69 research outputs found
Robust one-dimensional wires in lattice mismatched bilayer graphene
We show that lattice mismatched bilayer graphene can realize robust
one-dimensional wires. By considering a single domain wall where the masses of
the Dirac electrons change their sign, we establish a general projection
principle. This determines how the existence of topological zero-energy domain
wall states depends on the direction of the domain wall and locations of the
massive Dirac cones inside the bulk Brillouin zone. We generalize this idea for
arbitrary patterns of domain walls, showing that the topologically protected
states exist only in the presence of an odd number of topological domain walls.Comment: 8 preprint pages, 3 figure
Zeeman field induced topological phase transitions in triplet superconductors
We develop a general Ginzburg-Landau theory which describes the effect of a
Zeeman field on the superconducting order parameter in triplet superconductors.
Starting from Ginzburg-Landau theories that describe fully gapped time-reversal
symmetric triplet superconductors, we show that the Zeeman field has dramatic
effects on the topological properties of the superconductors. In particular, in
the vicinity of a critical chemical potential separating two topologically
distinct phases, it is possible to induce a phase transition to a topologically
nontrivial phase which supports chiral edge modes. Moreover, for specific
directions of the Zeeman field, we obtain nodal superconducting phases with an
emerging chiral symmetry, and with Majorana flat bands at the edge. The
Ginzburg-Landau theory is microscopically supported by a self-consistent
mean-field theory of the doped Kitaev-Heisenberg model
Symmetry-protected topological invariant and Majorana impurity states in time-reversal-invariant superconductors
We address the question of whether individual nonmagnetic impurities can
induce zero-energy states in time-reversal-invariant topological
superconductors, and define a class of symmetries which guarantee the existence
of such states for a specific value of the impurity strength. These symmetries
allow the definition of a position-space topological Z_2 invariant, which is
related to the standard bulk topological Z_2 invariant. Our general results are
applied to the time-reversal-invariant p-wave phase of the doped
Kitaev-Heisenberg model, where we demonstrate how a lattice of impurities can
drive a topologically trivial system into the nontrivial phase.Comment: published versio
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