Narrow Resonance Research Articles

The tetraquark system in a chiral quark model* *Partially supported by the National Natural Science Foundation of China (12305093, 11535005, 11775118), the Natural Science Foundation of Zhejiang Province, China(LQ22A050004), the Ministerio Español de Ciencia e Innovación (PID2019-107844GB-C22, PID2022-140440NB-C22), the Junta de Andalucía under contract Nos. Operativo FEDER Andalucía (2014-2020 UHU-1264517, P18-FR-5057 and also PAIDI FQM-370)

The S-wave tetraquarks, with spin-parities , , and , in both isoscalar and isovector sectors, are systematically studied using a chiral quark model. The meson-meson, diquark-antidiquark, and K-type arrangements of quarks and all possible color wave functions are comprehensively considered. The four-body system is solved using the Gaussian expansion method, a highly efficient computational approach. Additonally, a complex-scaling formulation of the problem is established to disentangle bound, resonance, and scattering states. This theoretical framework has already been successfully applied in various tetra- and penta-quark systems. For the complete coupled channel and within the complex-range formulation, several narrow resonances of and systems are obtained, in each allowed -channel, within the energy regions of GeV and GeV, respectively. The predicted exotic states, which indicate a richer color structure when going towards multiquark systems beyond mesons and baryons, are expected to be confirmed in future high-energy particle and nuclear experiments.

Hot ion implantation to create dense NV center ensembles in diamond

Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.

Robust ultra-high-Q Fano resonance for topological corner and ring-cavity mode coupling in Kagome photonic systems

Corner and edge states in higher-order topological insulators provide new degrees of freedom for manipulating light propagation. Our research demonstrates that the topological waveguide coupled to the corner and edge states of the triangular cavity obtains a topological corner mode as narrow resonance and a topological ring-cavity mode as broad resonance, respectively. By adjusting the size of the dielectric column at the apex of the triangular cavity, the two modes can be coherently coupled at the same frequency position and obtain a high-Q Fano resonance. This Fano resonant has excellent robustness for unavoidable defects in the manufacturing process, paving the way for the design of high-performance lasers, switches, and other micro-nano integrated photonics devices.

Hidden-Charm Pentaquarks with Strangeness in a Chiral Quark Model

The LHCb collaboration has recently announced the discovery of two hidden-charm pentaquark states with strange quark content, Pcs(4338) and Pcs(4459); its analysis points towards having both hadrons’ isospins equal to zero and spin-parity quantum numbers 12− and 32−, respectively. Herein, we perform a systematical investigation of the qqscc¯(q=u,d) system by means of a chiral quark model, along with a highly accurate computational method, the Gaussian expansion approach combined with the complex scaling technique. baryon-meson configurations in both singlet- and hidden-color channels are considered. The Pcs(4338) and Pcs(4459) signals can be well identified as molecular bound states with dominant components ΛJ/ψ(60%) and ΞcD(23%) for the lowest-energy case and ΞcD∗(72%) for the highest-energy one. In addition, it seems that some narrow resonances can also be found in each allowed I(JP) channel in the energy region of 4.6–5.5 GeV, except for the 1(12−) channel where a shallow bound state with dominant Ξc∗D∗ structure is obtained at 4673 MeV with binding energy EB=−3 MeV. These exotic states are expected to be confirmed in future high-energy experiments.

A revisit to the plane problem for low-frequency acoustic scattering by an elastic cylindrical shell

The proposed revisit to a classical problem in fluid–structure interaction is due to an interest in the analysis of the narrow resonances corresponding to a low-frequency fluid-borne wave, inspired by modeling and design of metamaterials. In this case, numerical implementations would greatly benefit from preliminary asymptotic predictions. The normal incidence of an acoustic wave is studied for a circular cylindrical shell governed by plane strain equations in elasticity. A novel high-order asymptotic procedure is established considering for the first time all the peculiarities of the low-frequency behavior of a thin fluid-loaded cylinder. The obtained results are exposed in the form suggested by the Resonance Scattering Theory. It is shown that the pressure scattered by rigid cylinder is the best choice for a background component. Simple explicit formulae for resonant frequencies, amplitudes, and widths are presented. They support various important observations, including comparison between widths and the error of the asymptotic expansion for frequencies.

Reshaped three-body interactions and the observation of an Efimov state in the continuum

Efimov trimers are exotic three-body quantum states that emerge from the different types of three-body continua in the vicinity of two-atom Feshbach resonances. In particular, as the strength of the interaction is decreased to a critical point, an Efimov state merges into the atom-dimer threshold and eventually dissociates into an unbound atom-dimer pair. Here we explore the Efimov state in the vicinity of this critical point using coherent few-body spectroscopy in 7Li atoms using a narrow two-body Feshbach resonance. Contrary to the expectation, we find that the 7Li Efimov trimer does not immediately dissociate when passing the threshold, and survives as a metastable state embedded in the atom-dimer continuum. We identify this behavior with a universal phenomenon related to the emergence of a repulsive interaction in the atom-dimer channel which reshapes the three-body interactions in any system characterized by a narrow Feshbach resonance. Specifically, our results shed light on the nature of 7Li Efimov states and provide a path to understand various puzzling phenomena associated with them.

