title: Spontaneous Breakdown of Topological Protection in Two Dimensions.
abstract: Because of time-reversal symmetry, two-dimensional topological insulators support counterpropagating helical edge modes. Here we show that, unlike the infinitely sharp edge potential utilized in traditional calculations, an experimentally more realistic smooth edge potential gives rise to edge reconstruction and, consequently, spontaneous time-reversal symmetry breaking. Such edge reconstruction may lead to breaking of the expected perfect conductance quantization, to a finite Hall resistance at zero magnetic field, and to a spin current. This calculation underpins the fragility of the topological protection in realistic systems, which is of crucial importance in proposed applications.
authors.affiliation: Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
authors.forename: Jianhui
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Physics, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.|Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel.
authors.forename: Yigal
authors.initials: Y
authors.lastname: Meir
authors.affiliation: Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Yuval
authors.initials: Y
authors.lastname: Gefen