Banca de DEFESA: RICARDO DE LIMA SILVEIRA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RICARDO DE LIMA SILVEIRA
DATE: 21/03/2022
TIME: 14:00
LOCAL: https://meet.google.com/jiu-xtnw-vdq
TITLE:

Confinement induced variation of the power-law decay of the order parameter in the low-temperature proximity effect

KEY WORDS:

Proximity effect; quantum confinement; Bogoliubov-de Gennes equations.

PAGES: 82
BIG AREA: Ciências Exatas e da Terra
AREA: Física
SUMMARY:

This thesis aims to investigate how the proximity effect is affected by the quantum confinement
of charge carriers. This phenomenon, which consists essentially in the diffusion of superconducting
correlations into a non-superconducting metal, has been widely studied over several
decades, but not so much in the regime in which the quantum confinement of electrons affects
the properties of the system. We aim, more specifically, to determine the functional form for
the decay of the pair amplitude in cylindrical nanowires of normal metals in the ballistic limit
and at zero temperature. It is known that quantum confinement leads to fluctuations in the
values of superconducting quantities, such as the energy gap. This can be expected to affect
how strongly the wave function of an electron pair decays in the normal metal. To investigate
this problem, we solve the Bogoliubov-de Gennes equations self-consistently in nanowires with
different diameters. Based on the literature on the proximity effect at low temperatures in
clean metals, we model the behavior of the superconducting correlations in the normal metal
by an inverse power law decay, with exponent 𝛼. The value of this parameter is extracted from
the data obtained numerically for each diameter. We found that this parameter follows an
oscillatory pattern whose peaks and valleys correspond to those observed in the energy gap.

BANKING MEMBERS:
Externa à Instituição - NATALIA PUGACH
Externo à Instituição - ANTONIO RODRIGUES DE C.ROMAGUERA - UFRPE
Interno - 1130930 - JOSE ALBINO OLIVEIRA DE AGUIAR
Presidente - 3102524 - MIHAIL CROITORU