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Guidance of ultraviolet light down to 190 nm in a hollow-core optical fibre.

We report an anti-resonant hollow core fibre with ultraviolet transmission down to 190 nm, covering the entire UV-A, UV-B and much of the UV-C band. Guidance from 190 - 400 nm is achieved apart for a narrow high loss resonance band at 245 - 265 nm. The minimum attenuation is 0.13 dB/m at 235 nm and 0.16 dB/m at 325 nm. With an inscribed core diameter of ∼12 µm, the fibre's bend loss at 325 nm was 0.22 dB per turn for a bend radius of 3 cm at 325 nm.

Mass, Spectroscopy, and Two-Neutron Decay of ^{16}Be.

The structure and decay of the most neutron-rich beryllium isotope, ^{16}Be, has been investigated following proton knockout from a high-energy ^{17}B beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84(3) and 2.15(5)MeV above the two-neutron decay threshold and widths of 0.32(8) and 0.95(15)MeV, respectively. These were assigned to be the ground (J^{π}=0^{+}) and first excited (2^{+}) state, with E_{x}=1.31(6) MeV. The mass excess of ^{16}Be was thus deduced to be 56.93(13)MeV, some 0.5MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2^{+} level presents a far more diffuse neutron-neutron distribution.

Magnetic toroidal dipole resonance terahertz wave biosensor based on all-silicon metasurface

Optical sensing is crucial in many applications and has received widespread attention in recent years. Transmission spectroscopy with narrow linewidth resonances is indispensable for improving metasurface sensing performance. However, the narrower linewidth results in a smaller resonant modulation range, which seriously hinders the application of metasurfaces in sensing detection. We designed an all-silicon metasurface sensor. The structural layer of the metasurface works together with the substrate layer. Multiple magnetic ring dipoles are generated in the structural layer and multiple magnetic dipoles are generated in the substrate layer. The two work together to stimulate sharp Fano resonance, with a quality factor of up to 272.84. Based on the characteristics of metasurface, when applied to sensing and detection, the theoretical sensitivity can reach 59.64 GHz/RIU. Metasurface samples were successfully prepared using photolithography and dry etching. After characterizing the transmission spectrum of the prepared metasurface, the actual quality factor reached 76.8. At the same time, the metasurface sensor was used to detect bovine serum albumin (BSA) solutions of different concentrations. Based on the test results, it is calculated that the detection limit of the metasurface sensor for detecting BSA can reach 0.027 mg/mL, and the detection sensitivity can reach 9.7 GHz/(ng/mm2). The results of theoretical simulation and biological experiments show that the sensor has good sensing performance. This work is of great significance to the research of all-silicon metasurfaces and the application of metasurface sensors.

Experimental and Theoretical Studies on Ag Nanoparticles with Enhanced Plasmonic Response, Formed Within Al2O3 Thin Films Deposited by Magnetron Sputtering

AbstractReactive magnetron sputtering was employed to prepare nanocomposite thin films of Ag/Al2O3, on a glass substrate. The films are characterized by the formation of Ag nanoparticles embedded in the Al2O3 matrix, after thermal treatment at 600 °C, which are responsible for the appearance of an outstanding pronounced and narrow localized surface plasmon resonance (LSPR) band. Electron microscopy analysis also revealed the presence of larger Ag fractal aggregates at the film’s surface, responsible for a broad band absorption. Noteworthily, the LSPR band maximum remains at the same position (about 412 nm) for Ag concentrations ranging from 23 to 34 at.%, despite some discernible alterations in both LSPR band intensity and width. An optimized thin film is characterized by full transparency in non-resonant wavelengths due to suppression of Ag aggregates at the film’s surface, while maintaining the LSPR behavior. To better explain the plasmonic behavior of the Ag/Al2O3 films, discrete dipole approximation was used to determine the extinction, scattering, and absorption efficiencies of Ag spheres surrounded by an Al2O3 cap layer. This allowed to ascertain some nanostructural features of the films, pointing to the formation of Ag nanoparticles with average sizes in the order of 40 nm.

Experimental Study of Transverse Mode Suppression on Wideband Hetero Acoustic Layer Surface Acoustic Wave Resonator.

