Electron transport on the hexagonal Fermi surface of PdCoO2

Monday, June 3, 2019 - 11:00am - 12:00pm
Lind 409
Maja Bachmann (Max-Planck-Gesellschaft)
Early experiments in search for hydrodynamic behavior in electron fluids were carried out in ultra-clean semiconductor heterostructures, in which the charge carriers are well described by small, circular Fermi surfaces. In contrast, the electron system in the ultra-pure delafossite metal PdCoO2 is described by a nearly perfect hexagonal Fermi surface, leading to three preferred directions of ballistic electron motion.

We set out to explore how this peculiar electronic structure manifests itself in the ballistic transport behavior of PdCoO2 at 2K, by investigating the transverse magnetic focusing effect as well as the magneto-resistance through narrow channels. This is particularly relevant to establish a complete picture of the exotic ballistic motion in PdCoO2, on top of which strong momentum-conserving scattering processes have been argued to lead to hydrodynamic transport.

In this talk, I will present experimental data and ballistic simulations which demonstrate our understanding of hexagonal cyclotron motion in PdCoO2. Key to these experiments is the precise micro-machining of single crystals into transport devices using a focused ion beam (FIB). It offers a high level of control over the crystal axes (0.5 deg) and allows for feature sizes down to 30nm (much smaller than the mean free path).