Pressure-Invariant Isotope Effect as Evidence for Electronically Driven Intertwined Order in Pr${}_4$Ni${}_3$O${}_{10}$

Abstract

We report muon-spin rotation measurements of the pressure dependence of the oxygen-isotope (${}^{16}$O/${}^{18}$O) effect on the spin-density wave (SDW) transition in the trilayer Ruddlesden-Popper nickelate Pr${}_4$Ni${}_3$O${}_{10}$. At ambient pressure, the SDW transition shows a finite isotope shift, with ${}^{16}{T}_{\mathrm{SDW}}=158.04(5)$ K and ${}^{18}{T}_{\mathrm{SDW}}=159.81(6)$ K. Under hydrostatic pressure, $T_{\mathrm{SDW}}$ decreases linearly at nearly identical rates for the two isotope compositions, $\mathrm{d}{}^{16}{T}_{\mathrm{SDW}}/\mathrm{d}p=-4.93(5)$ K/GPa and $\mathrm{d}{}^{18}{T}_{\mathrm{SDW}}/\mathrm{d}p=-4.90(7)$ K/GPa, such that the isotope shift remains essentially unchanged under compression. The absence of pressure enhancement of the isotope effect points to a predominantly electronic origin of the SDW transition and is consistent with recent inelastic x-ray scattering results, suggesting a new regime of intertwined order in trilayer RP nickelates, which is stabilized by strong spin interactions.

9 pages, 3 figures