Transverse mode suppression is a great challenge for high-performance surface acoustic wave (SAW) resonators. Conventional methods work well on narrowband resonators, but their performances on wideband resonator have not been demonstrated. In this article, we give an in-depth study on the transverse mode suppression of wideband resonators using 11° YX-LiNbO3 (LN)/70 °Y90°X -quartz (Qz) hetero acoustic layer structure as a platform. Two groups of design, including new dummy electrode and zigzag shape apodization, are proposed. The measured results show that the shape of the dummy electrode is not the dominant factor to affect the transverse mode. The proposed zigzag shape apodization can effectively suppress the transverse, at the same time maintain the quality ( Q ) factor at the same level with the normal type. Additionally, stronger suppression ability can be realized with a tiny tradeoff of Q -factor.

Magneto-optical epitaxial bismuth-substituted yttrium iron garnet thin films on a diamagnetic substrate for low temperature applications

The uprising interest in the integration of the magneto-optical iron garnets into the field of quantum information processing imposes requirements for the damping parameter and optical properties at low temperatures. Typically, high quality iron garnet films are mostly grown epitaxially on the paramagnetic substrates that have rare-earth elements in its composition, which leads to an increase of their magnetic damping at temperatures below 100 K. Here, we epitaxially grew magneto-optical ferromagnetic garnet films on a diamagnetic yttrium scandium gallium garnet substrate to demonstrate narrow ferromagnetic resonance (FMR) linewidth at temperature range from 300 K to 4 K. The maximum Faraday angle measured at wavelength of 660 nm is ΘF = 0.34 ⋅103 deg/cm at 65 K. The FMR linewidth of the iron garnet film gets slightly larger as temperature decreases, but still remains at a level of 35 Oe at 4 GHz even at 4 K. The investigated iron garnet thin films grown on diamagnetic substrates can be successfully implemented in low-temperature technological applications that require low damping and high magneto-optical response.

Excitation of optical tamm state for photonic spin hall enhancement

This work presents a dielectric material-based optical Tamm state (OTS) excitation technique with modified dispersion characteristics for photonic spin hall effect (PSHE) enhancement. The dispersion analysis of the structure is carried out to validate OTS’s localization and corresponding PSHE generation for a given polarization at 632.8 nm incident wavelength. The exceptional points are optimized by considering thickness-dependent angular dispersion analysis. PSHE-based transverse displacement (PSHE-TD) is dependent on the defect layer thickness. The optimized structure provides 10.73 times lambda (or 6.78 upmum) PSHE-TD at an incidence angle of 41.86{}^{circ }. The PSHE-TD of the optimized structure is sufficiently high due to the much narrower resonance than the plasmonic-based structures. Further, the structure’s potential to function as a PSHE-TD-based optical sensor is assessed. The optimized structure shows an analytical average sensitivity of about 43,789 upmum/RIU showing its capability to detect the analytes with refractive index variations in the 10^{-4} range. The structure demonstrates a three-time sensitivity improvement compared to similar resonance designs. Considering only dielectric materials in the proposed structure and considerably enhanced PSHE-TD, the development of highly efficient PSHE-TD-assisted commercial structures is anticipated.

Search for toroids in excited nuclear material

Ground state nuclei usually have compact geometries. However, there have been theoretical predictions that excited nuclei can take on more extended shapes such as toroids or bubbles. There have been many attempts to identify signatures of such shapes in experimental data. One signature, both predicted by theory and reported in experimental data, is narrow resonances at high excitation energy in peripheral intermediate-energy heavy-ion collisions. This potential evidence for toroidal states was reported in the alpha particle disassembly of 28Si after collision with a 12C target at 35 MeV/nucleon. The prior work was limited by angular resolution and statistical uncertainties. The present work aims to measure the excitation energy distribution for these disassembly events with improved angular resolution and reduced statistical uncertainty using the Forward Array Using Silicon Technology (FAUST). FAUST is equipped with resistive dual-axis duo-lateral (DADL) position-sensitive silicon detectors capable of sub-millimeter position resolution. The measured excitation energy distributions of 7-α disassembly events showed no strong evidence for highly excited states at the cross section and widths suggested by previous experiment.

Narrow band absorption and sensing properties of single-walled carbon nanotubes at terahertz metasurface

Due to their excellent electrical and optical properties, carbon nanotubes have unique application prospects in the field of optoelectronics. In this work the vacuum self-assembly method is used to obtain an isotropic single-walled carbon nanotube film with a thickness of 2 μm by the dispersion of single-walled carbon nanotube powder through vacuum filtration; on the basis of extracting the dielectric parameters of the thin film in a range from 0.4 to 2.0 THz, a novel terahertz metasurface narrowband absorber based on single-walled carbon nanotube films is designed and prepared. This metasurface absorber is composed of square and I-shaped narrow slot resonators. The experimental and simulation results show that the proposed terahertz metasurface absorber exhibits four distinct resonance absorption peaks at 0.65, 0.85, 1.16, and 1.31 THz, respectively, achieving a perfect absorption of up to 90%. The absorption mechanism of this novel multi band terahertz metasurface is elucidated by using the theory of multiple reflection interference. By setting analytical layers with different refractive indices on the surface of metasurface device, the sensing performance of metasurface acting as refractive index sensor is studied in depth. The research results indicate that this new type of metasurface absorber has high sensitivity for refractive index sensing, providing new ideas and solutions for further developing carbon-based new terahertz metasurface absorbers.

