4,451 research outputs found
Fundamental Band Gap and Alignment of Two-Dimensional Semiconductors Explored by Machine Learning
Two-dimensional (2D) semiconductors isoelectronic to phosphorene has been
drawing much attention recently due to their promising applications for
next-generation (opt)electronics. This family of 2D materials contains more
than 400 members, including (a) elemental group-V materials, (b) binary III-VII
and IV-VI compounds, (c) ternary III-VI-VII and IV-V-VII compounds, making
materials design with targeted functionality unprecedentedly rich and extremely
challenging. To shed light on rational functionality design with this family of
materials, we systemically explore their fundamental band gaps and alignments
using hybrid density functional theory (DFT) in combination with machine
learning. First, GGA-PBE and HSE calculations are performed as a reference. We
find this family of materials share similar crystalline structures, but possess
largely distributed band-gap values ranging approximately from 0 to 8 eV. Then,
we apply machine learning methods, including Linear Regression (LR), Random
Forest Regression (RFR), and Support Vector Machine Regression (SVR), to build
models for prediction of electronic properties. Among these models, SVR is
found to have the best performance, yielding the root mean square error (RMSE)
less than 0.15 eV for predicted band gaps, VBMs, and CBMs when both PBE results
and elemental information are used as features. Thus, we demonstrate machine
learning models are universally suitable for screening 2D isoelectronic systems
with targeted functionality and especially valuable for the design of alloys
and heterogeneous systems.Comment: 6 figure
Final State Interactions in decays
The two-body nonleptonic charmed meson decays into two pseudoscalar mesons
are studied using one-particle-exchange method. The effects of the final state
interactions are analyzed through the strong phases extracted from the
experimental data.Comment: 15 pages, 7 figure
asymmetry in the angular distribution of decays
In this work, we study the asymmetry in the angular distribution of
decays, taking into account the known violation
in mixing. It is pointed out for the first time that, once the
well-measured violation in the neutral kaon system is invoked, a non-zero
asymmetry would appear in the angular observable of the decays considered,
even within the Standard Model. By employing the reciprocal basis, which is
most convenient when a is involved in the final state, the
-violating angular observable is derived to be two times the product of the
time-dependent asymmetry in and the mean value of the
angular distribution in decays. Compared with the Belle
results measured in four different bins of the invariant mass, our
predictions lie within the margins of these measurements, except for a
deviation for the lowest mass bin. While being below the current
Belle detection sensitivity that is of , our predictions
are expected to be detectable at the Belle II experiment, where
times more sensitive results will be obtained with a data
sample.Comment: 23 pages, 3 figures, and 2 tables; minor corrections, final version
published in the journa
Strong light illumination on gain-switched semiconductor lasers helps the eavesdropper in practical quantum key distribution systems
The temperature of the semiconductor diode increases under strong light
illumination whether thermoelectric cooler is installed or not, which changes
the output wavelength of the laser (Lee M. S. et al., 2017). However, other
characteristics also vary as temperature increases. These variations may help
the eavesdropper in practical quantum key distribution systems. We study the
effects of temperature increase on gain-switched semiconductor lasers by
simulating temperature dependent rate equations. The results show that
temperature increase may cause large intensity fluctuation, decrease the output
intensity and lead the signal state and decoy state distinguishable. We also
propose a modified photon number splitting attack by exploiting the effects of
temperature increase. Countermeasures are also proposed.Comment: Accepted by Optics Communications. 7 Figure
Recovering the lost steerability of quantum states within non-Markovian environments by utilizing quantum partially collapsing measurements
In this Letter, we mainly investigate the dynamic behavior of quantum
steering and how to effectively recover the lost steerability of quantum states
within non-Markovian environments. We consider two different cases
(one-subsystem or all-subsystem interacts with the dissipative environments),
and obtain that the dynamical interaction between system initialized by a
Werner state and the non-Markovian environments can induce the quasi-periodic
quantum entanglement (concurrence) resurgence, however, quantum steering cannot
retrieve in such a condition. And we can obtain that the resurgent quantum
entanglement cannot be utilized to achieve quantum steering. Subsequently, we
put forward a feasible physical scheme for recovering the steerability of
quantum states within the non-Markovian noises by prior weak measurement on
each subsystem before the interaction with dissipative environments followed by
post weak measurement reversal. It is shown that the steerability of quantum
states and the fidelity can be effectively restored. Furthermore, the results
show that the larger the weak measurement strength is, the better the
effectiveness of the scheme is. Consequently, our investigations might be
beneficial to recover the lost steerability of quantum states within the
non-Markovian regimes.Comment: Accepted for publication in Laser Physics Letters.17 pages, 8 figure
CP-violation for B --> Xll including long-distance effects
We consider the CP violating effect for B\to X_sl^+l^- process, including both short and long distance effects. We obtain the CP asymmetry parameter and present its variation over the dilepton mass
Electroweak Penguin Effects In Some Two-Body Decays
Using the next-to-leading order low energy effective Hamiltonian for transitions, the effects of electroweak penguin operators in some two-body
decay modes of meson are estimated in the Standard Model (SM). We find
that in and decay modes, the electroweak
penguin effects are small, while in , ,
, the electroweak penguin operators enhance or reduce the pure QCD
penguin and tree level contributions by in decay width. We also
present the results of CP asymmetries in these deacy modes.Comment: 12 pages, no figur
Study of the isospin breaking decay at BESIII
Using measured branching fraction of the decay from the
BESIII experiment, we estimate branching fraction of decay,
which proceeds via the - mixing and the -
mixing. The branching fraction is predicted to be about , which can
be accessed with events collected at the BESIII. The decay
is dominated by the contribution from - mixing. We find
that the interference between the amplitudes due to -
mixing and that due to - mixing is destructive. The branching
fraction can be decreased by about owing to the interference effect. We
also study the mass squared spectrum, and find that a narrow peak
due to the - mixing in the mass squared
spectrum should be observed. The observation of this decay in experiment will
be helpful to determine the - mixing intensity and get
information about the structures of the light scalar mesons.Comment: 16 pages, 3 figure
Universal trade-off relation between coherence and intrinsic concurrence for two-qubit states
Entanglement and coherence are two essential quantum resources for quantum
information processing. A natural question arises of whether there are direct
link between them. And by thinking about this question, we propose a new
measure for quantum state that contains concurrence and is called intrinsic
concurrence. Interestingly, we discover that the intrinsic concurrence is
always complementary to coherence. Note that the intrinsic concurrence is
related to the concurrence of a special pure state ensemble. In order to
explain the trade-off relation more intuitively, we apply it in some composite
systems composed by a single-qubit state coupling four typical noise channels
with the aim at illustrating their mutual transformation relationship between
their coherence and intrinsic concurrence. This unified trade-off relation will
provide more flexibility in exploiting one resource to perform quantum tasks
and also provide credible theoretical basis for the interconversion of the two
important quantum resources.Comment: 7 pages, 1 figure
Study of decay in the light-cone sum rules approach
Within the QCD light-cone sum rule (LCSR) approach, we investigate the
transition form factors of up to the twist-3 light-cone
distribution amplitudes (LCDAs) of the scalar meson in the two-quark
picture. Using these form factors, we calculate the differential decay widths
and branching ratios of the semileptonic
decays. We obtain and . The results are
sensitive to the inner structure. These decays can be searched for
at BESIII experiment, and any experimental observations will be useful to
identify internal quark contents of the meson, which will shed light
on understanding theoretical models.Comment: 19 pages,5 figure
- …