AAPPS Bulletin最新文献

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.

Gravitational waves induced by large primordial curvature fluctuations may result in a sizable stochastic gravitational wave background. Interestingly, curvature fluctuations are gradually generated by initial isocurvature fluctuations, which in turn induce gravitational waves. Initial isocurvature fluctuations commonly appear in multi-field models of inflation as well as in the formation of scattered compact objects in the very early universe, such as primordial black holes and solitons like oscillons and cosmic strings. Here, we provide a review on isocurvature induced gravitational waves and its applications to dark matter and the primordial black hole dominated early universe.

Flat bands arise in periodic media when symmetries or fine-tuning result in perfect wavepacket localisation. Flat band localisation is fragile and exhibits remarkably sharp sensitivity to perturbations including interactions and disorder, leading to a variety of interesting quantum and classical phenomena. Originally a theoretical curiosity, advances in fabrication methods have allowed flat band physics to be observed down to the nanoscale. This article briefly reviews progress in the study of flat bands and disorder over the past decade and provides an outlook on where this exciting field is headed.

In this paper, molecular dynamics simulations have been employed to investigate the phonon thermal transport in bilayer polycrystalline graphene nanoribbon (pGNR/pGNR), compared with bilayer graphene nanoribbon (GNR/GNR) and pGNR/GNR heterostructure. The interfacial thermal resistance (ITR) of bilayer structures was also calculated using the heat dissipation method. The effects of interlayer interaction, grain size, and vacancy defects on ITR and in-plane phonon thermal conductivity of bilayer structures were investigated. It was found that the ITR as well as in-plane phonon thermal conductivity of pGNR/pGNR was less than that of pGNR/GNR and much less than that of GNR/GNR, for the same size. For the studied bilayer structures, both the ITR and in-plane phonon thermal conductivity decrease with increasing interlayer interactions. Moreover, ITR increases with increasing grain area size whereas decreases with increasing vacancy defects in pGNR-based bilayers. The introduction of pGNR interface roughness and vacancy defects results in an enhanced phonon coupling in pGNR-based bilayers compared to pure GNR/GNR bilayers. Presented simulation investigations will help to understand the interlayer thermal transport properties of polycrystalline graphene and provide essential guidance for experimentally regulating phonon thermal transport between layers of polycrystalline graphene.

The real atomic scale details of molecular junctions would be of much complexity and can yield a plethora of “counterintuitive” results. Here, we provide an overview of four unconventional intentional or unintentional transport phenomena in molecular junctions, in particular, unconventional tunneling length-dependent transport behavior, deviation from Kirchhoff’s superposition law, dual roles of imperfect engineering, and masked quantum interference. These abnormal phenomena are not engaged in a dead end. On the contrary, it offers plenty of research opportunities in molecular electronics.

A growing cohort of experimental linear photonic networks implementing Gaussian boson sampling (GBS) have now claimed quantum advantage. However, many open questions remain on how to effectively verify these experimental results, as scalable methods are needed that fully capture the rich array of quantum correlations generated by these photonic quantum computers. In this paper, we briefly review recent theoretical methods to simulate experimental GBS networks. We focus mostly on methods that use phase-space representations of quantum mechanics, as these methods are highly scalable and can be used to validate experimental outputs and claims of quantum advantage for a variety of input states, ranging from the ideal pure squeezed vacuum state to more realistic thermalized squeezed states. A brief overview of the theory of GBS, recent experiments, and other types of methods are also presented. Although this is not an exhaustive review, we aim to provide a brief introduction to phase-space methods applied to linear photonic networks to encourage further theoretical investigations.

Controllably fabricating low-dimensional systems and unraveling their exotic states at the atomic scale is a pivotal step for the construction of quantum functional materials with emergent states. Here, by utilizing the elaborated molecular beam epitaxy growth, we obtain various Fe_xSe_y phases beyond the single-layer FeSe/SrTiO₃ films. A synthetic strategy of lowering substrate temperature with superfluous Se annealing is implemented to achieve various stoichiometric FeSe-derived phases, ranging from 1:1 to 5:8. The phase transitions and electronic structure of these Fe_xSe_y phases are systematically characterized by atomic resolution scanning tunneling microscopy measurements. We observe the long-ranged antiferromagnetic order of the Fe₄Se₅ phase by spin-polarized signals with striped patterns, which is also verified by their magnetic response of phase shift between adjacent domains. The electronic doping effect in insulating Fe₄Se₅ and the kagome effect in metallic Fe₅Se₈ are also discussed, where the kagome lattice is a promising structure to manifest both spin frustration of d electrons in a quantum-spin-liquid phase and correlated topological states with flat-band physics. Our study provides promising opportunities for constructing artificial superstructures with tunable building blocks, which is helpful for understanding the emergent quantum states and their correlation with competing orders in the FeSe-based family.