Charge Condensation and Lattice Coupling Drives Stripe Formation in Nickelates

TL;DR

This study reveals that charge condensation, strongly coupled to the lattice, is the main driver of stripe formation in nickelates, with charge order showing remarkable stability and domain memory even at elevated temperatures.

Contribution

The paper demonstrates that charge condensation, rather than spin interactions, predominantly drives stripe formation in La2-xSrxNiO4+δ, highlighting the role of lattice coupling.

Findings

Charge stripes are more thermally stable than spin stripes.

Charge order exhibits robust domain memory up to 250 K.

Charge condensation is identified as the key factor in stripe formation.

Abstract

Revealing the predominant driving force behind symmetry breaking in correlated materials is sometimes a formidable task due to the intertwined nature of different degrees of freedom. This is the case for La2-xSrxNiO4+{\delta} in which coupled incommensurate charge and spin stripes form at low temperatures. Here, we use resonant X-ray photon correlation spectroscopy to study the temporal stability and domain memory of the charge and spin stripes in La2-xSrxNiO4+{\delta}. Although spin stripes are more spatially correlated, charge stripes maintain a better temporal stability against temperature change. More intriguingly, charge order shows robust domain memory with thermal cycling up to 250 K, far above the ordering temperature. These results demonstrate the pinning of charge stripes to the lattice and that charge condensation is the predominant factor in the formation of stripe orders in nickelates.