The Janus metastructure (JMS) is constructed in a special way so that the electromagnetic waves (EWs) propagate in the artificially constructed metastructure from different directions, which can show different electromagnetic characteristics and present a variety of functions at the same time. Its research is of great significance for breaking through the development bottleneck of traditional single-scale and single-function devices and can serve numerous novel application scenarios. This review discusses the design and research progress of JMS from three aspects: construction method, function realization, and application scenario. Finally, we discuss the key challenges currently facing the JMS and offer a vision for future research directions. We sincerely hope that this review will not only provide new insights into the development of JMS, which is a promising and dynamic hot research area but also promote research in this area from a more diverse and comprehensive perspective.

This study explores the behavior of laser-exposed photo-excited carriers, investigating the propagation of photoacoustic waves in the thermoelastic domain. It also delves into the theoretical generation of surface acoustic waves in semiconductors through photo-thermoelastic processes. The research considers the interaction between thermomechanical and acoustic waves in a nonlocal medium with temperature-dependent thermal conductivity. Unlike relying on electron–phonon or electron-hole thermalization processes, photoacoustic waves here result from thermoelastic stress induced by the laser-induced temperature increase. The investigation accounts for the optical, mechanical, and thermoelastic properties of nanoscale semiconductor materials. Predictions of photoacoustic signals are derived by solving a combined thermal diffusion issue and a thermoelastic problem, using Laplace and Fourier transforms in the mathematical model. Numerical solutions encompass various physical fields within the time domain using the inversion technique of Laplace and Fourier transforms, such as thermal, acoustic, mechanical, and carrier density diffusion. The study evaluates and compares the influences of thermal memory and thermal conductivity presenting visual representations.

Various researchers have attempted to design indium-free transparent conductive materials. This study first employed density functional theory combined with the Hubbard U parameter to predict the photoelectric properties of nonmetal (B, C, N, F, P, and S) and Nb co-doped anatase TiO2. The results indicate that Ti0.875Nb0.125O1.96875N0.03125, Ti0.9375Nb0.0625O1.96875F0.03125, Ti0.875Nb0.125O1.96875P0.03125 and Ti0.9375Nb0.0625O1.96875S0.03125 possess characteristics of n-type semiconductors with high transmittance, exceptional thermal stability and wide bandgap. Notably, Ti0.9375Nb0.0625O1.96875S0.03125 exhibits optimal electronic conductivity due to its lower effective mass and higher electron concentration. Then, we used the SCAPS-1D solar cell simulation software to simulate the macroscopic characteristics of the MASnI3-based perovskite solar cell with Ti0.9375Nb0.0625O1.96875S0.03125 transparent conductive oxide layer based on the microscopic properties computed at the density functional theory level. A maximum efficiency of 27.17 % is obtained by regulating the thickness, electron affinity, and defect density of Ti0.9375Nb0.0625O1.96875S0.03125 layer and the thickness of MASnI3 absorber layer. The findings highlight the tremendous potential of Ti0.9375Nb0.0625O1.96875S0.03125 as an indium-free transparent conductive oxide candidate material for photovoltaic applications.

We present a comparative study of the high-pressure behaviours of the nuclear waste immobilisation materials zirconolite-2 M, −4M, –3O, and −3T. The materials are studied under high-pressure conditions using synchrotron powder X-ray diffraction. For zirconolite-2 M we also performed density-functional theory calculations. A new triclinic crystal structure (space group P1¯), instead of the previously assigned monoclinic structure (space group C2/c) is proposed for zirconolite-2 M. We named the triclinic structure as zirconolite-2TR. We also found that zirconolite-2TR undergoes a phase transition at 14.7 GPa to a monoclinic structure described by space group C2/c, which is different than the high-pressure structure previously proposed in the literature. These results are discussed in comparison with previous studies on zirconolite-2 M and the related compound calzirtite. For the other three zirconolite structures (4 M, 3O, and 3 T) this is the first high-pressure study, and we find no evidence for pressure induced phase transitions in any of them. The linear compressibility of the studied compounds, as well as a room-temperature pressure–volume equation of state, are also presented and discussed.

The nonlinear optical susceptibilities are analyzed in their optical propagation length considering the incoherent-coherent contributions with the dependence on the relaxation times. In addition, some symmetry properties of the Four-Wave mixing (FWM) signal concerning the frequency detuning exchange are used in the study, without restricting ourselves to the maxima of population oscillations. We analyze the behaviors of these optical responses in a vibronic coupling scheme using a molecule model consisting of two coupled harmonic curves of electronic energies with displaced minima in position and nuclear energies. The solvent effect in our model is treated through the natural Bohr frequency shift to a time-dependent function, with explicit manifestations in its comparison as if the upper state were broadened. Our results for both FWM signal propagation and nonlinear optical susceptibilities are sensitive to the intramolecular coupling parameters, solvent stochasticity, and perturbation order for the treatment of the weak probe beam. The consideration of a second-order probe beam in FWM would not represent a significant contribution to the predicted results, since its percentage contribution is negligible within the model development framework; however, this contribution becomes important when increasing the ratio between longitudinal and transverse relaxation times.

