40,656 research outputs found
Crystal growth and quantum oscillations in the topological chiral semimetal CoSi
We survey the electrical transport properties of the single-crystalline,
topological chiral semimetal CoSi which was grown via different methods.
High-quality CoSi single crystals were found in the growth from tellurium
solution. The sample's high carrier mobility enables us to observe, for the
first time, quantum oscillations (QOs) in its thermoelectrical signals. Our
analysis of QOs reveals two spherical Fermi surfaces around the R point in the
Brillouin zone corner. The extracted Berry phases of these electron orbits are
consistent with the -2 chiral charge as reported in DFT calculations. Detailed
analysis on the QOs reveals that the spin-orbit coupling induced band-splitting
is less than 2 meV near the Fermi level, one order of magnitude smaller than
our DFT calculation result. We also report the phonon-drag induced large Nernst
effect in CoSi at intermediate temperatures
Two-component model for the chemical evolution of the Galactic disk
In the present paper, we introduce a two-component model of the Galactic disk
to investigate its chemical evolution. The formation of the thick and thin
disks occur in two main accretion episodes with both infall rates to be
Gaussian. Both the pre-thin and post-thin scenarios for the formation of the
Galactic disk are considered. The best-fitting is obtained through
-test between the models and the new observed metallicity distribution
function of G dwarfs in the solar neighbourhood (Hou et al 1998). Our results
show that post-thin disk scenario for the formation of the Galactic disk should
be preferred. Still, other comparison between model predictions and
observations are given.Comment: 23 pages, 7 figure
Fractional Quantum Hall Effect in Topological Flat Bands with Chern Number Two
Recent theoretical works have demonstrated various robust Abelian and
non-Abelian fractional topological phases in lattice models with topological
flat bands carrying Chern number C=1. Here we study hard-core bosons and
interacting fermions in a three-band triangular-lattice model with the lowest
topological flat band of Chern number C=2. We find convincing numerical
evidence of bosonic fractional quantum Hall effect at the filling
characterized by three-fold quasi-degeneracy of ground states on a torus, a
fractional Chern number for each ground state, a robust spectrum gap, and a gap
in quasihole excitation spectrum. We also observe numerical evidence of a
robust fermionic fractional quantum Hall effect for spinless fermions at the
filling with short-range interactions.Comment: 5 pages, 7 figures, with Supplementary Materia
Electron Delocalization in Gate-Tunable Gapless Silicene
The application of a perpendicular electric field can drive silicene into a
gapless state, characterized by two nearly fully spin-polarized Dirac cones
owing to both relatively large spin-orbital interactions and inversion symmetry
breaking. Here we argue that since inter-valley scattering from non-magnetic
impurities is highly suppressed by time reversal symmetry, the physics should
be effectively single-Dirac-cone like. Through numerical calculations, we
demonstrate that there is no significant backscattering from a single impurity
that is non-magnetic and unit-cell uniform, indicating a stable delocalized
state. This conjecture is then further confirmed from a scaling of conductance
for disordered systems using the same type of impurities.Comment: 6 pages, 3 figures, published versio
Binding Transition in Quantum Hall Edge States
We study a class of Abelian quantum Hall (QH) states which are topologically
unstable (T-unstable). We find that the T-unstable QH states can have a phase
transition on the edge which causes a binding between electrons and reduces the
number of gapless edge branches. After the binding transition, the
single-electron tunneling into the edge gains a finite energy gap, and only
certain multi-electron co-tunneling (such as three-electron co-tunneling for
edges) can be gapless. Similar phenomenon also appear for edge state
on the boundary between certain QH states. For example edge on the boundary
between and states only allow three-electron co-tunneling at
low energies after the binding transition.Comment: 4 pages, RevTeX, 1 figur
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