Abstract :
[en] The present thesis focuses on the physics of various solid-state systems sharing the
common feature of involving 3d electrons with a low-dimensional aspect for transport,
and studied using Density Functional Theory. Exploiting an original hybrid functional
approach for the exchange-correlation energy, with improved accuracy compared to
local/semi-local functionals, we present the seminal two-dimensional electron system
(2DES) at the (001) interface of band insulators SrTiO3 and LaAlO3 , and review two
of the most popular hypotheses about its origin, namely the electric-field driven Zener
breakdown model and polarity-induced surface oxygen vacancies model. This analysis
is extended to the interface between SrTiO3 and the (Sr1−xLax)(Ti1−xAlx)O3 alloy. We
also study, based on experiments and theoretical modelling, how the composition of the
alloy overlayer affects the charge density of the 2DES. We then address the effect of
structural confinement on the 2DES when the host layer thickness is reduced toward
the very-thin limit, and how such effects are witnessed in angle-resolved photo-emission
spectroscopy experiments. We study the effects of capping the SrTiO 3 /LaAlO 3 het-
erostructures with SrTiO 3 , highlighting how experiments may be interpreted from the
aforementioned electric-field driven models. This work also focuses on the thermoelec-
tric properties of layered oxides, specifically Ca3Co4O9 and SrTiO3 -based superlattices,
discussing the relevance of their layered structure for improving the thermoelectric prop-
erties. Importing the concepts of low-dimensional transport found in SrTiO3 -based sys-
tems to the iron-based Heusler Fe2YZ family, we explore the effect of electron doping,
highlighting magnetic instabilities related to their Fe 3d orbitals, which impact signif-
icantly the thermoelectric properties. Finally, shifting our attention on Fe2TiSn, we
rationalize experimental results provided by collaborators from first-principles, address-
ing the role of native defects and their relevance for tailoring transport.
