Angle resolved photoemission spectroscopy of delafossite metals
Abstract
This thesis describes the results of angle resolved photoemission spectroscopy (ARPES)
experiments on delafossite oxide metals, and theoretical work explaining the observations.
The main results of the thesis are reported in three chapters, each of which
is dedicated to a different physical observation, as I describe below.
The delafossite metals exhibit extraordinarily high conductivity, motivating a
study of bulk electronic structure. I report measurements of the bulk electronic
structure of the non-magnetic delafossites PdCoO₂ and PtCoO₂. In each, a single
fast band crosses the Fermi level, resulting in a highly two-dimensional Fermi surface
of nearly hexagonal cross-section. The detailed differences between the materials are
described, and so are the possible many-body renormalisations.
Extension of the measurements to the electronic structure of the antiferromagnetic
delafossite metal PdCrO₂ reveals a signal which I realised cannot be explained in
terms of standard pictures of electron behaviour in a periodic potential. Using a
combination of experiment and theory, partly in collaboration with external groups,
we were able to identify its origin as the Kondo-like coupling of itinerant Pd - and
localised Cr - electrons. In doing so we are able to show that that ARPES can be
sensitive to spin-spin correlations.
Furthermore, I report measurements and analysis of the surface states arising
from the transition metal terminated surfaces of PtCoO₂, PdCoO₂ and PdRhO₂.
The states support a large Rashba-like spin-splitting, the energy scale of which
is comparable to the atomic spin-orbit coupling of the relevant transition metal
ion. I show how this arises as a consequence of the large energy scale of inversion
symmetry breaking at the surface, and that this is in turn a consequence of the
unusual structure of the transition metal oxide layer.
Type
Thesis, PhD Doctor of Philosophy
Collections
Description of related resources
https://doi.org/10.17630/0b976971-8f36-48d1-a662-e13f4629400dAngle resolved photoemission spectroscopy of delafossite metals (thesis data) Sunko, V., University of St Andrews. DOI: https://doi.org/10.17630/0b976971-8f36-48d1-a662-e13f4629400d
Related resources
https://doi.org/10.17630/0b976971-8f36-48d1-a662-e13f4629400dItems in the St Andrews Research Repository are protected by copyright, with all rights reserved, unless otherwise indicated.