21,140 research outputs found
Unconventional Quantum Hall Effect and Tunable Spin Hall Effect in MoS2 Trilayers
We analyze the Landau level (LL) structure and spin Hall effect in a MoS2
trilayer. Due to orbital asymmetry, the low-energy Dirac fermions become
heavily massive and the LL energies grow linearly with , rather than with
. Spin-orbital couplings break spin and valley degenerate LL's into
two time reversal invariant groups, with LL crossing effects present in the
valence bands. We find a field-dependent unconventional Hall plateau sequence
, , , , ..., -5, -3, -1, 0, 2, 4 .... In
a p-n junction, spin-resolved fractionally quantized conductance appears in
two-terminal measurements with a controllable spin-polarized current that can
be probed at the interface. We also show the tunability of zero-field spin Hall
conductivity.Comment: 5 pages, 4 figure
Designer Topological Insulators in Superlattices
Gapless Dirac surface states are protected at the interface of topological
and normal band insulators. In a binary superlattice bearing such interfaces,
we establish that valley-dependent dimerization of symmetry-unrelated Dirac
surface states can be exploited to induce topological quantum phase
transitions. This mechanism leads to a rich phase diagram that allows us to
design strong, weak, and crystalline topological insulators. Our ab initio
simulations further demonstrate this mechanism in [111] and [110] superlattices
of calcium and tin tellurides.Comment: 5 pages, 4 figure
Spontaneous Layer-Pseudospin Domain Walls in Bilayer Graphene
Bilayer graphene is susceptible to a family of unusual broken symmetry states
with spin and valley dependent layer polarization. We report on a microscopic
study of the domain walls in these systems, demonstrating that they have
interesting microscopic structures related to order-induced topological
characters. We use our results to estimate Ginzburg-Landau model parameters and
transition temperatures for the ordered states of bilayer graphene.Comment: 4 pages, 3 figure
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