Coulomb correlations intertwined with spin and orbital excitations in LaCoO$_3$

TL;DR

This study investigates how Coulomb interactions, spin, and orbital excitations evolve with temperature in LaCoO₃, revealing an orbital-selective screening effect linked to a Mott transition during the spin-state crossover.

Contribution

It provides new insights into the interplay between Coulomb correlations and spin/orbital excitations in LaCoO₃ using temperature-dependent RIXS and charge-transfer calculations.

Findings

Orbital-selective screening of Coulomb interactions.

Identification of a Mott-type insulator-to-metal transition.

Correlation between spin-state crossover and Coulomb energy changes.

Abstract

We carried out temperature-dependent (20 - 550 K) measurements of resonant inelastic X-ray scattering on LaCoO$_3$ to investigate the evolution of its electronic structure across the spin-state crossover. In combination with charge-transfer multiplet calculations, we accurately quantized the renormalized crystal-field excitation energies and spin-state populations. We show that the screening of the on-site Coulomb interaction of 3d electrons is orbital selective and coupled to the spin-state crossover in LaCoO$_3$. The results establish that the gradual spin-state crossover is associated with a relative change of Coulomb energy versus bandwidth, leading to a Mott-type insulator-to-metal transition.