39,980 research outputs found
Tunable electronic and magneto-optical properties of monolayer arsenene from GW approximation to large-scale tight-binding simulations
Monolayers of group VA elements have attracted great attention with the
rising of black phosphorus. Here, we derive a simple tight-binding model for
monolayer grey arsenic, referred as arsenene (ML-As), based on the
first-principles calculations within the partially self-consistent GW0
approach. The resulting band structure derived from the six p-like orbitals
coincides with the quasi-particle energy from GW0 calculations with a high
accuracy. In the presence of a perpendicular magnetic field, ML-As exhibits two
sets of Landau levels linear with respect to the magnetic field and level
index. Our numerical calculation of the optical conductivity reveals that the
obtained optical gap is very close to the GW0 value and can be effectively
tuned by external magnetic field. Thus, our proposed TB model can be used for
further large-scale simulations of the electronic, optical and transport
properties of ML-As
Variation of Entanglement Entropy in Scattering Process
In a scattering process, the final state is determined by an initial state
and an S-matrix. We focus on two-particle scattering processes and consider the
entanglement between these particles. For two types initial states; i.e., an
unentangled state and an entangled one, we calculate perturbatively the change
of entanglement entropy from the initial state to the final one. Then we show a
few examples in a field theory and in quantum mechanics.Comment: 13 pages; v2: refs. adde
Partitioning technique for a discrete quantum system
We develop the partitioning technique for quantum discrete systems. The graph
consists of several subgraphs: a central graph and several branch graphs, with
each branch graph being rooted by an individual node on the central one. We
show that the effective Hamiltonian on the central graph can be constructed by
adding additional potentials on the branch-root nodes, which generates the same
result as does the the original Hamiltonian on the entire graph. Exactly
solvable models are presented to demonstrate the main points of this paper.Comment: 7 pages, 2 figure
Screening and plasmons in pure and disordered single- and bilayer black phosphorus
We study collective plasmon excitations and screening of disordered single-
and bilayer black phosphorus beyond the low energy continuum approximation. The
dynamical polarizability of phosphorene is computed using a tight-binding model
that properly accounts for the band structure in a wide energy range.
Electron-electron interaction is considered within the Random Phase
Approximation. Damping of the plasmon modes due to different kinds of disorder,
such as resonant scatterers and long-range disorder potentials, is analyzed. We
further show that an electric field applied perpendicular to bilayer
phosphorene can be used to tune the dispersion of the plasmon modes. For
sufficiently large electric field, the bilayer BP enters in a topological phase
with a characteristic plasmon spectrum, which is gaped in the armchair
direction.Comment: 9 pages, 9 figure
Analysis of hadronic invariant mass spectrum in inclusive charmless semileptonic B decays
We make an analysis of the hadronic invariant mass spectrum in inclusive
charmless semileptonic B meson decays in a QCD-based approach. The decay width
is studied as a function of the invariant mass cut. We examine their
sensitivities to the parameters of the theory. The theoretical uncertainties in
the determination of from the hadronic invariant mass spectrum are
investigated. A strategy for improving the theoretical accuracy in the value of
is described.Comment: 13 pages, 5 Postscript figure
High-quality Image Restoration from Partial Mixed Adaptive-Random Measurements
A novel framework to construct an efficient sensing (measurement) matrix,
called mixed adaptive-random (MAR) matrix, is introduced for directly acquiring
a compressed image representation. The mixed sampling (sensing) procedure
hybridizes adaptive edge measurements extracted from a low-resolution image
with uniform random measurements predefined for the high-resolution image to be
recovered. The mixed sensing matrix seamlessly captures important information
of an image, and meanwhile approximately satisfies the restricted isometry
property. To recover the high-resolution image from MAR measurements, the total
variation algorithm based on the compressive sensing theory is employed for
solving the Lagrangian regularization problem. Both peak signal-to-noise ratio
and structural similarity results demonstrate the MAR sensing framework shows
much better recovery performance than the completely random sensing one. The
work is particularly helpful for high-performance and lost-cost data
acquisition.Comment: 16 pages, 8 figure
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