Rb 3 SBr is proposed in this study as a lead-free anti-perovskite candidate for multifunctional solar-energy applications and is evaluated through an integrated first-principles and device-modeling approach. Its structural, mechanical, vibrational, electronic, and optical characteristics were examined using density functional theory (DFT), followed by photovoltaic and solar-driven hydrogen assessments using SCAPS-1D. The optimized cubic phase satisfies the examined elastic stability requirements, while the phonon spectrum contains no unstable modes, supporting its mechanical and dynamical viability. Also, negative formation energy suggests that Rb 3 SBr is thermodynamically stable. A Pugh ratio (B/G) of 1.73 places the compound slightly below the conventional ductile–brittle threshold of 1.75, suggesting a moderately brittle response close to the transition boundary. Electronic calculations identify a direct Γ-point transition, with energy gaps of 1.316 eV from PBE and 2.193 eV from HSE06. The material also exhibits pronounced visible–UV photon absorption, with α spanning approximately 0.5×10 5 −3.5×10 5 cm -1 , together with weak reflectance and favorable refractive behavior, indicating promising interaction with incident solar radiation. Device-level performance was examined using a lead-free Al/FTO/SnS 2 /Rb 3 SBr/CuO/Se heterojunction. With an Rb 3 SBr thickness of 0.6 µm, shallow acceptor concentration of 1×10 17 cm -3 , bulk defect concentration of 1×10 14 cm -3 , series resistance of 1 Ώ.cm 2 , and shunt resistance of 10 6 Ώ.cm 2 , the optimized SCAPS-1D model delivers J SC = 32.996 mA/cm 2 , FF = 83.68%, PCE = 26.24%, and V OC = 0.951 V. Beyond electricity generation, a conceptual series-connected photovoltaic configuration was evaluated for water splitting, predicting a solarto-hydrogen (STH) efficiency of 19.785%. Overall, the combination of favorable optoelectronic properties, calculated stability, and lead-free nature identifies Rb 3 SBr as a theoretically promising candidate for further investigation in photovoltaic, optoelectronic, and solar-driven hydrogen-production applications.
We investigate the existence, stability, and dynamical properties of composite gap solitons in Rashba spin-orbit-coupled Bose-Einstein condensates trapped in a bi-periodic optical potential. The system is modeled by two-component Gross-Pitaevskii equations incorporating cubic nonlinearities and Rashba-type spin-orbit coupling. We specifically focus on composite gap solitons formed by a fundamental soliton in the spin-down component and a dipole soliton in the spin-up component. The relationship between the total atom number and the chemical potential follows the anti-Vakhitov-Kolokolov criterion, establishing a necessary condition for stability. Through linear stability analysis and direct numerical simulations, we identify the stability domains of these state configurations. Notably, the inter-component (cross) interactions strongly dictate soliton stability: the repulsive cross-interaction yields significantly larger stability regions than the attractive, which often leads to narrower regions and soliton instability. These results provide a deeper insight into the behavior of multi-component gap solitons in spin-orbit-coupled systems with complex lattice geometries.
In this work, a comprehensive ab initio investigation of the structural stability, mechanical behaviour, optoelectronic response, and thermoelectric performance of FeZrCh (Ch = S, Se) half-Heusler (HH) alloys in cubic MgAgAs-type structure is carried out by the full-potential linearized augmented plane wave (FP-LAPW) method. The optimized lattice constants are found to be 5.69Å and 5.86Å for FeZrS and FeZrSe respectively. Both compounds are thermodynamically stable as confirmed by the negative formation energy. Mechanical analysis shows large values of Young's and bulk modulus, indicating strong structural stiffness and good resistance to thermal stress. Electronic structure analysis reveals that FeZrCh (Ch = S, Se) compounds exhibit semiconducting nature with indirect band gap of 0.890 eV and 0.630 eV for FeZrS and FeZrSe respectively. DOS results disclose strong Fe-d and chalcogen-p hybridization near the valence band, while Zr-d states dominate the conduction band, indicating favourable electronic transport characteristics. Optical analysis reveals pronounced absorption in the visible and near-ultraviolet regions, with absorption coefficients reaching the order of 10 4 cm -1 , indicating strong UV absorption capability in both compounds. The high static dielectric constants of 20.1 for FeZrS and 20.2 for FeZrSe, together with strong interband transition peaks around 2-3 eV and superior reflectivity in the higher-energy region, further highlight their suitability for optoelectronic and UV-absorbing applications. Thermoelectric analysis shows positive Seebeck coefficients of ∼232 μV/K for FeZrS and ∼248 μV/K for FeZrSe at room temperature, indicating dominant p-type carrier transport while the figure of merit (ZT) increases with temperature and reaches maximum values of 0.71 for FeZrS and 0.60 for FeZrSe at 1200 K, highlighting FeZrCh (Ch = S, Se) half-Heusler alloys as promising candidates for high-temperature thermoelectric and optoelectronic applications.
