18,329 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
Effects of density-dependent quark mass on phase diagram of three-flavor quark matter
Considering the density dependence of quark mass, we investigate the phase
transition between the (unpaired) strange quark matter and the
color-flavor-locked matter, which are supposed to be two candidates for the
ground state of strongly interacting matter. We find that if the current mass
of strange quark is small, the strange quark matter remains stable unless
the baryon density is very high. If is large, the phase transition from
the strange quark matter to the color-flavor-locked matter in particular to its
gapless phase is found to be different from the results predicted by previous
works. A complicated phase diagram of three-flavor quark matter is presented,
in which the color-flavor-locked phase region is suppressed for moderate
densities.Comment: 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
On A Proper Definition of Spin Current
The conventional definition of spin current is incomplete and unphysical in
describing spin transport in systems with spin-orbit coupling. A proper and
measurable spin current is established in this study, which fits well into the
standard framework of near-equilibrium transport theory and has the desirable
property to vanish in insulators with localized orbitals. Experimental
implications of our theory are discussed.Comment: Final version with updated journal-re
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