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

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.