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The decays of N ∗ and ∆ ∗ resonances into Nρ , ∆ π , and N $f$ 0 (500), and final states are investigated in a coupled-channel analysis of data from pion- and photoinduced reactions. Improvements in the fit quality are observed upon the inclusion of additional resonance contributions. Branching ratios for the intermediate isobars ∆(1232) π , Nρ , and N $f$ 0 (500) are reported.
In doped transition metal dichalcogenides, optically created excitons (bound electron-hole pairs) can strongly interact with a Fermi sea of electrons to form Fermi polaron quasiparticles. When there are two distinct Fermi seas, as is the case in WSe 2 , there are two flavors of lowest-energy (attractive) polarons—singlet and triplet—where the exciton is coupled to the Fermi sea in the same or opposite valley, respectively. Using two-dimensional coherent electronic spectroscopy, we analyze how their quantum decoherence evolves with doping density and determine the condition under which stable Fermi polarons form. Because of the large oscillator strength associated with these resonances, intrinsic quantum dynamics of polarons as well as valley coherence between coupled singlet- and triplet polarons occur on subpicosecond timescales. Surprisingly, we find that a dark-to-bright state conversion process leads to a particularly long-lived singlet polaron valley polarization, persisting up to 200–800 ps. Valley coherence between the singlet- and triplet polaron is correlated with their energy fluctuations. In conclusion, our finding provides valuable guidance for the electrical and optical control of spin and valley indexes in atomically thin semiconductors.
We consider the dynamical properties of a gapped quantum spin system coupled to the electric field of a laser, which drives the resonant excitation of specific phonon modes that modulate the magnetic interactions. Here, we deduce the quantum master equations governing the time-evolution of both the lattice and spin sectors, by developing a Lindblad formalism with bath operators providing an explicit description of their respective phonon-mediated damping terms. We investigate the nonequilibrium steady states (NESS) of the spin system established by a continuous driving, delineating parameter regimes in driving frequency, damping, and spin-phonon coupling for the establishment of physically meaningful NESS and their related nontrivial properties. Focusing on the regime of generic weak spin-phonon coupling, we characterize the NESS by their frequency and wave-vector content, explore their transient and relaxation behavior, and discuss the energy flow, the system temperature, and the critical role of the type of bath adopted. Our study lays a foundation for the quantitative modeling of experiments currently being designed to control coherent many-body spin states in quantum magnetic materials.
We study the resonant enhancement of linear and nonlinear chiroptical effects in planar silicon metasurfaces with an in-plane asymmetry supporting multipolar Mie resonances and quasi-bound states in the continuum (quasi-BICs). We demonstrate theoretically and observe in experiment the pronounced linear circular dichroism at the quasi-BIC resonances originating from the interaction of modes with the substrate. We further find that both local field enhancement and third-harmonic signal are large for Mie resonances and some quasi-BIC modes due to the critical coupling. We demonstrate experimentally a strong nonlinear chiroptical response associated with high efficiency of the third-harmonic generation and large nonlinear circular dichroism varying from +0.918 ± 0.049 to –0.771 ± 0.004 for the samples with different asymmetries. We reveal the nonreciprocal nature of nonlinear chirality governed by the microscopic symmetry of nonlinearities and macroscopic symmetries of the meta-atom and metasurface lattice. Here, we believe our results suggest a general strategy for engineering nonlinear chiroptical response in dielectric resonant metasurfaces.
We investigate the structural and electronic origin of antiferromagnetic (AFM) coupling in the yttrium iron garnet (YIG) and permalloy (Ni 80 Fe 20 , Py) bilayer system at the atomic level. Ferromagnetic resonance (FMR) spectra reveal unique hybrid modes in samples prepared with surface ion milling, indicative of antiferromagnetic exchange coupling at the YIG/Py interface. Using atomic resolution scanning transmission electron microscopy (STEM), we found that AFM coupling appears at the YIG/Py interface of the tetrahedral YIG surface formed with ion milling. Here, the STEM measurements suggest that the interfacial AFM coupling is predominantly driven by an oxygen-mediated superexchange coupling mechanism, which is confirmed by the density-functional theory (DFT) calculations to be energetically favorable. Thus, the combined experimental and theoretical results reveal the critical role of interfacial atomic structure in determining the type of magnetic coupling in a YIG/ferromagnet heterostructure, and prove that the interfacial structure can be experimentally tuned by surface ion milling.