The gas-sensing application potential of the TO8C monolayer for the target gases (NO, NO2, CO, CO2, NH3, CH4, H2O, and H2) was systematically investigated via DFT calculations. Only NO and NO2 adsorption can tune the electronic properties of the TO8C monolayer. Since the weak adsorption strength of NO and NO2 is unfavorable for the sensor device, E-field modulation was applied. Except as the enhancement of adsorption strength into desired ranges for NO and NO2, E-field modulation of −0.14 ∼ −0.21 V/Å for NO (0.08 ∼ 0.12 V/Å and −0.26 ∼ −0.29 V/Å for NO2) makes semiconducting transfer into conducting properties, indicating the sensitivity of the monolayer towards NO and NO2 gases was also effectively improved. However, the electronic properties of TO8C monolayer adsorbed with the other gases were hardly changed by the above-mentioned E-fields. When the applied E-fields were in −0.12 ∼ −0.17 V/Å (or −0.26 ∼ −0.29 V/Å), the conducting properties for NO (or NO2) adsorption were maintained in the existence of humidity, indicating that the determinate E-field is much favorable for the TO8C-based sensor to detect NO and NO2 gases without considering whether the humidity exists. Our findings reveal that the TO8C monolayers are compelling and feasible candidates for NO and NO2 resistance-type sensors at room temperature under the E-field modulation.

Seeking the available precision limit of unknown parameters is a significant task in quantum parameter estimation. One often resorts to the widely utilized quantum Cramér–Rao bound (QCRB) based on unbiased estimators to finish this task. Nevertheless, most actual estimators are usually biased in the limited number of trials. For this reason, we introduce two effective error bounds for biased estimators based on a unitary evolution process in the framework of the quantum optimal biased bound. Furthermore, we show their estimation performance by two specific examples of the unitary evolution process, including the phase encoding and the SU(2) interferometer process. Our findings will provide an useful guidance for finding the precision limit of unknown parameters.

We show coherent photons with spin and orbital angular momentum have symmetry of special unitary group of degree four, SU(4), both theoretically and experimentally. We show the degree of polarisation could be a measure to characterise the quantum coherency of a spin state, which was significantly affected by the partial trace out of orbital degree of freedom. By changing the amplitudes of the classically entangled state, we observed a crossover from quantum Heisenberg spin to classical Ising spin. We also demonstrated projections of coherent states, which recover the coherency of the spin state, while the SU(4) state is projected to be a simple product state of SU(2)×SU(2). Based on the developed platform, we have explored spin texture of coherent photons, and found a unique spin profile reminiscent of the Bengal cat upon wrapping to a three-dimensional sphere. We have controlled the phase between singlet and triplet states and found the spin texture rotated upon increasing the phase.

This work presents a method for achieving soliton transformation in a cold Rydberg atomic system to enable the realization of diverse optical potentials. Our investigation demonstrates that this system can generate various solitons, including Gaussian, elliptical, ring, and necklace structures, based on different optical lattice potentials. Additionally, stable transitions from Gaussian profile to three other profiles can be achieved either abruptly or gradually by adjusting the centers and modulation depths of potentials along the direction of light propagation. These findings highlight the versatility of this system for generating and manipulating solitons. The ability to control soliton transformation offers prospects for various applications, including all-optical switching, optical information processing, and other areas.

The present work focuses on developing nanocomposites for optoelectronics and energy storage devices leveraging the unique physicochemical features of bismuth (III) oxide (Bi2O3) using a polyvinyl pyrrolidone/polyvinyl alcohol matrix (PV(A/P)). Bi2O3 nanofillers (NF) and Bi2O3/PV(A/P) nanocomposite (NC) films were prepared by facile chemical solution approaches. The X-ray (XRD) data and a transmission electron image revealed that the NF exhibits a monoclinic phase, resembling slightly deformed agglomerated spheres. In the FTIR spectrum, different stretching vibrations of Bi-O-Bi bonds were found, along with their complexation and interaction with the reactive groups in the matrix. The SEM revealed a uniform distribution of Bi2O3 NF loading up to 1.5 wt% on the sample’s surface. Thermal analyses (TGA and DSC thermograms) were used to study the thermal stability, melting, and decomposition temperatures of the NC films. The dielectric features were studied under frequencies between 2 × 103 and 8 × 106 Hz and heating from 293 to 393 K. The dielectric constant and energy density were increased with Bi2O3 NF content. This implies that we can utilize the prepared NC for the fabrication of energy storage devices. The influences of the Bi2O3 NF doping level on the transmittance, band gap, Urbach energy, refractive index, conductivity, and other physical parameters were discussed. The modifications induced in the dielectric/optical parameters make the prepared NC films the best candidates for applications requiring a high refractive index, such as optical coatings and integrated photonic devices.