title: Coexisting edge states and gapless bulk in topological states of matter.
abstract: We consider two-dimensional systems in which edge states coexist with a gapless bulk. Such systems may be constructed, for example, by coupling a gapped two-dimensional state of matter that carries edge states to a gapless two-dimensional system in which the spectrum is composed of a number of Dirac cones. We find that, in the absence of disorder, the edge states could be protected even when the two systems are coupled, due to momentum and energy conservation. We distinguish between weak and strong edge states by the level of their mixing with the bulk. In the presence of disorder, the edge states may be stabilized when the bulk is localized or destabilized when the bulk is metallic. We analyze the conditions under which these two cases occur. Finally, we propose a concrete physical realization for one of our models based on bilayer Hg(Cd)Te quantum wells.
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Baum
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany.
authors.forename: Thore
authors.initials: T
authors.lastname: Posske
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ion Cosma
authors.initials: IC
authors.lastname: Fulga
authors.affiliation: Institut für Theoretische Physik und Astrophysik, Universität Würzburg, 97074 Würzburg, Germany.
authors.forename: Björn
authors.initials: B
authors.lastname: Trauzettel
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Ady
authors.initials: A
authors.lastname: Stern