We study the radiative properties—the Lamb shift, Purcell decay rate, and spontaneous emission dynamics—of an artificial atom coupled to a long, multimode cavity formed by an array of Josephson junctions. Introducing a tunable coupling element between the atom and the array, we demonstrate that such a system can exhibit a crossover from a perturbative to a nonperturbative regime of light-matter interaction as one strengthens the coupling between the atom and the Josephson-junction array. As a consequence, the concept of spontaneous emission as the occupation of the local atomic site being governed by a single complex-valued exponent breaks down. This breakdown, we show, can be interpreted in terms of formation of hybrid atom-resonator modes with radiative losses that are nontrivially related to the effective coupling between individual modes. We develop a singular function expansion approach for the description of the open quantum system dynamics in such a multimode nonperturbative regime. This modal framework generalizes the normal-mode description of quantum fields in a finite volume, incorporating exact radiative losses and incident quantum noise at the delimiting surface. Our results are pertinent to recent experiments with Josephson atoms coupled to high-impedance Josephson-junction arrays.
The OECD NEA CSNI WGAMA CFD Task Group ran a benchmark in 2020 and 2021 to assess the predictive capabilities of coupled fluid structure interaction (FSI) CFD analysis methods. This paper presents the predictions made for the open phase of the benchmark using URANS and LES turbulence modelling approaches, and a comparison of the results to the experimental data. The benchmark comprised a channel containing two inline cylinders in cross-flow. The cylinders were fixed at one end, free at the other, and had measured resonant frequencies and damping properties. The URANS modelling used ANSYS Fluent 2-way coupled to ANSYS Mechanical. The LES modelling used Nek5000, 1-way coupled to Diablo. Comparisons with cross-channel velocity profiles are presented, both for the mean flow and its RMS. Comparisons are also made to the frequency spectra for point measurements of fluid velocity and pressure, and for the accelerations of the free end of each cylinder. URANS predicts the average velocity profiles relatively well, and is able to predict the velocity and acceleration spectra at the shedding frequency. However, the frequency content at the 4th harmonic of the shedding frequency is low in the URANS flow fields, and so does not excite accelerations at the resonant frequency of the cylinders. LES makes better predictions of the average profiles, and the velocity spectra agree well at both the shedding frequency and at higher frequencies. In conclusion, the 1-way coupled LES results show good agreement for acceleration spectra.
Excitons are vital in the photophysics of materials, especially in low-dimensional systems. The conceptual and quantitative understanding of excitonic effects in nonlinear optical (NLO) processes is more challenging compared to linear ones. Here, we present an ab initio approach to second-order NLO responses, incorporating excitonic effects, that employs an exciton-state coupling formalism and allows for a detailed analysis of the role of individual excitonic states. Taking monolayer h-BN and MoS 2 as two prototype 2D materials, we calculate their second harmonic generation (SHG) susceptibility and shift current conductivity tensor. We find strong excitonic enhancement in the NLO responses requires that the resonant excitons are not only optically bright themselves but also able to couple strongly to other bright excitons. Our results explain the occurrence of two strong peaks in the SHG of monolayer h-BN and why the A and B excitons of MoS 2 unexpectedly exhibit minimal excitonic enhancement in both SHG and shift current generation.
