Comment on " Low-Lying Quasiparticle States and Hidden Collective Charge Instabilities in Parent Cobaltate Superconductors"

TL;DR

This paper critically examines ARPES data on Na0.8CoO2, challenging previous interpretations of Fermi surface splitting and arguing that the observed spectra cannot be explained by bulk electronic structure models.

Contribution

It provides a critical analysis showing that the prior interpretation of ARPES data for Na0.8CoO2 is invalid and offers new insights into the spectral features.

Findings

Previous interpretation of Fermi surface splitting is not supported

Observed spectra cannot be explained by bulk electronic structure

No valid interpretation of ARPES data in terms of bulk properties

Abstract

Qian et al [1] recently reported angular-resolved photoemission spectroscopy (ARPES) measurements for Na0.8CoO2 that show two concentric Fermi surfaces (FS) split by a delta k_F that varies by a factor of three around the Brillouin zone (BZ). The surfaces occupy 70+/-5% of the full 2D BZ and were interpreted as the bonding and antibonding splitting (BAS) of the a1g bands, with an unspecified effect of magnetic ordering. Below we show that this interpretation is not possible, and, in fact, no valid intepretation of the observed spectra in terms of the bulk electronic structure of Na0.8CoO2 can be found.