Ballistic effects in squares and crosses of the ultra-pure delafossite PtCoO₂

The delafossite PtCoO₂ is a layered oxide material with a single-band, hexagonal Fermi surface. This metal is extremely conductive, with a room temperature resistivity of 1.8 μOhmcm and a low-temperature mean free path of 5 μm [1]. Using focused ion beam microstructuring, we have created PtCoO₂ square and cross devices which demonstrate strong ballistic behavior when their dimensions are similar to this mesoscopic length scale. These ballistic signals, in a weaker form, persist to structure sizes of at least 50 μm. Novel magnetoresistance effects, not observed in materials with circular Fermi surfaces, are also present within these devices, suggesting an influence of the hexagonal Fermi surface on ballistic transport.

[1] Kushwaha, P. et al. Science Advances 1, e1500692–e1500692 (2015)