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Metasurfaces offer a powerful platform for effective light manipulation, which is crucial for advanced optical technologies. While designs of polarization-independent structures have reduced the need for polarized illumination, they are often limited by either low Q factors or low resonance modulation. Here, we design and experimentally demonstrate a metasurface with polarization-independent quasi-bound state in the continuum (quasi-BIC), where the unit cell consists of four silicon squares arranged in a two-dimensional array and the resonance properties can be controlled by adjusting the edge length difference between different squares. Our metasurface experimentally achieves a Q factor of approximately 100 and a resonance modulation of around 50%. This work addresses a common limitation in previous designs, which either achieved high Q factors exceeding 200 with a resonance modulation of less than 10%, leading to challenging signal-to-noise ratio requirements, or achieved strong resonance modulation with Q factors of only around 10, limiting light confinement and fine-tuning capabilities. In contrast, our metasurface ensures that the polarization-independent signal is sharp and distinct within the system, reducing the demands on signal-to-noise ratio and improving robustness. Experiments show the consistent performance across different polarization angles. This work contributes to the development of versatile optical devices, enhancing the potential for the practical application of BIC-based designs in areas such as optical filtering and sensing.

In the strong-coupling regime, the interaction between light and matter reaches a hybridization state where the photonic and material components become inseparably linked. Using tailored states of light to break symmetries in such systems can underpin the development of novel non-equilibrium quantum materials. Chiral optical cavities offer a promising way for this, enabling either temporal or spatial symmetry-breaking, both of which are unachievable with conventional mirror cavities. For spatial symmetry-breaking a cavity needs to discriminate the handedness of circularly polarized light, a functionality that can only be achieved with metamaterials. Here, we suggest and demonstrate experimentally a chiral transition metal dichalcogenide (TMDC) metasurface with broken out-of-plane symmetry, allowing for a selective formation of self-hybridized exciton-polaritons with specific chirality. Our metasurface cavity maintains maximum chirality for oblique incidence up to 20{\deg}, significantly outperforming all previously known designs, thereby turning the angle of incidence from a constraint to a new degree of freedom for sub-nanometer precise control of resonance wavelengths. Moreover, we study the chiral strong-coupling regime in nonlinear experiments and show the polariton-driven nature of chiral third-harmonic generation. Our results demonstrate a clear pathway towards novel quantum material engineering with implications in a wide range of photonics research, such as superconductivity and valleytronics., Comment: 34 pages, 4 figures, and 12 supporting figures

Resonant dielectric planar structures can interact selectively with light of particular helicity thus providing an attractive platform for chiral flat optics. The absence of mirror-symmetry planes defines geometric chirality, and it remains the main condition for achieving strong circular dichroism. For planar optical structures such as photonic-crystal membranes and metasurfaces, breaking of out-of-plane mirror symmetry is especially challenging, as it requires to fabricate meta-atoms with a tilt, variable height, or vertically shifted positions. Although transparent substrates formally break out-of-plane mirror symmetries, their optical effect is typically subtle being rarely considered for enhancing optical chirality. Here we reveal that low-refractive-index substrates can induce up to maximum optical chirality in otherwise achiral metastructures so that the transparency to waves of one helicity is combined with resonant blocking of waves of the opposite helicity. This effect originates from engineering twisted photonic eigenstates of different parities. Our perturbation analysis developed in terms of the resonant-state expansion reveals how the eigenstate coupling induced by a substrate gives rise to a pair of chiral resonances of opposite handedness. Our general theory is confirmed by the specific examples of light transmission in the normal and oblique directions by a rotation-symmetric photonic-crystal membrane placed on different transparent substrates., Comment: 18 pages, 6 figures

We present an efficient method to perform overdamped Brownian dynamics simulations in external force fields and for particle interactions that include a hardcore part. The method applies to particle motion in one dimension, where it is possible to update particle positions by repositioning particle clusters as a whole. These clusters consist of several particles in contact. They form because particle collisions are treated as completely inelastic rather than elastic ones. Updating of cluster positions in time steps is carried out by cluster fragmentation and merging procedures. The presented method is particularly powerful at high collision rates in densely crowded systems, where collective movements of particle assemblies is governing the dynamics. As an application, we simulate the single-file diffusion of sticky hard spheres in a periodic potential., Comment: 15 pages, 7 figures

Microscopic particles flowing through narrow channels may accumulate near bifurcation points provoking flow reduction, clogging and ultimately chip breakage. Here we show that the full flow behavior of colloidal particles through a microfluidic Y-junction (i.e. a three way intersection) can be controlled by tuning the pair interactions and the degree of confinement. By combining experiments with numerical simulations, we investigate the dynamic states emerging when magnetizable colloids flow through a symmetric Y-junction such that a single particle can pass through both gates with the same probability. We show that clogging can be avoided by repulsive interactions and branching into the two channels can be steered as well by interactions: attractive particles are flowing through the same gate, while repulsive colloids alternate between the two gates. Even details of the particle assembly such as buckling at the exit gate are tunable by interactions and the channel geometry., Comment: 7 pages, 4 figures

In this paper, we introduce four comprehensive datasets for the Chuvash language, aiming to support and enhance linguistic research and technological development for this underrepresented language. These datasets include a monolingual dataset, a parallel dataset with Russian, a parallel dataset with English, and an audio dataset. Each dataset is meticulously curated to serve various applications such as machine translation, linguistic analysis, and speech recognition, providing valuable resources for scholars and developers working with the Chuvash language. Together, these datasets represent a significant step towards preserving and promoting the Chuvash language in the digital age.

