Isospin of topological defects in Dirac systems
Sep, 2011Citations per year
Abstract: (arXiv)
We study the Dirac quasiparticles in -dimensional lattice systems of electrons in the presence of domain walls (), vortices (), or hedgehogs () of superconducting and/or insulating, order parameters, which appear as mass terms in the Dirac equation. Such topological defects have been known to carry non-trivial quantum numbers such as charge and spin. Here we discuss their additional internal degree of freedom: irrespectively of the dimensionality of space and the nature of orders that support the defect, an extra mass-order-parameter is found to emerge in their core. Six linearly independent local orders, which close two mutually commuting three-dimensional Clifford algebras are proven to be in general possible. We show how the particle-hole symmetry restricts the defects to always carry the quantum numbers of a single effective isospin-1/2, quite independently of the values of their electric charge or true spin. Examples of this new degree of freedom in graphene and on surfaces of topological insulators are discussed.Note:
- 7 PRB pages, one table, one figure/ thoroughly revised and extended version, more discussion of physical examples in graphene and topological insulator surface, two Appendices with mathematical details, many new references/ several typos corrected, published version
- 71.10.Li
- 74.20.Rp
- 71.10.Pm
- 72.80.Vp
References(19)
Figures(2)