Time-resolved photoemission and RIXS study of a site-selective Mott insulator

TL;DR

This study investigates how different insulating sublattices in a correlated electron system respond to photoexcitation, revealing sublattice-specific dynamics through time-resolved PES and RIXS measurements, inspired by rare earth nickelates.

Contribution

It introduces a combined PES and RIXS approach to distinguish and analyze the nonequilibrium dynamics of two distinct insulating sublattices in a correlated electron system.

Findings

Charge carriers migrate from B to A sublattice.

In-gap states appear in PES signals on the A sublattice.

RIXS signals reveal local state evolution on both sublattices.

Abstract

Inspired by the physics of rare earth nickelates, we study the photoemission (PES) and resonant inelastic X-ray scattering (RIXS) spectra of a correlated electron system with two types of insulating sublattices. Sublattice A is characterized by a hybridization gap and a low-spin state, while sublattice B features a Mott gap and a local magnetic moment. We show how the coupling of these two qualitatively different insulating states affects the dynamics of photo-induced charge carriers and how the nonequilibrium states manifest themselves in the PES and RIXS signals. In particular, we find that charge carriers created on the B sublattice migrate to the A sublattice, where they contribute to the creation of in-gap states in the PES signal, and to characteristic peaks in the nonequilibrium RIXS spectrum. While the contributions from the two sublattices cannot be easily distinguished in the local photoemission spectrum, the weights of the RIXS signals in the two-dimensional $\omega_\text{in}$-$\omega_\text{out}$ space provide information on the local state evolution on both sublattices.