RIXS analysis of charge correlations across doping levels in LSCO and LESCO, identifying a critical doping where stripe order disappears.

Findings

Long-range stripe order is replaced by short-range correlations at x=0.15.

Stripe order vanishes at a quantum critical point near optimal doping.

Short-range correlations are linked to electron-phonon coupling effects.

Abstract

In high-temperature cuprate superconductors, stripe order refers broadly to a coupled spin and charge modulation with a commensuration of eight and four lattice units, respectively. How this stripe order evolves across optimal doping remains a controversial question. Here we present a systematic resonant inelastic x-ray scattering (RIXS) study of weak charge correlations in La2-xSrxCuO4 (LSCO) and La1.8-xEu0.2SrxCuO4 (LESCO). Ultra high energy resolution experiments demonstrate the importance of the separation of inelastic and elastic scattering processes. Upon increasing doping x, the long-range temperature dependent stripe order is found to be replaced by short-range temperature independent correlations at a critical point xc = 0.15 distinct from the pseudogap critical doping. We argue that the doping and temperature independent short-range correlations originate from unresolved electron-phonon coupling that broadly peaks at the stripe ordering vector. In LSCO, long-range static stripe order vanishes in a quantum critical point around optimal doping.