Collective spin excitations in trilayer nickelate La$_4$Ni$_3$O$_{10}$

TL;DR

This study investigates collective spin excitations in trilayer nickelate La$_4$Ni$_3$O$_{10}$ using RIXS, revealing weaker correlations and differences from bilayer nickelates, which are relevant for understanding superconductivity.

Contribution

First RIXS study of La$_4$Ni$_3$O$_{10}$ revealing weaker spin spectral weight and electronic correlations compared to bilayer nickelates.

Findings

Spin excitations have a bandwidth of about 60 meV.

Spectral weight of spin excitations is substantially suppressed.

Electronic correlations are weaker in trilayer La$_4$Ni$_3$O$_{10}$.

Abstract

Ruddlesden-Popper (RP) nickelates have recently emerged as a new family of high-temperature superconductors. In bilayer RP nickelates, magnetic excitations with large exchange couplings have been observed, supporting a spin-mediated pairing mechanism. Whether comparable spin correlations persist in trilayer nickelates, however, remains unknown. Here, we present a Ni $L$-edge resonant inelastic X-ray scattering (RIXS) study of La$_4$Ni$_3$O$_{10}$ single crystals. While the orbital excitations remain similar to those of La$_3$Ni$_2$O$_{7}$, the collective spin excitations in La$_4$Ni$_3$O$_{10}$ exhibit a comparable bandwidth of about $60$ meV but substantially suppressed spectral weight, implying a weaker electronic correlation in the trilayer compounds. Our results underscore the three-dimensional and multi-orbital electronic character in La$_4$Ni$_3$O$_{10}$, highlighting important differences from the bilayer nickelates. These findings provide crucial insights into the evolution of magnetism across the RP nickelate family and its connection to superconductivity.