162 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
Importance of bath dynamics for decoherence in spin systems
We study the decoherence of two coupled spins that interact with a chaotic
spin-bath environment. It is shown that connectivity of spins in the bath is of
crucial importance for the decoherence of the central system. The previously
found phenomenon of two-step decoherence (Phys. Rev. Lett. {\bf 90}, 210401
(2003)) turns out to be typical for the bath with a slow enough dynamics or no
dynamics. For a generic random system with chaotic dynamics a conventional
exponential relaxation to the pointer states takes place. Our results confirm a
conjecture of Paz and Zurek (Phys. Rev. Lett. {\bf 82}, 5181 (1999)) that for
weak enough interactions the pointer states are eigenstates of the central
system.Comment: submitted to Physical Review Letter
Toward a realistic description of multilayer black phosphorus: from approximation to large-scale tight-binding simulations
We provide a tight-binding model parametrization for black phosphorus (BP)
with an arbitrary number of layers. The model is derived from partially
self-consistent approach, where the screened Coulomb interaction
is calculated within the random phase approximation on the basis of density
functional theory. We thoroughly validate the model by performing a series of
benchmark calculations, and determine the limits of its applicability. The
application of the model to the calculations of electronic and optical
properties of multilayer BP demonstrates good quantitative agreement with
\emph{ab initio} results in a wide energy range. We also show that the proposed
model can be easily extended for the case of external fields, yielding the
results consistent with those obtained from first principles. The model is
expected to be suitable for a variety of realistic problems related to the
electronic properties of multilayer BP including different kinds of disorder,
external fields, and many-body effects.Comment: 10 pages, 9 figures, 2 tables (final version, minor changes
Power-law energy level-spacing distributions in fractals
In this article we investigate the energy spectrum statistics of fractals at
the quantum level. We show that the energy-level distribution of a fractal
follows a power-law behaviour, if its energy spectrum is a limit set of
piece-wise linear functions. We propose that such a behaviour is a general
feature of fractals, which can not be described properly by random matrix
theory. Several other arguments for the power-law behaviour of the energy
level-spacing distributions are proposed
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
Landau Level Spectrum of ABA- and ABC-stacked Trilayer Graphene
We study the Landau level spectrum of ABA- and ABC-stacked trilayer graphene.
We derive analytic low energy expressions for the spectrum, the validity of
which is confirmed by comparison to a \pi -band tight-binding calculation of
the density of states on the honeycomb lattice. We further study the effect of
a perpendicular electric field on the spectrum, where a zero-energy plateau
appears for ABC stacking order, due to the opening of a gap at the Dirac point,
while the ABA-stacked trilayer graphene remains metallic. We discuss our
results in the context of recent electronic transport experiments. Furthermore,
we argue that the expressions obtained can be useful in the analysis of future
measurements of cyclotron resonance of electrons and holes in trilayer
graphene.Comment: 10 pages, 8 figure
Plasmon confinement in fractal quantum systems
Recent progress in the fabrication of materials has made it possible to
create arbitrary non-periodic two-dimensional structures in the quantum plasmon
regime. This paves the way for exploring the plasmonic properties of electron
gases in complex geometries such as fractals. In this work, we study the
plasmonic properties of Sierpinski carpets and gaskets, two prototypical
fractals with different ramification, by fully calculating their dielectric
functions. We show that the Sierpinski carpet has a dispersion comparable to a
square lattice, but the Sierpinski gasket features highly localized plasmon
modes with a flat dispersion. This strong plasmon confinement in finitely
ramified fractals can provide a novel setting for manipulating light at the
quantum scale.Comment: 5 pages, 4 figures, comments are welcom
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