We present a comprehensive exploration of loop-gap resonators for electron spin resonance (ESR) studies, enabling investigations into the hybridization of solid-state magnetic materials with microwave polariton modes. The experimental setup, implemented in a Physical Property Measurement System by Quantum Design, allows for measurements of ESR spectra at temperatures as low as 2 Kelvin. The versatility of continuous wave ESR spectroscopy is demonstrated through experiments on CuSO 4 •5H 2 O and MgCr 2 O 4 , showcasing the g-tensor and magnetic susceptibilities of these materials. The study delves into the challenges of fitting spectra under strong hybridization conditions and underscores the significance of proper calibration and stabilization. The detailed guide provided serves as a valuable resource for laboratories interested in exploring hybrid quantum systems through microwave resonators.
We report fully suppressing edge-localized modes (ELMs), e.g., with resonant magnetic perturbations (RMPs), is essential to reach and sustain high-performance steady-state H-mode plasmas because large ELMs can significantly reduce the lifetime of divertor components in future tokamak reactors. RMP-driven ELM suppression in KSTAR has been modeled by coupling the neoclassical transport code PENTRC to the nonlinear 3D MHD code JOREK. We have found that the radial transport from the combined effects of the kink-peeling, tearing response, and neoclassical toroidal viscosity can explain the pedestal degradation observed in experiments. In addition, it has been found that the RMP response can increase the inter-ELM heat flux on the lower outer divertor by redistributing the heat transport between the divertor plates. In addition to the degraded pedestal, ELM suppression is also attributable to the RMP-induced mode interactions. While the linear stability of peeling-ballooning mode (PBMs) improves owing to the degraded pedestal, the PBM and RMP interaction increases the spectral transfer between edge harmonics, preventing catastrophic growth and the crash of unstable modes. Here, it turns out that the magnetic islands near the pedestal top can play a vital role in mediating the mode interactions.
The utility of a quantum computer is highly dependent on the ability to reliably perform accurate quantum logic operations. For finding optimal control solutions, it is of particular interest to explore model-free approaches, since their quality is not constrained by the limited accuracy of theoretical models for the quantum processor—in contrast to many established gate implementation strategies. In this work, we utilize a continuous control reinforcement learning algorithm to design entangling two-qubit gates for superconducting qubits; specifically, our agent constructs cross-resonance and CNOT gates without any prior information about the physical system. Using a simulated environment of fixed-frequency fixed-coupling transmon qubits, we demonstrate the capability to generate novel pulse sequences that outperform the standard cross-resonance gates in both fidelity and gate duration, while maintaining a comparable susceptibility to stochastic unitary noise. We further showcase an augmentation in training and input information that allows our agent to adapt its pulse design abilities to drifting hardware characteristics, importantly, with little to no additional optimization. Our results exhibit clearly the advantages of unbiased adaptive-feedback learning-based optimization methods for transmon gate design.
Approaches for predicting low-lying resonances, uniformly treating bound, and resonant levels have been a long-standing goal in nuclear theory. Accordingly, we explored the viability of the complex momentum representation (CMR) approach coupled with new potentials. We focus on predicting the energy of the low-lying 2p 3/2 resonance in 17 O, which is critical for s-process nucleosynthesis and missing in previous theoretical research. Here, using a Woods-Saxon potential based on the Koning-Delaroche optical model and constrained by the experimental one-neutron separation energy, we successfully predicted the resonant energy of this level for the first time. Our predictions of the bound levels and 1d 3/2 resonance agree well with the measurement results. Additionally, we utilize this approach to study the near-threshold resonances that play a role when forming a two-neutron halo in 29,31 F. We found that the CMR-based predictions of the bound-level energies and unbound 1f 7/2 level agree well with the results obtained using the scattering phase shift method. Subsequently, we successfully found a solution for the 2p 3/2 resonance with energy just above the threshold, which is decisive for halo formation.
