Boosting H2O2 activation to hydroxyl radicals via electronic modulation of asymmetric Fe-O3Cl1-C catalysts for water decontamination.

Fluids, characterized by broken time-reversal and parity symmetries, exhibit odd transport phenomena where longitudinal drivings can induce transverse fluxes. Recently, a mesoscale model called chiral stochastic rotation dynamics (CSRD) has been developed to simulate odd fluids with high computational efficiency. In this work, we verify the Green-Kubo relations for both normal and odd transport coefficients in this model, confirming that this model correctly captures the underlying statistical relationship between macroscopic transport and microscopic fluctuations in odd fluids. This work solidifies the physical foundation of the CSRD model, paving the way for its application in studying the statistical physics and nonequilibrium behavior of odd fluids.

• Extension of SAFE-PML to simulate infinite 3D porous media; • Analysis of wave modes and dispersion in fluid-filled wells within 3D porous solids; • Dispersion and mode behavior studied under different physical conditions and parameters; • Application to sonic logging and multiphysics scenarios; • Symmetry breaking and coupling of propagating modes induced by an eccentric logging tool; Fast and accurate numeric simulation of wave propagation in sonic well logging is of extreme practical interest. We present the extension of the Semi-Analytical Finite Element (SAFE) method combined with Perfectly Matched Layers (PML) to model wave propagation in fluid-filled boreholes surrounded by infinite porous formations. The borehole system is treated as a multilayered and multiphysics 3D waveguide. Biot’s poroelastic theory is incorporated using the ( u s , w ) formulation to accurately capture fluid–porous solid interactions. The SAFE-PML approach enables the simulation of both trapped and leaky modes under open and closed porous boundary conditions. Validation is performed using analytical solutions, demonstrating excellent agreement. A sonic logging tool is also explicitly included in the model, allowing the analysis of its eccentricity on the dispersion characteristics. In particular, we show how the tool eccentricity breaks the radial symmetry of the trapped modes (like the Stoneley), lowering their phase velocity and breaking higher-order modes degeneracy. Our numerical results demonstrate the method’s ability to capture key effects relevant to borehole acoustics, especially those associated with symmetry breaking, which can be challenging to treat analytically. It also demonstrates that the SAFE-PML method can serve as an efficient and accurate modeling framework for realistic borehole acoustic scenarios involving poroelastic formations.

The broken inversion symmetry at interfaces of complex oxides gives rise to emergent phenomena, such as ferromagnetism and Rashba spin-orbit coupling (SOC) which influence the electronic structure by entangling spin and momentum. While the interplay between Rashba SOC and ferromagnetism is theoretically intriguing, its experimental manifestations remain largely unexplored. Here we demonstrate a ferromagnetic Rashba two-dimensional electron gas at a SrTiO3-based interface in which the anomalous Hall effect (AHE) and nonlinear transport can be tuned electrostatically. The AHE varies in amplitude but also reverses sign with gate voltage due to the reversal of the net Berry curvature, providing a distinct form of magnetoelectric switching. In addition, we observe spontaneous nonreciprocal transport at zero magnetic field whose polarity is governed by the remanent magnetization and is strongly gate-tunable. These results establish oxide-based ferromagnetic Rashba 2DEGs as a platform to engineer Berry-curvature landscapes and explore gate-tunable spintronic functionalities driven by band topology.

We computationally investigate how environmental sensitivity of active matter interacts with soft confinement to shape collective dynamics. In our model, the active constituents are represented as self-propelled particles (SPPs), implemented as nematic, disjoint ring polymers whose direction of motion can reverse without tumbling, with a directional persistence controlled by the driving force, FD, and a persistence time scale, τm. Coarse-grained molecular dynamics simulations of these reversal-capable SPPs confined within a deformable two-dimensional enclosure reveal that the collective dynamics arise from a three-way feedback between active stresses, boundary elasticity, and particle-level memory. With increasing FD, this stress-boundary-memory feedback generates a sequence of collective dynamical regimes. At low FD, SPP motion is dominated by thermal fluctuations and activity plays a negligible role. At intermediate FD, coherent vortical motion emerges with intermittent, noise-driven reversals. The frequency of reversals is modulated by boundary elasticity and τm, and their occurrence coincides with transient coherent polar motion. With further increase in FD, reversals are suppressed, yielding sustained unidirectional vortical motion in which the enclosure exhibits diffusive propulsion with a diffusivity that varies non-monotonically with FD. At sufficiently high FD, the system transitions to a polar state characterized by strong nematic ordering of the SPPs, symmetry breaking of the enclosure shape, and persistent polar collective motion. In this regime, the SPPs accumulate at the leading edge of the enclosure, deforming it into an anisotropic shape and driving sustained ballistic propulsion of the enclosure with a slowly drifting direction. These results demonstrate how environmental sensitivity and soft confinement jointly regulate emergent collective states of confined active matter and identify boundary elasticity as a control parameter governing the balance between vortical and ballistic dynamics.

