Probing Unconventional Transport Regimes in Delafossite Metals

This thesis describes in-depth studies of the remarkable electronic transport within the ultrahigh conductivity delafossite metals PtCoO_2 and PdCoO_2 using the tool of focused ion beam (FIB) microstucturing. Despite being first synthesised over 50 years ago, important questions remain regarding both the origin of the unusually high conductivity of these compounds and the consequences of their unique properties for unconventional electronic transport, such as that within the ballistic regime. The thesis explores both these areas.

High-energy electron irradiation is used to examine the effects of deliberately introducing point defects into PdCoO_2 and PtCoO_2, demonstrating that the extremely low resistivity of these materials stems from an extreme purity as high as 1 defect in 120,000 atoms, rather than a novel scattering suppression mechanism. In addition, studies of the electronic transport in micron-scale squares of these metals show that their broadly hexagonal Fermi surfaces lead not only to long range ballistic behaviour but novel ballistic regime phenomena which cannot be observed in materials with a higher-symmetry Fermi surface.

Nominated as an outstanding PhD thesis by Max Planck Institute of Chemical Physics of Solids, Dresden Introduces novel focused ion beam microstructuring methods for high-conductivity materials and cryogenic irradiation Explores the impact of a lower-symmetry Fermi surface on the symmetries and scale of ballistic transport phenomena

Auteur

Philippa McGuinness received an MPhys in Physics from the University of Manchester, UK in 2016 and completed her PhD in 2021 as a member of the Scottish Doctoral Training Centre in Condensed Matter Physics, working between the Max Planck Institute for the Chemical Physics of Solids in Dresden, Germany and the University of St Andrews in Scotland, studying the electrical transport of two highly conductive delafossite metals using the tool of focused ion beam microstructuring.

Contenu
Introduction.- The Ultrapure Delafossite Metals PdCoO2 and PtCoO2.- Creation and Measurement of Microstructures of Ultrapure Materials.- High Energy Electron Irradiation of Delafossite Metals.- Ballistic Transport in Square Junctions of Delafossite Metals.- Conclusions and outlook.