We present a comprehensive theoretical study of light drag effect in an optomechanical system incorporating Kerr non-linearity. The ability to dynamically control the speed and direction of light propagation is a well-established goal in optics, with applications ranging from all-optical routing to quantum information processing. We determine that an intensity-dependent refractive index, resulting from the Kerr limit [Formula: see text], provides exceptional control over the optomechanically induced transparency (OMIT) response. Our study shows that Kerr non-linearity changes the transparency condition of the OMIT to [Formula: see text], allowing for power-tunable control of the transparency frequency. Remarkably, we found that when the Kerr shift exceeds the critical value [Formula: see text], the dispersion slope reverses from normal to anomalous, resulting in a reversal of the light-dragging effect signal. This Kerr shift reversal enables complete optical switching between superluminal propagation (fast light) and subluminal propagation (slow light) exclusively by changing the power of the control laser. We systematically investigate the dependence of the light-drag on the probe detuning, laser detuning, mechanical damping rate, angular velocity and cavity decay rate. Our results show that the drag signal exhibits a linear dependence on the angular velocity, is maximal under the OMIT transparency condition and is significantly enhanced at low mechanical damping rates due to increased mechanical coherence and stronger optomechanical interaction. The drag signal enhancement factor is inversely proportional to the mechanical damping rate, demonstrating that high-quality mechanical resonators are essential for achieving strong optical drag effects.We demonstrate that the drag magnitude reaches [Formula: see text] [Formula: see text] for [Formula: see text] versus [Formula: see text] [Formula: see text] for [Formula: see text] when plotted versus probe detuning [Formula: see text] and laser detuning [Formula: see text], with linewidth broadening from FWHM [Formula: see text] to [Formula: see text] with increasing [Formula: see text]. Versus angular velocity [Formula: see text], the drag is antisymmetric [Formula: see text], zero at [Formula: see text], and saturates to [Formula: see text] versus [Formula: see text] for [Formula: see text], with low damping requiring smaller [Formula: see text] for saturation. Most importantly, Kerr non-linearity provides an all-optical knob to switch drag sign: below critical power [Formula: see text] OMIT dominates with positive drag up to [Formula: see text] [Formula: see text], at [Formula: see text] rad/s drag vanishes ([Formula: see text]) rad, and above critical power Kerr dominates giving negative drag down to [Formula: see text] [Formula: see text], with subsequent switching to [Formula: see text] [Formula: see text] at high [Formula: see text]. This demonstrates controllable fast-to-slow light switching and positive-to-negative rotary drag switching via pump intensity, crucial for non-reciprocal light propagation and rotational sensing. For experimentally achievable coefficients in silicon nitride cavities of [Formula: see text] radian/s and [Formula: see text], the required switching power is on the order of milliwatts, which is within current experimental possibilities. This work opens new avenues for fully optical control of light propagation in on-chip mechanical optoelectronic devices, with potential applications in quantum information processing, micro-sensing and optical buffering.
Low-dimensional and frustrated spin systems, especially large single crystals that are difficult to prepare synthetically, are often found in nature. This review compares three mineral families: green and black dioptase, Cu 6 [Si 6 O[Formula: see text]]⋅6H 2 O and Cu 6 Si 6 O[Formula: see text]; brochantite, Cu 4 SO 4 (OH) 6 ; and aegirine, NaFeSi 2 O 6 . These compounds span spin-[Formula: see text] chain physics and large-spin helical magnetism. The comparison focuses on how the hierarchy of intrachain, interchain, and anisotropic interactions determines magnetic dimensionality, ordered states, and spin dynamics. The dehydrated black dioptase shows how the removal of water from the structure changes the exchange hierarchy of Cu[Formula: see text] spin-[Formula: see text] spiral chains. Compared with green dioptase, it has stronger intrachain exchange, much weaker interchain coupling, reduced ordered moment, and continuum-like spinon excitations. Another spin-1/2 system, brochantite, shows a commensurate noncollinear magnetic order, while its excitations are incommensurate because of a uniform Dzyaloshinskii-Moriya interaction. High-field measurements reveal anisotropic transitions and short-range correlations beyond the minimal XXZ-chain model. In aegirine, a Fe[Formula: see text] spin-5/2 pyroxene, spin-wave measurements reveal a three-dimensional exchange network within a chain-like crystal structure. Magnetic field drives a helix-to-fan-to-collinear evolution controlled by anisotropic exchange. These minerals show how neutron scattering distinguishes structural from magnetic dimensionality and identifies the interactions that select ordered and field-induced states.