Friction is central to the motion of active (self-propelled) objects, such as bacteria, animals or robots. While in a viscous fluid friction is typically described by Stokes' law, objects in contact with other solid bodies are often governed by more complex empirical friction laws. We study active dry particles subject to dry Coulomb friction force numerically and analytically. The interplay of friction and activity forces induces a rich behavior resulting in three distinct dynamical regimes. While for low activity levels, active Brownian motion is recovered, for large activity we observe a dynamical Stop & Go regime continuously switching from diffusion and accelerated motion. For further activity values, we observe a super-mobile dynamical regime characterized by a fully accelerated motion which is described by an anomalous scaling of the diffusion coefficient with the activity. These findings cannot be observed with Stokes viscous forces typical of active swimmers but are central in dry active objects., Comment: 6 pages, 4 figures plus supplemental material with 6 pages

Transport processes in crowded periodic structures are often mediated by cooperative movements of particles forming clusters. Recent theoretical and experimental studies of driven Brownian motion of hard spheres showed that cluster-mediated transport in one-dimensional periodic potentials can proceed in form of solitary waves. We here give a comprehensive description of these solitons. Fundamental for our analysis is a static presoliton state, which is formed by a periodic arrangement of basic stable clusters. Their size follows from a geometric principle of minimum free space. Adding one particle to the presoliton state gives rise to solitons. We derive the minimal number of particles needed for soliton formation, number of solitons at larger particle numbers, soliton velocities and soliton-mediated particle currents. Incomplete relaxations of the basic clusters are responsible for an effective repulsive soliton-soliton interaction seen in measurements. A dynamical phase transition is predicted to occur in current-density relations at low temperatures. Our results provide a theoretical basis for describing experiments on cluster-mediated particle transport in periodic potentials., Comment: 21 pages, 12 figures

We present a methodology for gathering a parallel corpus through crowdsourcing, which is more cost-effective than hiring professional translators, albeit at the expense of quality. Additionally, we have made available experimental parallel data collected for Chechen-Russian and Fula-English language pairs.

Chiral light sources realized in ultracompact device platforms are highly desirable for various applications. Among active media employed for thin-film emission devices, lead-halide perovskites have been extensively studied for photoluminescence due to their exceptional properties. However, up to date, there have been no demonstrations of chiral electroluminescence with a substantial degree of circular polarization (DCP), being critical for the development of practical devices. Here, we propose a new concept of chiral light sources based on a thin-film perovskite metacavity and experimentally demonstrate chiral electroluminescence with DCP approaching 0.38. We design a metacavity created by a metal and a dielectric metasurface supporting photonic eigenstates with close-to-maximum chiral response. Chiral cavity modes facilitate asymmetric electroluminescence of pairs of left and right circularly polarized waves propagating in the opposite oblique directions. The proposed ultracompact light sources are especially advantageous for many applications requiring chiral light beams of both helicities., Comment: 20 pages, 4 figures

Single-file diffusion refers to the Brownian motion in narrow channels where particles cannot pass each other. In such processes, the diffusion of a tagged particle is typically normal at short times and becomes subdiffusive at long times. For hard-sphere interparticle interaction, the time-dependent mean squared displacement of a tracer is well understood. Here we develop a scaling theory for adhesive particles. It provides a full description of the time-dependent diffusive behavior with a scaling function that depends on an effective strength of adhesive interaction. Particle clustering induced by the adhesive interaction slows down the diffusion at short times, while it enhances subdiffusion at long times. The enhancement effect can be quantified in measurements irrespective of how tagged particles are injected into the system. Combined effects of pore structure and particle adhesiveness should speed up translocation of molecules through narrow pores., Comment: 6 pages, 2 figures plus 4 pages, 3 figures in SM

The realization of lossless metasurfaces with true chirality crucially requires the fabrication of three-dimensional structures, constraining their feasibility for experiments and hampering practical implementations. Even though the three-dimensional assembly of metallic nanostructures has been demonstrated previously, the resulting plasmonic resonances suffer from high intrinsic and radiative losses. The concept of photonic bound states in the continuum (BICs) is instrumental for tailoring radiative losses in diverse geometries, especially when implemented using lossless dielectrics, but applications have so far been limited to planar and intrinsically achiral structures. Here, we introduce a novel nanofabrication approach to unlock the height of generally flat all-dielectric metasurfaces as an accessible parameter for efficient resonance and functionality control. In particular, we realize out-of-plane symmetry breaking in quasi-BIC metasurfaces and leverage this design degree of freedom to demonstrate, for the first time, an optical all-dielectric quasi-BIC metasurface with maximum intrinsic chirality that responds selectively to light of a particular circular polarization depending on the structural handedness. Our experimental results not only open a new paradigm for all-dielectric BICs and chiral nanophotonics but also promise advances in the realization of efficient generation of optical angular momentum, holographic metasurfaces, and parity-time symmetry-broken optical systems., Comment: Main text and supporting information, 35 pages, 3 Figures manuscript + 13 Supporting Figures

