Bulk States in PtCoO$_{2}$ and PdCoO$_{2}$

Abstract

Understanding the exceptionally high conductivity of delafossite oxides, as well as the unconventional transport properties it causes, requires a good knowledge of their electronic structure. As discussed in Sect. 1.1.3, prior to the work presented here both quantum oscillation and photoemission measurements were performed on the Pd based delafossites, $\text {PdCoO}_2$ and $\text {PdCrO}_2$ [1,2,3,4,5,6], while the available $\text {PtCoO}_2$ crystals were too small to make such experiments feasible. In Sects. 4.1 and 4.2 of this chapter I report the first measurements of the electronic structure of $\text {PtCoO}_2$, as well as new ARPES measurements on $\text {PdCoO}_2$ which will be used to compare the two compounds. As discussed in Sect. 2.6.5, the majority of the photoemission measurements on delafossites reveal signatures of both bulk and surface states. However, one of our cleaves from each of $\text {PtCoO}_2$ and $\text {PdCoO}_2$ showed no signs of surface states arising from either of the surface terminations. This greatly simplifies the analysis and interpretation of the bulk electronic structure, so I will concentrate on the results obtained from these two samples. The effective masses and electron counts extracted from the photoemission data will also be compared to density functional theory calculations and bulk-sensitive quantum oscillation measurements.