Topological insulators are materials with a bulk band gap, but with topologically protected, spin polarized surface states with Dirac dispersion. Bi2Te3 is such a topological insulator with a single Dirac cone at the center of the Brillouin zone. ARPES studies have shown that the Fermi surface of Bi2Te3 changes from a circle to a hexagon, and then to a hexagram, when moving away from the Dirac ...

Three dimensional topological Dirac semi-metals represent a novel state of quantum matter with exotic electronic properties, in which a pair of Dirac points with the linear dispersion along all momentum directions exist in the bulk. Herein, by using the first principles calculations, we discover a new metastable allotrope of Ge and Sn in the staggered layered dumbbell structure, named as german...

Boltzmann relations are widely used in semiconductor physics to express the charge-carrier densities as a function of Fermi level and temperature. However, these simple exponential only apply sharp band edges conduction valence bands. In this article, we present generalization accounting for tails. To end, required Fermi-Dirac integral is first recast Gauss hypergeometric function, followed by ...

 The two-dimensional structure of graphene, consisting of an isotropic hexagonal lattice of carbon atoms, shows fascinating electronic properties, such as a gapless energy band and Dirac fermion behavior of electrons at fermi surface. Anisotropy can be induced in this structure by electrochemical pressure. In this article, by using tight-binding method, we review anisotropy effects in the elect...

We apply a recently proposed path-integral approach to non-local bosonization to a Thirring-like system modeling non-relativistic mass-less particles interacting with localized fermionic impurities. We consider forward scattering processes described by symmetric potentials including interactions between charge, current, spin and spin-current densities. In the general (spin-flipping) problem we ...

The application of the Bose-Einstein and Fermi-Dirac interferometry to multi-hadron final states of particle reactions is reviewed. The underlying theoretical concepts of particle interferometry is presented where a special emphasis is given to the recently proposed Fermi-Dirac correlation analysis. The experimental tools used for the interferometry analyses and the interpretation of their resu...

We show that the pseudorelativistic physics of graphene near the Fermi level can be extended to three dimensional (3D) materials. Unlike in phase transitions from inversion symmetric topological to normal insulators, we show that particular space groups also allow 3D Dirac points as symmetry protected degeneracies. We provide criteria necessary to identify these groups and, as an example, prese...

Diffusive moment equations with an arbitrary number of moments are formally derived from the semiconductor Boltzmann equation employing a moment method and a Chapman-Enskog expansion. The moment equations are closed by employing a generalized Fermi-Dirac distribution function obtained from entropy maximization. The current densities allow for a drift-diffusion-type formulation or a “symmetrized...

A hexagonal deformation of the Fermi surface of Bi2Se3 has been for the first time observed by angle-resolved photoemission spectroscopy. This is in contrast to the general belief that Bi2Se3 possesses an ideal Dirac cone. The hexagonal shape is found to disappear near the Dirac node, which would protect the surface state electrons from backscattering. It is also demonstrated that the Fermi ene...

In addition to a bulk energy gap, topological insulators accommodate a conducting, linearly dispersed Dirac surface state. This state is predicted to become massive if time reversal symmetry is broken, and to become insulating if the Fermi energy is positioned inside both the surface and bulk gaps. We introduced magnetic dopants into the three-dimensional topological insulator dibismuth trisele...