Exchange interaction at the Pd surface electronic bands in delafossite oxides PdCrO₂and PdCoO₂

Two-dimensional (2D) metals hold significant physical interest and promise for future technologies due to their unique properties, which arise from spatial confinement and enhanced electronic fluctuations. Although the properties of a 2D electron gas/liquid are generally well understood, how these properties in one material are influenced by electronic correlations in a neighbouring material remains an underexplored question. Using quasiparticle interference measurements in scanning tunnelling microscopy, we investigated how the quasiparticle properties of the Pd-terminated surfaces of delafossite oxides PdCrO₂and PdCoO₂, originating from the same mechanism, are differently affected by the antiferromagnetic Mott-insulating CrO₂layers in PdCrO₂and the non-magnetic band-insulating CoO₂layers in PdCoO₂below. By comparing the experimental results with tight binding calculations based on a minimal model, we gain a qualitative understanding of the distinct exchange interactions present in these two systems.