19,260 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
Hadronic Decays Involving Heavy Pentaquarks
Recently several experiments have reported evidences for pentaquark
. H1 experiment at HERA-B has also reported evidence for .
is interpreted as a bound state of an with other four light
quarks which is a member of the anti-decuplet under flavor .
While is a state by replacing the in by a . One can also form by replacing the by a . The
charmed and bottomed heavy pentaquarks form triplets and anti-sixtets under
. We study decay processes involving at least one heavy pentaquark
using and estimate the decay widths for some decay modes. We find
several relations for heavy pentaquarks decay into another heavy pentaquark and
a or a which can be tested in the future. can decay
through weak interaction to charmed heavy pentaquarks. We also study some
decay modes with a heavy pebtaquark in the final states. Experiments at the
current factories can provide important information about the heavy
pentaquark properties.Comment: RevTex 20 pages. Revised version. Discussions on the recent H1 data
and new references adde
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
Giant and tunable valley degeneracy splitting in MoTe2
Monolayer transition-metal dichalcogenides possess a pair of degenerate
helical valleys in the band structure that exhibit fascinating optical valley
polarization. Optical valley polarization, however, is limited by carrier
lifetimes of these materials. Lifting the valley degeneracy is therefore an
attractive route for achieving valley polarization. It is very challenging to
achieve appreciable valley degeneracy splitting with applied magnetic field. We
propose a strategy to create giant splitting of the valley degeneracy by
proximity-induced Zeeman effect. As a demonstration, our first principles
calculations of monolayer MoTe on a EuO substrate show that valley
splitting over 300 meV can be generated. The proximity coupling also makes
interband transition energies valley dependent, enabling valley selection by
optical frequency tuning in addition to circular polarization. The valley
splitting in the heterostructure is also continuously tunable by rotating
substrate magnetization. The giant and tunable valley splitting adds a readily
accessible dimension to the valley-spin physics with rich and interesting
experimental consequences, and offers a practical avenue for exploring device
paradigms based on the intrinsic degrees of freedom of electrons.Comment: 8 pages, 5 figures, 1 tabl
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
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