Impact of electron correlations on the $\mathbf{k}$-resolved electronic structure of PdCrO$_{2}$ revealed by Compton scattering

TL;DR

This study investigates how electron correlations influence the electronic structure of PdCrO₂, using Compton scattering and advanced theoretical models, revealing limitations of current methods in capturing all spectral features.

Contribution

It demonstrates that DFT+DMFT accurately predicts the Fermi surface but fails to reproduce certain spectral weight features observed in Compton data, indicating the need for more comprehensive models.

Findings

DFT+DMFT agrees with ARPES on Fermi surface shape

Discrepancy in spectral weight features in Compton data

Electron interactions beyond DFT+DMFT are necessary

Abstract

Delafossite PdCrO$_2$ is an intriguing material which displays nearly-free electron and Mott insulating behaviour in different layers. Both angle-resolved photoemission spectroscopy (ARPES) and Compton scattering measurements have established a hexagonal Fermi surface in the material's paramagnetic phase. However, the Compton experiment detected an additional structure in the projected occupancy which was originally interpreted as an additional Fermi surface feature not seen by ARPES. Here, we revisit this interpretation of the Compton data. State-of-the-art density functional theory (DFT) with dynamical mean field theory (DMFT), the so-called DFT+DMFT method, predicts the Mott insulating state along with a single hexagonal Fermi surface in excellent agreement with ARPES and Compton. However, DFT+DMFT fails to predict the intensity of the additional spectral weight feature observed in the Compton data. We infer that this discrepancy may arise from the DFT+DMFT not being able to correctly predict certain features in the shape and dispersion of the unoccupied quasiparticle band near the Fermi level. Therefore, a theoretical description beyond our DFT+DMFT model is needed to incorporate vital electron interactions, such as inter-layer electron coupling interactions which for PdCrO$_2$ gives rise to the Kondo-like so-called intertwined excitation.