Publication: PHYSICAL PROPERTIES OF NANOMATERIALS: WITH APPLICATIONS TO PENTAGONAL SYSTEMS
Date
2019
Authors
BRAVO CASTILLO, SERGIO JAVIER
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Abstract
In this thesis we theoretically study a set of novel systems, known as pentagonal
materials. Physical properties of interest such as electronic structure,
optical response, electronic transport properties and the existence of topological
phases are analyzed. We have employed well-established techniques as well
as innovative approaches in order to get a detailed picture of all the mentioned
features. The structure of the work is described next.
In Part I we present the theoretical concepts that are used throughout the
entire thesis. Such topics are symmetry basics, with group theory generalities,
first-principles methods, the tight-binding approximation, optical response in
the tight-binding approximation, electronic transport in the ballistic regime
and topological properties of materials. The exposition is brief, highlighting
only the needed concepts for the subsequent parts.
Part II concerns with the electronic, optical and transport properties of
penta-graphene (PG) and its nanostructures. We show how penta-graphene
responds to an electromagnetic field perturbation analyzed within the tightbinding
approach. We also compute features of the electronic structure of
penta-graphene and its nanostructures by means of first-principles and tightbinding
methods. We obtain good accordance between these two approaches
in electronic and optical response. Also, a promising thermoelectric transport
performance is found for a particular device configuration.
Part III includes the theoretical study and numerical calculation of symmetryenforced
and topological properties of pentagonal materials. We use several
examples of PG-derived systems by doping or adsorption. This allows us to
design different phases such as trivial metallic phases with nodal lines, Dirac
nodes in presence of spin-orbit coupling and time-reversal symmetry breaking
phases with a non-trivial Chern insulator character. Identification of additional
phases like Weyl nodes, weak and crystalline topological phases is also feasible.
Topological properties were studied by the calculation of topological invariants
with the Wannier charge center evolution method and also by a recent
theoretical framework called topological quantum chemistry.
Considering all the results obtained in this work, we can assert that pentagonal
materials represent a promising family of low dimensional systems with
many interesting physical properties that deserve to be studied in more detail
in upcoming years.
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Keywords
TRANSPORTE ELECTRÓNICO , MODELOS DE ENLACE FUERTE , TOPOLOGÍA