Hidden Quasiparticles and Incoherent Photoemission Spectra in Na2IrO3

TL;DR

This paper investigates the electronic spectral properties of Na$_2$IrO$_3$ using two theoretical models, revealing universal incoherent spectral features and suppressed quasiparticles consistent with experimental photoemission data.

Contribution

It demonstrates that incoherent spectral weight dominates in Na$_2$IrO$_3$, providing a theoretical explanation for suppressed quasiparticles and pseudogap-like features observed experimentally.

Findings

Spectral functions show large incoherent weight at high energy.

Quasiparticles at low energy are strongly suppressed.

Models produce spectra similar to experimental ARPES data.

Abstract

We study two Heisenberg-Kitaev t-J-like models on a honeycomb lattice, focusing on the zigzag magnetic phase of Na$_2$IrO$_3$, and investigate hole motion by exact diagonalization and variational methods. The spectral functions are quite distinct from those of cuprates and are dominated by large incoherent spectral weight at high energy, almost independent of the microscopic parameters --- a universal and generic feature for zigzag magnetic correlations. We explain why quasiparticles at low energy are strongly suppressed in the photoemission spectra and determine an analog of a pseudogap. We point out that the qualitative features of the predominantly incoherent spectra obtained within the two different models for the zigzag phase are similar, and they have remarkable similarity to recently reported angular resolved photoemission spectra for Na$_2$IrO$_3$.