Absolute microwave surface impedance of the delafossites: Simulations of non-ellipsoidal geometries

The delafossite metal PdCoO2, with its nearly hexagonal Fermi surface and exceptionally long, anisotropic electron mean free path, has exhibited an array of exotic DC transport phenomena [1]. Microwave cavity perturbation measurements of hexagonal platelet samples of PdCoO2 will allow the anisotropy of the absolute complex surface impedance to be precisely determined. These measurements of surface impedance will in turn allow for the predictions of non-local transport models to be tested, providing differentiation between the contributions of ballistic and hydrodynamic effects to AC electron dynamics in PdCoO2.
In advance of performing cavity perturbation measurements, we have used simulation to explore the effects of non-ellipsoidal sample geometry and material anisotropy on such experiments. These effects are poorly understood, which necessitates the use of limiting approximations when determining the surface impedance. We present refinements to existing approximation methods which will allow electron dynamics in PdCoO2 to be more accurately extracted from cavity perturbation experiments. Preliminary experimental results will also be presented.
[1] Mackenzie, Rep. Prog. Phys. 80 032501 (2017)