Algumas contribuições ao estudo do Grafeno e dos Isolantes Topológicos

• Autor(a) principal: Fonseca, Jakson Miranda
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/957
• topic: Grafenos; Equação de Dirac; Fermions; Eletrodinâmica quântica; Isolantes topológicos; Graphene; Dirac equation; Fermions; Quantum electrodynamics; Topological insulators; CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA

In this thesis we study graphene and topological insulators. In the case of graphene, we study the scattering of quasiparticles by topological defects, represented by holes, pentagons and heptagons. For the case of holes, we obtain the phase shift and found that at low concentration they appear to be irrelevant for the electron transport, giving a negligible contribution to the resistivity. Whenever pentagons and heptagons are introduced into the lattice and the fermionic current is constrained to move near one of them we realize that such a current is scattered with an angle that depends on the number of pentagons and on the side the current taken. We consider the topological magnetoelectric effect on a conical topological insulator when a point charge q is near the cone apex. The Hall current induced on the cone surface is determined. We also study a kind of gravitational Aharonov-Bohm effect in this geometry and realize a phase diference betwen the components of the wavefunctions upon closed parallel transport around the cone tip. Concretely, a net current owing towards cone apex (or botton) shows up, yielding electric polarization of the conical topological insulator. Such an effect may be detected, for instance, by means of the net accumulated Hall charge near the apex. We also analyzed the modification induced on the surface spectrum when a topological insulator is coated with an ferromagnet with magnetization like-vortex. We consider the possibility of bound discrete states and unbound continuous states and found that a mass is not directly induced in the surface carriers.