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Comportamento multicrítico no modelo de Heisenberg frustrado: transições de fases clássica e quântica
(Universidade Federal de São Carlos, 2011-09-01)
In this work we study the critical behavior of systems described by the Anysotropic- Heisenberg model of spin 1/2 with competitive interactions (J1-J2 Model) on planes, and interplane nearest-neighbor interactions. We ...
Ansatz de Bethe algébrico com fronteiras triangulares
(Universidade Federal de São Carlos, 2014-05-26)
In this work we study vertex models with non-diagonal boundaries, characterized by reection matrices with an upper triangular form. By means of an extension of the algebraic Bethe ansatz, we construct generalized Bethe ...
Efeitos de spin em diodos de tunelamento ressonante tipo-p
(Universidade Federal de São Carlos, 2012-03-27)
In this work, we have investigated the spin effects in p-i-p GaAs/AlAs resonant tunneling diodes under magnetic field parallel to the tunnel current. The spin-dependent tunneling of carriers was studied by analyzing the ...
Simulações de líquidos super-resfriados via dinâmica molecular
(Universidade Federal de São Carlos, 2012-10-15)
This work presents the study of two models of glass-forming liquids using molecular dynamics simulations. The first model aims to analyze the effects on glassy dynamics which allow the enhancement of the glass formability ...
Propriedades de transporte de spins polarizados em heteroestruturas semicondutoras
(Universidade Federal de São Carlos, 2009-06-25)
In this work we used the technique of scattering matrix to calculate the transmissivity of polarized spins in a semiconductor symmetrical double-barrier heterostruture. The dynamics of carriers is described by effective ...
Estudo de primeiros princípios das propriedades eletrônicas de novos materiais derivados do grafeno : as nanofitas e nanofios
(Universidade Federal de São Carlos, 2012-09-05)
In this thesis, we study new materials derived from graphene, like nanowires and nanoribbons, with numerical calculations based on the density functional theory (DFT) and the non-equilibrium Green functions (NEGF). We will ...
Flux avalanches in patterned superconducting thin films: ac susceptibility, morphology and related studies
(Universidade Federal de São Carlos, 2013-04-12)
Avalanches are sudden dramatic phenomena that occur in nature. The technique of magneto-optical imaging (MOI) has allowed us to observe abrupt flux entrances in superconductors, the so-called ux avalanches, due to ...
Efeitos eletrônicos, elásticos e estruturais em sistemas semicondutores nanoscópicos
(Universidade Federal de São Carlos, 2012-02-16)
The present work aims the study of electronic, elastic and structural properties of a whole class of nanoscopic semiconductors systems, which include quasi-two-dimensional, one-dimensional and zero-dimensional confined ...
Espectroscopia Mössbauer : condições experimentais de aquisição e estocagem multicanal para a análise numérica de dados com adequação de resolução espectral
(Universidade Federal de São Carlos, 2012-02-15)
The objective of this work is to examine the use of Mossbauer spectroscopy in two aspects: the data acquisition, using four different setups and their analysis, comparing three different fittings programs. Concerning to ...
Efeito Aharonov-Bohm em partículas neutras
(Universidade Federal de São Carlos, 2011-03-14)
In classical Physics, the motion of an electrically charged particle is affected only by the presence of a magnetic field if the particle enters a region of space in which the field is present. Meanwhile, in quantum Physics, ...