Controlled introduction of defects to delafossite metals by electron irradiation*

The delafossite metals PdCoO₂ and PtCoO₂ are among the highest conductivity materials known. At room temperature the mean free path is at least twice as long as those of silver or copper, and at low temperature mean free paths of tens of microns are observed in as-grown single crystals, enabling searches for unusual regimes of ballistic and hydrodynamic electrical transport. In parallel with that class of experiments, we wish to understand the microscopic mechanisms for the existence of these extraordinary mean free paths. Somewhat paradoxically, one route to obtaining more insight is to deliberately introduce point defects and study their effect on the electrical transport properties. We report on a systematic study in which both bulk single crystals and focused ion beam sculpted mesostructures are irradiated with 0.8 - 2.5 MeV electrons and their transport properties studied both in- and ex-situ.