Abstract We propose a rotation-controlled nonlinear orbital-angular-momentum (OAM) filter based on photonic-band-gap-assisted four-wave mixing (PBG-FWM) in rubidium vapor. The model follows the field convention of PBG-FWM experiments: an OAM probe field $E_1$ is Bragg-reflected through the nonlinear polarization produced with two counterpropagating Gaussian coupling fields $E_3$ and $E_3'$, while the generated field is denoted by $E_F$. The coupling pair forms a standing-wave Rabi frequency $|G_{3s}|^2=|G_3|^2+|G_3'|^2+2G_3G_3'\cos(2k_3z)$, which creates the longitudinal PBG modulation and enters the resonant denominator of the third-order susceptibility. Rotation adds an OAM-dependent rotational Doppler shift to the probe and generated FWM modes. In a slow-light PBG-FWM medium this shift is converted into a longitudinal phase-matching perturbation, giving $\eta_m(\Omega)=\eta_0{\rm sinc}^2[\Delta k_{\rm rot}^{(m)}L/2]$ in the phase-matching-dominated limit. Rotation can also perturb $\chi^{(3)}$ through Doppler-shifted detunings, producing envelope and asymmetry corrections. The theory predicts OAM-dependent FWM quenching, the readable petal rotation, and a rotationally tunable OAM cutoff. The results provide a design route for rotation-sensitive structured-light processing in atomic nonlinear media.
Abstract We report in this paper the mechanism of evolution of chaotic hysteresis and its control in a second-order non-autonomous nonlinear circuit subjected to two external forces with incommensurate frequencies and a DC offset voltage. Chaotic hysteresis is evidenced together with the observation of strange non-chaos in the dynamics of the system. It has been observed that the existence of multistability in the dynamical behavior of the system becomes quintessential for the evolution of the initial condition-dependent chaotic hysteresis in these systems. A complete study carried out by numerical, analytical and experimental investigations on the evolution of chaotic hysteresis in the system is reported. The stability of the attractors in the different hysteresis paths is studied through an analysis of the potential-well function of the system and on the displacement of the equilibrium points in the phase space with the DC offset factor. The multistability nature of the attractors obtained at the hopping points of the chaotic hysteresis paths is validated through studies on the basin of attraction of these attractors. Further, the emergence and control of chaotic hysteresis and the different types of synchronization behavior accompanying hysteresis in one-way coupled systems under different parameter conditions are reported.
Abstract This work theoretically investigates a one-dimensional topological photonic crystal sensor incorporating dual porous silicon layers for enhanced organic analyte detection, with emphasis on acetone monitoring in wastewater. The structure comprises two centrosymmetric photonic crystals separated by a porous silicon cap layer, plus an identical porous layer at the far end, supporting topological interface states within the common photonic bandgap. The sensing performance of the structure is analyzed in terms of physical parameters and porosity of both the intermediate and surface cap layers. A key advantage of introducing porosity is the increased surface-to-volume ratio, which enhances the interaction between the analyte and the optical field within the structure, leading to improved sensitivity and limit of detection. Using the transfer matrix method, the influence of cap layer thickness and porosity on sensitivity, quality factor (Q-factor), figure of merit (FoM), and limit of detection (LoD) is examined. The sensing performance is then evaluated as a function of the analyte refractive index over the range of 1.33 to 1.44. Sensitivity and LoD decrease with increasing refractive index, while FoM increases, with the most significant variations occurring in the 1.33–1.34 range. By appropriately selecting the structural parameters for both layers, the optimized sensor is applied to detect various alcohol concentrations, showing favorable performance, particularly in terms of limit of detection. Compared to similar structures, the proposed design achieves an order-of-magnitude improvement through structural optimization, indicating significant potential for environmental and biomedical diagnostics.
Abstract The recent discovery of high-temperature superconductivity in nickelates under high pressure has garnered widespread attention. Experimental measurements presents the direct observation of a spin-density wave state, indicating the long-range magnetic order evident. However, ascertaining the presence of long-range magnetic order and identifying the magnetic ground state in high-quality single crystal remains a challenge in experiments. Theoretical calculations yield divergent predictions of the ground-state magnetic order, stemming from limitations in exchange-correlation functionals when addressing the strong electron correlations inherent to these systems. Here, we employ the strongly constrained and appropriately normed (SCAN) meta-GGA functional to investigate the magnetic ground state of La 3 Ni 2 O 7 . This approach circumvents the need for empirically tuned Hubbard U parameters required in conventional DFT+U calculations, while also eliminating metastability issue that compromise computational reliability. Our results demonstrate that the A-type antiferromagnetic configuration constitutes the magnetic ground state in the Amam phase, whereas a double spin stripe (DSS) order without spinless configuration emerges as the favored ground state in the Fmmm phase. We further show that the d x 2 -y 2 and d z 2 orbitals, which lie in close proximity to the Fermi level, mediate enhanced superexchange interactions under increasing pressure — a key factor driving the emergence of high-temperature superconductivity. Moreover, interbilayer magnetic couplings substantially modulate the ground-state enthalpy, generate inequivalent Ni sites, and stabilize the experimentally observed bimodal‑moment DSS state. They should therefore be considered an important ingredient for understanding superconductivity in nickelates. Collectively, our work demonstrates the applicability of the parameter‑free SCAN meta‑GGA functional for investigating strongly correlated nickelates with nearly fully occupied d orbitals.
Abstract This paper examines the Riemann problem for one-dimensional models of arterial and venous blood flow that include passive scalar transport and account for vessel-specific tube laws. The elementary wave curves of the Riemann problem are derived using the method of characteristics and projected into the relevant phase plane to simplify the analysis. Within the phase-plane framework, we establish a necessary and sufficient criterion for the emergence of vacuum states in arterial flow, while such phenomena do not occur in venous flow. Furthermore, for non-vacuum initial data, we prove the existence and uniqueness of the Riemann solution. Moreover, the interactions of shock waves of both the same and different families are studied in detail, and the resulting wave configurations are classified.
