Interplay of phonons, intertwined density waves, and induced spin density wave in trilayer nickelates Pr4-xLaxNi3O10

TL;DR

This study explores how lattice vibrations influence charge and spin orderings in trilayer nickelates, revealing that phonons are highly sensitive to electronic phase transitions and play a key role in emergent phenomena.

Contribution

It provides detailed Raman scattering analysis of phonon behavior across doping levels and temperature, uncovering the lattice's role in metal-to-metal transitions and intertwined density waves.

Findings

Phonon anomalies correlate with metal-to-metal transition.

Significant phonon softening observed near phase transitions.

Lattice dynamics are crucial in mediating spin and charge order.

Abstract

Lattice degrees of freedom (DoF) play a central role in correlated electron systems, strongly influencing the dynamics of the underlying charge carriers and spin excitations. In nickelates, understanding the role of lattice is essential to unravel the interplay between charge, orbital, and spin degree of freedom in giving rise to various emergent phenomena reported recently. Here, we investigate the phononic DoF in a series of trilayer nickelates, namely Pr4-xLaxNi3O10 (where x = 0, 0.4, 1, 2, 3.6, and 4) using temperature and polarization dependent Raman scattering measurements. Our in-depth analysis of the phonon evolution with temperature and doping, gives interesting insights into the behaviour of these materials. All these systems undergo a metal-to-metal transition (TMMT), characterized by the development of intertwined spin and charge density waves, with the spin density wave preceding the charge density wave. These transitions manifest as pronounced anomalies in phonon self-energy parameters i.e. peak frequency and linewidth in the vicinity of the metal-to-metal transition. Several phonon modes show dramatic change (nearly an order of magnitude for some modes) in their softening rates across the TMMT, highlighting the sensitivity of the lattice dynamics to spin and charge order. These findings emphasize the crucial role of lattice DoF in mediating correlated ground states in layered nickelates.