Showing papers by "Eugene J. Mele published in 2012"
TL;DR: It is shown that the pseudorelativistic physics of graphene near the Fermi level can be extended to three dimensional materials and β-cristobalite BiO(2) is metastable, so it can be physically realized as a 3D analog to graphene.
Abstract: 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, present ab initio calculations of β-cristobalite BiO(2) which exhibits three Dirac points at the Fermi level. We find that β-cristobalite BiO(2) is metastable, so it can be physically realized as a 3D analog to graphene.
1,328 citations
01 Feb 2012
TL;DR: In this article, the pseudorelativistic physics of graphene near the Fermi level can be extended to three dimensional (3D) materials, and particular space groups also allow 3D Dirac points as symmetry protected degeneracies.
Abstract: 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, present ab initio calculations of β-cristobalite BiO(2) which exhibits three Dirac points at the Fermi level. We find that β-cristobalite BiO(2) is metastable, so it can be physically realized as a 3D analog to graphene.
763 citations
TL;DR: In this paper, a topological boundary condition was introduced to study the surface states of topological insulators within a long-wavelength four-band model, and it was shown that the Dirac point energy, the band curvature and the spin texture of surface states are crystal-face dependent.
Abstract: We introduce a topological boundary condition to study the surface states of topological insulators within a long-wavelength four-band model. We find that the Dirac point energy, the band curvature, and the spin texture of surface states are crystal-face dependent. For an arbitrary termination of a bulk crystal, the energy of the symmetry protected Dirac point is determined by the bulk physics that breaks particle-hole symmetry in the surface normal direction and is tunable by surface potentials that preserve time reversal symmetry. For a model appropriate to ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ the constant energy contours are generically elliptical with spin textures that are helical on the cleavage surface, collapsed to one dimension on any side face, and tilted out of plane otherwise. Our findings identify a route to engineering the Dirac point physics on the surfaces of real materials.
134 citations
TL;DR: In this paper, the Coulomb interactions between spinless charged solitons (interacting polarons which carry both spin and charge) were observed in polyacetylene and polyaniline (PANI) nanofibers.
Abstract: Polymer nanofibers are one-dimensional organic hydrocarbon systems containing conducting polymers where the non-linear local excitations such as solitons, polarons and bipolarons formed by the electron-phonon interaction were predicted. Magnetoconductance (MC) can simultaneously probe both the spin and charge of these mobile species and identify the effects of electron-electron interactions on these nonlinear excitations. Here we report our observations of a qualitatively different MC in polyacetylene (PA) and in polyaniline (PANI) and polythiophene (PT) nanofibers. In PA the MC is essentially zero, but it is present in PANI and PT. The universal scaling behavior and the zero (finite) MC in PA (PANI and PT) nanofibers provide evidence of Coulomb interactions between spinless charged solitons (interacting polarons which carry both spin and charge).
9 citations