We propose a simulation method for Brownian dynamics of hard rods in one dimension for arbitrary continuous external force fields. It is an event-driven procedure based on the fragmentation and mergers of clusters formed by particles in contact. It allows one to treat particle interactions in addition to the hard-sphere exclusion as long as the corresponding interaction forces are continuous functions of the particle coordinates. We furthermore develop a treatment of sticky hard spheres as described by Baxter's contact interaction potential., Comment: 12 pages, 7 figures

Solitons are commonly known as waves that propagate without dispersion. Here we show that they can occur for driven overdamped Brownian dynamics of hard spheres in periodic potentials at high densities. The solitons manifest themselves as periodic sequences of different assemblies of particles moving in the limit of zero noise, where transport of single particles is not possible. They give rise to particle currents at even low temperature that appear in band-like structures around certain hard-sphere diameters. At high temperatures, the band-like structures are washed out by the noise, but the particle transport is still dominated by the solitons. All these predicted features should occur in a broad class of periodic systems and are amenable to experimental tests., Comment: 6 pages, 4 figures plus supplemental material with 7 pages and 1 figure; 5 ancillary movie files

In crowded systems, particle currents can be mediated by propagating collective excitations which are generated as rare events, are localized and have a finite lifetime. The theoretical description of such excitations is hampered by the problem of identifying complex many-particle transition states, calculation of their free energies, and the evaluation of propagation mechanisms and velocities. Here we show that these problems can be tackled for a highly jammed system of hard spheres in a periodic potential. We derive generation rates of collective excitations, their anomalously high velocities, explain the occurrence of an apparent jamming transition and its strong dependence on the system size. The particle currents follow a scaling behavior, where for small systems the current is proportional to the generation rate and for large systems given by the geometric mean of the generation rate and velocity. Our theoretical approach is widely applicable to dense nonequilibrium systems in confined geometries. It provides new perspectives for studying dynamics of collective excitations in experiments., Comment: 23 pages, 9 figures

Single-file transport in pore-like structures constitute an important topic for both theory and experiment. For hardcore interacting particles, a good understanding of the collective dynamics has been achieved recently. Here we study how softness in the particle interaction affects the emergent transport behavior. To this end, we investigate the driven Brownian motion of particles in a periodic potential. The particles interact via a repulsive softcore potential with a shape corresponding to a smoothed rectangular barrier. This shape allows us to elucidate effects of mutual particle penetration and particle crossing in a controlled manner. We find that even weak deviations from the hardcore case can have a strong impact on the particle current. Despite this fact, the knowledge about the transport in a corresponding hardcore system is shown to be useful to describe and interpret our findings for the softcore case. This is achieved by assigning a thermodynamic effective size to the particles based on the equilibrium density functional of hard spheres., Comment: 8 pages, 4 figures

We demonstrate that rotationally symmetric chiral metasurfaces can support arbitrarily sharp resonances with the maximum optical chirality determined by precise shaping of bound states in the continuum (BICs). Being uncoupled from one circular polarisation of light and resonantly coupled to its counterpart, a metasurface hosting the chiral BIC resonance exhibits a narrow peak in the circular dichroism spectrum. We propose a realization of such chiral BIC metasurfaces based on pairs of dielectric bars and validate the concept of maximum chirality by numerical simulations

We optimize optical performance of metasurfaces based on periodically corrugated silicon layers by adjusting the Fourier coefficients of their surface profile. For smooth corrugations, we demonstrate an excellent quantitative accuracy of semi-analytical approach based on the Rayleigh hypothesis. We employ the approach to design metasurfaces with anomalous refraction due to dominant first order diffraction. Unlike conventional Huygens' dielectric metasurfaces, corrugated silicon layers are capable of efficient anomalous refraction in grazing directions: we obtain corrugation shapes allowing to deflect 70-80% of the energy of normally incident green light into the range of 68{\deg}-85{\deg} of angles with respect to the normal., Comment: 8 pages 6 figures

We show theoretically and experimentally that a quantum cascade laser (QCL) in an external Fabry-Perot cavity (EC) can produce regular self-pulsations (SP) of the output intensity at frequencies ~75 GHz. We recognize that the propagation delay in EC provides QCL with a "memory" mechanism to preserve the regularity and coherence of the pulse train on the intervals significantly exceeding the sub-picosecond gain coherence and gain recovery times. These results may point to novel practical approaches for producing regular time-domain SPs and pulse trains in the Mid-IR QCLs. Otherwise, due to a multimode Risken-Nummedal-Graham-Haken (RNGH) instability, free-running FP QCLs exhibit SPs at Rabi flopping frequencies in the THz range, which in addition, reveal a quasi-periodic chaotic behavior if the cavity round trip time is a few picoseconds or more.