Spin injection from a half-metallic electrode in the presence of thermal spin disorder is analyzed using a combination of random matrix theory, spin-diffusion theory, and explicit simulations for the tight-binding s-d model. It is shown that efficient spin injection from a half-metal is possible as long as the effective resistance of the normal metal does not exceed a characteristic value, whic...

O modelo de tight-binding é um dos pilares da Física Matéria Condensada, permitindo descrever forma bastante simples uma ampla gama fenômenos interesse, como por exemplo a estrutura bandas materiais e o transporte eletrônico. Nesse trabalho, Hamiltoniano tight-binding, escrito em linguagem segunda quantização, utilizado na modelagem das densidades estados energia polímeros orgânicos. procedimen...

We have developed a third-neighbor tight-binding model, with spin-orbit coupling included, to treat the electronic properties of Bi and Sb. This model successfully reproduces the features near the Fermi surface that will be most important in semimetal-semiconductor device structures, including (a) the small overlap of valence and conduction bands, (b) the electron and hole efFective masses, and...

Models for the integer quantum Hall effect: the network model, the Dirac equation, and a tight-binding Hamiltonian. Abstract We consider models for the plateau transition in the integer quantum Hall effect. Starting from the network model, we construct a mapping to the Dirac Hamiltonian in two dimensions. In the general case, the Dirac Hamiltonian has randomness in the mass, the scalar potentia...

We consider the system of two interacting atoms confined in axially symmetric harmonic trap. Within the pseudopotential approximation, we solve the Schrödinger equation exactly, discussing the limits of quasi-oneand quasi-two-dimensional geometries. Finally, we discuss the application of an energy-dependent pseudopotential, which allows us to extend the validity of our results to the case of ti...

We examine the requirements placed upon the Hamiltonian under the demand of gauge invariance. From these requirements we derive the gauge-invariant form of the tight-binding Hamiltonian with electromagnetic coupling. In our derivation we do not make recourse to a Peierls substitution and hence avoid introducing any ambiguities of path. Our expression transparently reduces to the familiar expres...