Landau theory of the density wave transition in trilayer Ruddlesden-Popper nickelates

TL;DR

This paper develops a Landau theory to analyze the incommensurate density wave transition in trilayer Ruddlesden-Popper nickelates, explaining how charge and spin orders intertwine and how transition temperatures vary with external factors.

Contribution

It introduces a Landau theoretical framework specifically for the density wave transition in trilayer Ruddlesden-Popper nickelates, linking experimental observations with phase transition theory.

Findings

Transition is spin-driven with intertwined charge and spin order.

Transition temperature varies with rare earth size, pressure, and isotope substitution.

The transition is near a first-order phase boundary in the Landau phase diagram.

Abstract

This paper presents a Landau treatment of the incommensurate density wave transition observed in trilayer Ruddlesden-Popper nickelates and uses this to address the nature of the transition. The data are consistent with a spin driven transition with the distinct intertwining of charge and spin order due to being in or proximate to the first order transition region of the Landau phase diagram. From this approach, one also obtains an understanding of the variation of the transition temperature with rare earth size, pressure, and oxygen isotope substitution.