Directional Anomalous Skin Effect in ReO₃

Rhenium oxide (ReO₃) has the lowest residual resistivity of any metallic oxide and consequently has an extremely long low-temperature mean free path, much like the ultrapure delafossites[1]. Both ReO₃ and the quasi-2D delafossite material palladium cobaltate (PdCoO₂) have Fermi surfaces with facetted shapes. The novel directional anomalous skin effect (ASE) has been seen recently in these materials through broadband microwave spectroscopy experiments, and depends on the relative alignment of surface currents and the Fermi surface facets[2]. Non-local Boltzmann transport models effectively describe the anisotropy of the ASE in PdCoO₂, indicating that transport is somewhere between the ballistic and hydrodynamic regimes[3,4].

The directional ASE observed in ReO₃ is more complex, due to the 3-dimensionality of its electronic structure and multiple Fermi surface sheets. Here we will share microwave spectroscopy results for high-conductivity samples of ReO₃ at low temperatures. These results show that the directional ASE response depends not solely on the alignment of the surface current direction with the crystal structure, but also on the direction of the electromagnetic wavevector in the sample. We interpret these findings using transport models.

[1] J. Falke et al., Phys. Rev. B 103, 115125 (2021)

[2] G. Baker, T. W. Branch et al., Phys. Rev. X, 011018 (2024)

[3] D. Valentinis et al., Phys. Rev. Research 5(1), 013212 (2023)

[4] G. Baker, University of British Columbia, Dissertation (2022)