Suppression of ballistic effects in the ultra-pure delafossite PtCoO₂via high-energy electron irradiation

PtCoO₂ is a layered oxide delafossite material which has a hexagonal, single-band Fermi surface. This ultrapure metal is extremely conductive, with a low-temperature mean free path of up to 5 μm [1]. Due to these properties, novel low-temperature ballistic effects have been demonstrated in the magnetoresistance of micron-scale ultrapure delafossite devices [2]. To determine the sensitivity of the ballistic behavior to disorder, we have used 2.5 MeV electron irradiation to introduce point-defect impurities into PtCoO₂ microstructures. This reduces the mean free path and therefore suppresses the ballistic phenomena. Surprisingly, these effects remain, in a weaker form, at an impurity level significantly higher than would be expected from the usual limits of the ballistic regime.

[1] Kushwaha, P. et al. Science Advances 1, e1500692–e1500692 (2015)
[2] Bachmann, M. et al. arXiv:1902.03769