Reaction of [UO 2 Cl 2 (THF) 2 ] 2 with in situ generated LiFmes (FmesH = 1,3,5-(CF 3 ) 3 C 6 H 3 ) in Et 2 O resulted in the formation of the uranyl aryl complexes [Li(THF) 3 ][UO 2 (Fmes) 3 ] ([Li(THF) 3 ][1]) and [Li(Et 2 O) 3 (THF)][UO 2 (Fmes) 3 ] ([Li(Et 2 O) 3 (THF)][1]) in good to moderate yields after crystallization from hexanes and Et 2 O, respectively. Both complexes were characterized by X-ray crystallography and NMR spectroscopy. DFT calculations reveal that the C ispo resonance in [1] – exhibits a deshielding of 51 ppm from spin–orbit coupling effects originating at uranium, which indicates an appreciable covalency in the U–C bonding interaction.
The first measurements of femtoscopic correlations with the particle pair combinations π ± $K$$^{0}_{S}$ in pp collisions at $\sqrt{s}$ = 13 TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive $K$$^{*}_{0}$(700) particle that has been considered a tetraquark candidate for over forty years. Source and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction in the π ± $K$$^{0}_{S}$ system is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, The extracted mass and Breit–Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the $K$$^{*}_{0}$ (700). The small value and increase of the correlation strength with increasing source size support the hypothesis that the $K$$^{*}_{0}$(700) is a four-quark state, i.e. a tetraquark state of the form (q 1 , $\bar{q}$ 2 , q 3 , $\bar{q}$ 3 ) in which q 1 , q 2 and q 3 indicate the flavor of the valence quarks of the π and $K$$^{0}_{S}$. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the $K$$^{*}_{0}$(700) resonance.
Advanced explosive formulations and methods of production require rapid characterization for both processes and materials. Here, we present results for ultrasound characterization of a plastic bonded explosive (PBX) formulation as a function of binder weight percent and pressing density using through-transmission sound speed measurements. The explosive in this study was composed of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) combined with the fluoropolymer binder Kynar Ultraflex B. Binder content ranged from 2.6 wt.% to 11.5 wt.% with associated explosive formulation densities from 1.69 g/cc to 1.89 g/cc. We find linear and nonlinear changes in longitudinal and shear sound speeds, peak frequencies, and measured elastic properties for the different PBX formulations. These measured changes can differentiate the tested formulations, highlighting the potential for ultrasound as a nondestructive characterization method for newly-formulated PBXs. We also demonstrate through-transmission measurements using different coupling media and present results from an ultrasound technique called resonant ultrasound spectroscopy (RUS). Both transmission and RUS approaches may allow for rapid and even automated characterization of PBX components suitable for high-throughput manufacturing operations.
This article deals with research, development and future directions of magnetoelectric composites for practical devices applications. In the past 20 years there has been a surge of research in the area of multiferroics (MF) and magnetoelectrics (ME) due to their potential to replace existing technologies based only on ferroelectric or ferromagnetic materials. Some of the magnetoelectric composites show exceptionally high potential in the area of magnetic field sensors, however, work remains before commercialization can be realized. The cross coupling among various ferroic parameters in magnetoelectric composites is several orders higher than single phase magetoelectrics, which make its favorable for low detection (nT or pT) magnetic field sensors. Advances in both layered structures or controlled three-dimensional matrix composites for applications as magnetoelectric nonvolatile memory elements are both required. Robust cross-coupling among various parameters with more than four logic states and its compatibility with complementary-symmetry metal–oxide–semiconductor (CMOS) technology are the main requirements for heterostructure magnetoelectric thin films. The major hurdles in the area of magnetoelectric nonvolatile memory elements are poor interfacial properties and weak magnetoelectric coupling for high density fast read and write processes. Another potential area is strained coupled magneto-electric composites where magnetostriction mediated dimensional change in the magnetic layer effectively modulate the change in the dimension of piezoelectric layers via piezostriction, which leads to a strong ME coupling where their coupling magnitude is sufficient for magnetic field sensors. Energy harvesters based on magnetoelectric composites are also intriguing concepts to capture various types of waste energy, in the form mechanical vibration, pressure, wind energy, hydrothermal and waste temperature.
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