Banca de DEFESA: RODRIGO HENRIQUE DE BRAGANÇA

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
DISCENTE: RODRIGO HENRIQUE DE BRAGANÇA
DATA : 10/03/2025
HORA: 14:00
LOCAL: Através de Videoconferência
TÍTULO:

Supercondutividade Nano e Mesoscópica: Efeito de Bordas Dependentes do Material e o Impacto de Desordem Correlacionada na Temperatura de Superfície e o Aprimoramento do Efeito de Catraca de Vórtices em Nano Tubos e Nano Pétalas Supercondutoras

PALAVRAS-CHAVES:

Surface Superconductivity, BdG equations, tight-binding, Lang-Kohn Potential,
Time-Dependent Ginzburg-Landau, Link-Variables, Open Nanotubes, Vortex Ratchet Effect.

PÁGINAS: 136
RESUMO:

The goal of this work is push the understanding of superconductivity in two different areas:
nanoscopic and mesoscopic, by using numerical experiments. We consider the phenomena of
surface superconductivity with realistic confining potential and how the vortex diode effect
can be enhanced by extending structures into the third dimension.
In the first part of this thesis we have reviewed the basic phenomena of superconductivity
such as the Meissner effect and the phenomenological theories of Ginzburg-Landau. We
estabilish the important concepts of penetration depth and coherence length. Then the microscopical
description of superconductivity is discussed by considering the formation of Cooper
pairs and the Bardeen-Cooper-Schriffer theory. Bu using the Bogoliubov-de Gennes equations
in the tight binding model we are able to investigate the surface enchancement of the critical
temperature. However, the incorporation of a realistic confining potential has not been done
to study the surface superconducting efect. We consider briefly the density functional theory
and discuss the different incremental theories that contributed to the current understanding of
electronic behavior near a surface/interface. We show a numerical method to obtain the Lang-
Kohn potential self-consistently and a second numerical procedure to solve the Bogoliubov-de
Gennes equations in the tight-binding formalism to study the roboustness of the surface superconducting
effect against the surface potential. We have found that the enhancenment of
the surface critical temperature strongly depends on the bulk paramenters such as the electron
density paramenter and the Fermi energy. This means that superconducting properties of a
surface can be controlled by the surface potential properties which gives a way to control the
superconducting state at the surface.
Extending of nanostructures into the third dimension has become a major research avenue
in condensed-matter physics, because of geometry- and topology-induced phenomena. We
consider 2 nanostructures: nanopetal and nanotubes and analyse how they can be useful to
technological applications. To study said structures we consider an extension of the Ginzburg-
Landau theory to incorporate time variation of the order paramenter. We iconsider the linkvariable
method to numerical solve these equations. We then apply this formalism to study how
the nanopetal and nanotube can enchance the vortex diode effect and what kind of structure
is best in relation to fabrication and cost.

MEMBROS DA BANCA:
Externo à Instituição - ANDREY CHAVES - UFC
Externo à Instituição - CARLOS ALBERTO BRAYNER DE OLIVEIRA LIRA - UFPE
Presidente - 1130930 - JOSE ALBINO OLIVEIRA DE AGUIAR
Externo à Instituição - JOSE SOARES DE ANDRADE JUNIOR - UFC
Interno - 2378411 - RENE RODRIGUES MONTENEGRO FILHO