Size restricted magnetotransport in the non-magnetic delafossite metals PdCoO₂ and PtCoO₂

Ultra-pure delafossite metals can present bulk mean free paths as long as tens of microns, long enough such that the momentum conservation of the electron fluid might play a role in electrical transport [1]. As the signatures of this are most prominent in the mesoscopic limit, we use focussed ion beam (FIB) techniques to thin bulk samples down to widths as small as submicron, much smaller than the bulk mean free path. In this talk I will present magnetotransport measurements in these highly-conducting delafossites, specifically PdCoO₂ and PdCoO₂, at the mesoscopic limit. Magnetic field introduces a variable length-scale, the cyclotron radius, to the system which can be used to tune through different transport regimes. I will discuss the ballistic and hydrodynamic signatures in the transport that in principle become accessible through magnetic field tuning in such mesoscopic samples.

[1] Moll, P. J. W., Kushwaha, P., Nandi, N., Schmidt, B. & Mackenzie, A. P. Evidence for hydrodynamic electron flow in PdCoO₂. Science. 351, 1061–1064 (2016).