AAPPS Bulletin最新文献

Bandpass filters with high frequency and wide bandwidth are indispensable parts of the fifth-generation telecommunication technologies, and currently, they are mainly based on surface and bulk acoustic wave resonators. Owing to its high mechanical strength, excellent stability at elevated temperatures, good thermal conductivity, and compatibility with complementary metal-oxide-semiconductor technology, aluminum nitride (AlN) becomes the primary piezoelectric material for high-frequency resonators. This review briefly introduces the structures and key performance parameters of the acoustic resonators. The common filter topologies are also discussed. In particular, research progresses in the piezoelectric AlN layer, electrodes, and substrates of the resonators are elaborated. Increasing the electromechanical coupling constant is the main concern for the AlN film. To synthesize AlN in single-crystalline or poly-crystalline with a high intensity of (0002) orientation, and alloy the AlN with other elements are two effective approaches. For the substrates and bottom electrodes, lattice and thermal expansion mismatch, and surface roughness are critical for the synthesis of a high-crystal-quality piezoelectric layer. The electrodes with low electrical resistance, large acoustic-impedance mismatch to the piezoelectric layer, and low density are ideal to reduce insertion loss. Based on the research progress, several possible research directions in the AlN-based filters are suggested at the end of the paper.

Solving linear differential equations is a common problem in almost all fields of science and engineering. Here, we present a variational algorithm with shallow circuits for solving such a problem: given an (N times N) matrix ({varvec{A}}), an N-dimensional vector (varvec{b}), and an initial vector (varvec{x}(0)), how to obtain the solution vector (varvec{x}(T)) at time T according to the constraint (textrm{d}varvec{x}(t)/textrm{d} t = {varvec{A}}varvec{x}(t) + varvec{b}). The core idea of the algorithm is to encode the equations into a ground state problem of the Hamiltonian, which is solved via hybrid quantum-classical methods with high fidelities. Compared with the previous works, our algorithm requires the least qubit resources and can restore the entire evolutionary process. In particular, we show its application in simulating the evolution of harmonic oscillators and dynamics of non-Hermitian systems with (mathcal{P}mathcal{T})-symmetry. Our algorithm framework provides a key technique for solving so many important problems whose essence is the solution of linear differential equations.

The angular distance of the solar flares to the projective point of the center of the solar disk on the solar spherical surface has been studied by the heliographical or helioprojective coordinates, during the periods 1975–2021 for GOES events and 2002–2021 for RHESSI events, hereafter “distance.” It gives a specific distribution curvature. It has also been noted that when using the number of solar flare events in each satellite, GOES or RHESSI, or even using the sum of the flux (class) or importance parameter, it obtains the same result, which is that the shape of the distribution curve remains in its shape without any significant change. In addition, it has been shown that the distribution curve contains a specific number of peaks. These peaks have a specific distance from the center of the solar disk that is very similar to the projection of the solar interior layers on the solar disk. For this reason, the names of these four main peaks have been given as follows: (1) the core circle (0–15°): it is a projection of the solar core onto the solar disk, (2) radiative ring (15–45°), and (3) the convection ring (45–55°). The limb ring is 80–90°. This result makes us wonder why the number of events in the middle of the solar disk is few, and also small at the solar limb, while many in the other parts in the solar disk. This suggests that we need to understand the sun better than before, and it also suggests that solar flares are connected to each other through the solar interior layers, the extent of which may reach the convection zone or perhaps beyond that, or the opacity of the convection zone may be less than the currently estimated value.

Neutron star observations, as well as experiments on neutron-rich nuclei, used to motivate one to look at degenerate nuclear matter from its extreme, namely, pure neutron matter. As an important next step, impurities and clusters in dilute neutron matter have attracted special attention. In this paper, we review in-medium properties of these objects on the basis of the physics of polarons, which have been recently realized in ultracold atomic experiments. We discuss how such atomic and nuclear systems are related to each other in terms of polarons. In addition to the interdisciplinary understanding of in-medium nuclear clusters, it is shown that the quasiparticle energy of a single proton in neutron matter is associated with the symmetry energy, implying a novel route toward the nuclear equation of state from the neutron-rich side.

Excited states are essential to many chemical processes in photosynthesis, solar cells, light-emitting diodes, and so on, yet how to formulate, quantify, and predict physiochemical properties for excited states from the theoretical perspective is far from being established. In this work, we leverage the four density-based frameworks from density functional theory (DFT) including orbital-free DFT, conceptual DFT, information-theoretic approach and direct use of density associated descriptors and apply them to the lowest singlet and triplet excited states for a variety of molecular systems to examine their stability, bonding, and reactivity propensities. Our results from the present study elucidate that it is feasible to employ these density-based frameworks to appreciate physiochemical properties for excited states and that excited state propensities can be markedly different from, sometime completely opposite to, those in the ground state. This work is the first effort, to the best of our knowledge, utilizing density-based reactivity frameworks to excited state. It should offer ample opportunities in the future to deal with real-world problems in photophysical and photochemical processes and transformations.

Graphical Abstract

Electric dipole (E1) and spin-magnetic dipole (spin-M1) responses of nuclei have been studied by proton inelastic scattering experiments at forward angles, including zero degrees, at the Research Center for Nuclear Physics (RCNP) by employing a proton beam 295 or 392 MeV and the high-resolution magnetic spectrometer Grand Raiden. The E1 response of nuclei is the most fundamental nuclear response to the external field and is relevant to photo-nuclear reactions. After introducing the relevant nuclear matrix elements and the experimental methods, several recent experimental works are highlighted that include (E1) polarizability and the extraction of the symmetry energy parameters, pygmy dipole resonance, gamma-coincidence measurements, isoscalar and isovector spin-M1 excitations and the np spin correlation in the ground state, and gamma-emission probability for neutral current neutrino detection. A project, PANDORA, is introduced that aims at a systematic study of photo-nuclear reactions and decay branching ratios for light nuclei.

A molecular rotor is a molecule/molecular system that performs rotary motions under an external stimulus. Molecular rotors are promising for applications in medicine, optical usage, information science, etc. A molecular rotor is also a crucial component in constructing more sophisticated functional molecular machines. Anchoring molecular rotors on surfaces is regarded as a feasible way of building functional molecular rotor systems. Scanning tunneling microscope (STM) is a powerful tool for studying surface dynamics in real space on atomic precision. It provides an ideal platform for both qualitatively and quantitively investigating single and self-assembled molecular rotors mounted on surfaces. Herein, we review a series of studies utilizing STM to unveil the methodologies that are increasingly used in the area of surface-mounted molecule rotors. A combined usage of these methodologies is more and more necessary for researchers to advance the molecular rotor study in future.

We study the hadronic coupling constants in the two-body strong decays of the fully-charm tetraquark states with the (J^{PC}=0^{++}), (1^{+-}), and (2^{++}) via the QCD sum rules based on rigorous quark-hadron duality. Then we obtain the hadronic coupling constants and partial decay widths therefore total decay widths, which support assigning the X(6552) as the first radial excitation of the scalar tetraquark state. And other predictions can be used to diagnose exotic states in the future.