Chalcophosphate metasurfaces with multipolar resonances and electro-optic tuning.

We computationally analyze the electro-optic response of metasurfaces consisting of interconnected nanoantennas with multipolar resonances using a chalcophosphate, Sn2P2S6, as the active material. Sn2P2S6 has large electro-optic coefficients and relatively low Curie temperature (<70 °C), allowing for strong changes in the refractive index of the material under moderate electric fields if the temperature can be finely controlled in proximity of the Curie point. Through numerical simulations, we show that metasurfaces designed with this nanostructured material demonstrate a significant shift of multipolar resonances upon biasing, despite moderate refractive-index values of the chalcophosphate and reduced mode localization due to this. The magnetic octupolar resonance of a dense array provides the strongest shift of spectral features upon changes in the refractive index, and we attribute it to the high mode localization of this higher-order multipole. We numerically demonstrate that narrow lattice resonances of collective nature do not provide an advantage in shifting the spectral features because of the nonlocal and delocalized nature of the modes, which are spread in the nanoantenna surrounding rather than confined inside nanoantennas. Both in-plane and out-of-plane biasing of the chalcophosphate crystals are similarly efficient with suitable electrode design, choice of electrode material, and crystal orientation within the nanoantennas. These designs exhibit optical properties similar to those of metasurfaces with isolated nanoantennas in the dense array.

A multichannel algebraic scattering approach to astrophysical reactions

The investigation of many astrophysical processes is dependent upon an understanding of nuclear reaction rates. However, nuclear capture reactions of astrophysical interest occur at extremely low energies, taking place at the Gamow energy within the stellar environment. Hence, they are hard to study experimentally due to Coulomb repulsion. They may also involve compound resonances stemming from a delicate interplay of many quantum states in the colliding bodies. The multi-channel algebraic scattering (MCAS) method is one that addresses both of these challenges; it has a history of successfully modelling narrow compound resonance structures, incorporating as many channels as are important for a given problem, but is also proven in recreating the lowenergy, non-resonant elastic scattering cross sections needed for these astrophysics problems. We provide an overview of MCAS’ techniques of modelling elastic scattering reactions, how these may be extended to capture reactions, and current work in this area.

Hybrid cavity-antenna architecture for strong and tunable sideband-selective molecular Raman scattering enhancement.

Plasmon resonances at the surface of metallic antennas allow for extreme enhancement of Raman scattering. Intrinsic to plasmonics, however, is that extreme field confinement lacks precise spectral control, which would hold great promise in shaping the optomechanical interaction between light and molecular vibrations. We demonstrate an experimental platform composed of a plasmonic nanocube-on-mirror antenna coupled to an open, tunable Fabry-Perot microcavity for selective addressing of individual vibrational lines of molecules with strong Raman scattering enhancement. Multiple narrow and intense optical resonances arising from the hybridization of the cavity modes and the plasmonic broad resonance are used to simultaneously enhance the laser pump and the local density of optical states, and are characterized using rigorous modal analysis. The versatile bottom-up fabrication approach permits quantitative comparison with the bare nanocube-on-mirror system, both theoretically and experimentally. This shows that the hybrid system allows for similar SERS enhancement ratios with narrow optical modes, paving the way for dynamical backaction effects in molecular optomechanics.

Quasi-bound states in the continuum in a metal nanograting metasurface for a high figure-of-merit refractive index sensor.

In this work, we investigate the bound states in the continuum (BICs) in a gold nanograting metal-insulator-metal metasurface structure at oblique angles of incidence. The nanograting metasurface consists of a gold nanograting patterned on a silicon dioxide dielectric film deposited on a thick gold film supported by a substrate. With rigorous full-wave finite difference time domain simulations, two bound states in the continuum are revealed upon transverse magnetic wave angular incidence. One BIC is formed by the interference between the surface plasmon polariton mode of the gold nanograting and the FP cavity mode. Another BIC mode is formed by the interference between the metal-dielectric hybrid structure guided mode resonance mode and the FP cavity mode. While true BIC modes cannot be observed, quasi-BIC modes are investigated at angles of incidence slightly off from the corresponding true BIC angles. It is shown that quasi-BIC modes can suppress radiation loss, resulting in narrow resonance spectral linewidths and high quality-factors. The quasi-BIC mode associated with the surface plasmon polariton mode is investigated for refractive index sensing. As a result, a high sensitivity refractive index sensor with a large figure-of-merit of 364 has been obtained.