On August 17, 2017, humankind for the first time detected a gravitational wave source due to a binary neutron star merger. It was followed by a short duration gamma-ray burst 1.7 seconds afterwards. Bing Zhang discussed the astrophysical origin of this 1.7-second delay, which holds the key to unveil the mystery of the formation, propagation, and emission of the relativistic jet launched from such a system. For more details, please refer to the article “[Detail] ...” by Bing Zhang, Front. Phys. 14(6), 64402 (2019). [Photo credits: National Science Foundation/LIGO/Sonoma State University/A. Simonnet.]
The first gravitational wave (GW) – gamma-ray burst (GRB) association, GW170817/GRB 170817A, had an offset in time, with the GRB trigger time delayed by ~1.7 s with respect to the merger time of the GW signal. We generally discuss the astrophysical origin of the delay time, Δt, of GW-GRB associations within the context of compact binary coalescence (CBC) – short GRB (sGRB) associations and GW burst – long GRB (lGRB) associations. In general, the delay time should include three terms, the time to launch a clean (relativistic) jet, Δtjet; the time for the jet to break out from the surrounding medium, Δtbo; and the time for the jet to reach the energy dissipation and GRB emission site, ΔtGRB. For CBC-sGRB associations, Δtjet and Δtbo are correlated, and the final delay can be from 10 ms to a few seconds. For GWB-lGRB associations, Δtjet and Δtbo are independent. The latter is at least ~10 s, so that Δt of these associations is at least this long. For certain jet launching mechanisms of lGRBs, Δt can be minutes or even hours long due to the extended engine waiting time to launch a jet. We discuss the cases of GW170817/GRB 170817A and GW150914/GW150914-GBM within this theoretical framework and suggest that the delay times of future GW/GRB associations will shed light into the jet launching mechanisms of GRBs.
Recently, the BESIII collaboration has reported numerous measurements of various D(s) meson semileptonic decays with significantly improved precision. Together with similar studies carried out at BABAR, Belle, and CLEO, new windows to a better understanding of weak and strong interactions in the charm sector have been opened. In light of new experimental data, we review the theoretical description and predictions for the semileptonic decays of D(s) to a pseudoscalar or a vector meson. This review is essentially an extended discussion of our recently published results obtained in the framework of the covariant confining quark model.
Fe-Ni core-shell nanoparticles are versatile functional materials, and their thermal stabilities are crucial for their performances in operating conditions. In this study, the thermodynamic behaviors of Fe-Ni core-shell nanoparticles are examined under continuous heating. The solid–solid phase transition from body centered cubic (bcc) to face centered cubic (fcc) in the Fe core is identified. The transition is accompanied with the generation of stacking faults around the core-shell interface, which notably lowers the melting points of the Fe-Ni core-shell nanoparticles and causes even worse thermal stability compared with Ni ones. Moreover, the temperature of the structural transformation is shown to be tuned by modifying the Ni shell thickness. Finally, the stress distributions of the core and the shell are also explored. The relevant results could be helpful for the design, preparation, and utilization of Fe-based nanomaterials.
We theoretically investigate the conductance fluctuation of two-terminal device in Sierpinski carpets. We find that, for the circular orthogonal ensemble (COE), the conductance fluctuation does not display a universal feature; but for circular unitary ensemble (CUE) without time-reversal symmetry or circular symplectic ensemble (CSE) without spin-rotational symmetry, the conductance fluctuation can reach an identical universal value of 0.74±0.01(e2/h). We further find that the conductance distributions around the critical disorder strength for both CUE and CSE systems share the similar distribution forms. Our findings provide a better understanding of the electronic transport properties of the regular fractal structure.
Magneto-transport study has been performed in topological semimetal ZrSiS single crystals under high pulsed magnetic fields. Obvious dependence of Landau level splitting on temperature and angular was investigated. The strong three-dimensional anisotropic nature of Landau level splitting under high pulsed magnetic fields was revealed by the angular dependent measurements, in which the orbital contribution is more dominant than Zeeman splitting. Our studies provide more insights into the physical properties of topological semimetals ZrSiS and shed light on future spintronic applications of ZrSiS.
We report an experimental investigation of the influence of surface charges on the emission polarization properties of single CdSe/CdS dot-in-rods (DRs), which is important for their polarization-based practical applications. By covering the single DRs with N-type semiconductor indium tin oxide (ITO) nanoparticles, the surface of single DRs is charged by ITO through interfacial electron transfer. This is confirmed by the experimental observations of the reduced photoluminescence intensities and lifetimes as well as the suppressing blinking. It is found that the full width at half maximum of histogram of polarization degrees of the single DRs is broadened from 0.24 (on glass) to 0.41 (in ITO). In order to explain the exprimental results, the band-edge exciton fine structure of single DRs is calculated by taking into account the sample parameters, the emission polarization, and the surface charges. The calculation results show that the level ordering of the emitting states determines the polarization degrees tending to increase or decrease under the influence of surface electrons. The surface electrons can induce an increase in the spacing between the emitting levels to change the populations and thus change the polarization degrees. In addition, different numbers of surface electrons may randomly distribute on the long CdSe/CdS rods, leading to the heterogeneous influences on the single DRs causing the broadening of polarization degrees also.
This collection presents 505 papers on ferroelectricity in single crystals, ceramics and polymers in which pointed or elliptical hysteresis loops would testify to their ferroelectric properties. In some papers, the authors ensure that ferroelectricity can occur even in materials that do not have a polar axis of symmetry.
We proposed and demonstrated that PT symmetric metamaterials could be used to achieve enhanced spin Hall effect (SHE) of light. We find that when laser mode is excited in PT symmetric system, the enhanced SHE could be obtained in both transmitted and reflected beams. In addition, as exceptional points (EPs) of PT symmetric system can happen for both p- and s-polarizations, the enhanced SHE of reflected light can function for both horizontally and vertically polarized incident beams. Particularly, these EPs can lead to unidirectional reflectionlessness, asymmetric SHE with maximum contrast ratio of 48 is obtained by launching light beams near EPs. Our work opens up a new path to obtain enhanced transverse displacement for both reflected and transmitted light and enables more opportunities in manipulating photonic SHE.
In this paper we redesign the probabilistic teleportation scheme considered in Phys. Rev. A 61, 034301 (2000) by Wan-Li Li et al., where the optimal state extraction protocolcomplements the basic teleportation process with a partially entangled pure state channel, in order to transfer the unknown state with fidelity 1. Unlike that scheme, where the information of the unknown state is lost if the state extraction fails, our proposal teleports exactly and optimally an unknown state, and allows to recover faithfully that state when the process has not succeeded. In order to study the resilience of the scheme, we apply it to the teleportation problem through a quantum channel in a mixed state with pure dephasing. We find that a successful process transfers an unfaithful state, namely, the outcome state acquires the decoherence of the channel, but the unknown state is recovered by the sender with fidelity 1 if the teleportation fails. In addition, in this case, the fidelity of the teleported state has quantum features only if the channel has an amount of entanglement different from zero.
In the context of the quantum-mechanical description of single-molecule surface-enhanced Raman scattering, intensity-field correlation measurements of photons emitted from a plasmonic cavity are explored, theoretically, using the technique of conditional homodyne detection. The inelastic interplay between plasmons and vibrations of a diatomic molecule placed inside the cavity can be manifested in phase-dependent third-order fluctuations of the light recorded by the aforesaid technique, allowing us to reveal signatures of non-classicality (indicatives of squeezing) of the outgoing Raman photons.