Curvature in two-dimensional (2D) materials presents an effective approach for modulating their electronic structures and nonlinear optical properties; however, its influence on transition metal dichalcogenides (TMDs) remains insufficiently understood. In this study, we introduce a straightforward method to convert monolayer WS2 into quasi-one-dimensional nanoscrolls via solvent-assisted rolling on metallic substrates, yielding a curved multilayer architecture characterized by pronounced strain gradients and symmetry breaking. The resulting WS2 nanoscrolls demonstrate an enhancement in second-harmonic generation (SHG) exceeding 4 orders of magnitude (up to 1.4 × 104) compared to monolayers, accompanied by significant amplification of Raman scattering signals. We attribute this substantial nonlinear optical response to the combined effects of curvature-induced inversion symmetry breaking, coherent interlayer coupling, and strain-mediated modulation of the nonlinear susceptibility. In addition, the metallic substrate significantly modifies the local electromagnetic environment through mirror-induced field enhancement and increased radiative decay channels, leading to enhanced local fields and improved emission efficiency, which further contribute to the observed signal amplification. Polarization-resolved SHG measurements reveal pronounced anisotropy consistent with strain-induced redistribution of nonlinear tensor components, while Raman and photoluminescence analyses confirm the coexistence of tensile and compressive strain, leading to phonon softening and bandgap narrowing. These findings highlight the important role of curvature in manipulating light-matter interactions in 2D materials and propose a generalizable strategy for engineering enhanced nonlinear responses in van der Waals systems beyond conventional planar configurations.

A two dimensional classical ferromagnetic XY model with its bound vortex-antivortex dominated quasi long range ordered phase at low temperatures is a long standing as well as well studied problem of interest in the field of condensed matter. We conduct a detailed Monte Carlo study of such model in a square lattice with rather unexplored extensions where additional anisotropic exchange coupling and Dzyaloshinskii-Moriya interactions (DMI) together affect the Kosterlitz-Thouless (KT) transition in presence/ absence of symmetry breaking fields. Without DMI, the exchange term promotes collinear (ferromagnetic) order, whereas the DMI term induces spin cantings. By tuning anisotropy upto Ising limit, we document energy, specific-heat, magnetizations as well as helicity modulus and vortex densities for different temperatures and DMI strength. We also compute the 2nd moment of correlation lengths in order to probe the spatial correlation of the spins. Furthermore, the effect of U(1) symmetry breaking 4-fold and 8-fold symmetric h4 and h8 fields are explored which shows how the double-peaked specific heat profiles changes in presence of DMI. Overall, our findings append many important updates in the low temperature phases of a topological XY ferromagnet when additional DMI and isotropy-breaking exchange and/or field terms are considered thereby providing a few practical blueprints for suitably engineering topological spin systems.

The origin of superconductivity in oxide interfaces and its relation to ferroelectricity remains an open question. At LaAlO3/SrTiO3 interfaces, quantum confinement and inversion symmetry breaking create a two-dimensional electron gas near a ferroelectric quantum critical point, yet direct evidence linking phonon dynamics to electron pairing has been lacking. Here we directly probe lattice vibrations and atomic structure at LaAlO3/SrTiO3 interfaces across the superconducting phase diagram using vibrational spectroscopy with momentum selectivity in a scanning transmission electron microscope. We find that superconductivity across the doping series correlates with inversion symmetry breaking and the appearance of high-frequency localized phonons. These tunable, polar vibrations-confined near the interface-exhibit strong electron-phonon coupling and evolve systematically with carrier density. Our findings establish a link between lattice instability, superconductivity and strong electron-phonon coupling mediated by tunable localized phonons, providing new insights into possible microscopic pairing pathways in quantum paraelectric systems.

The Rise of Janus 2D Hexagonal Materials: Broken Symmetry, Emergent Properties, and Device Opportunities.

A spacetime crystal is a phase of matter that spontaneously develops periodic order in both space and time. Spacetime crystals have been experimentally observed in microscopic quantum many-body systems and, very recently, in a mesoscopic nematic liquid crystal. However, the melting process of a spacetime crystal and its underlying physical mechanisms have not yet been experimentally reported. Here, we present a direct observation of a classical continuous spacetime crystal melting in a table-top experiment with macroscopic active granular disks in 2 + 1 spacetime dimensions. The spacetime crystal is characterized by the spontaneous formation of a coherent, rigid-body rotation of a 2D triangular lattice that persists for almost a day and remains remarkably robust to noise. By tuning the disk packing fraction, we observe a complex three-stage melting process involving a spatially hexatic phase and multiple coexistence regions. Importantly, we show that spatial and temporal crystalline orders melt separately through distinct mechanisms: Spatial order is destroyed by the proliferation of topological defects, while temporal order is lost through the decay of directional persistence caused by the progressive weakening of many-body interactions. Our results demonstrate that the spontaneous breaking of spatial and temporal translational symmetries can be decoupled, leading to the emergence of exotic out-of-equilibrium classical phases of matter.

Chiral quasi-bound states in the continuum (q-BICs) have recently emerged in metaphotonics as resonances that combine ultra-high-quality factors with near-unity circular polarization in the far field. However, these states are typically confined to the Γ-point (normal incidence) due to their symmetry-protected origins. We propose a new mechanism for realizing light-cone-proximal chiral q-BICs at large oblique angles, enabled by the divergence of the radiative density of states near the light cone. Using dielectric metasurfaces with a monoclinic lattice and broken in-plane mirror symmetry, we demonstrate that tuning the lattice angle allows for robust control of these resonances. The resulting chiral q-BICs exhibit near-unity circular dichroism in transmission and fully circularly polarized emission at angles exceeding 50° from normal. Our results establish a general route to off-normal and grazing-angle chiral q-BICs, enabling directional chiral lasing and providing a versatile platform for quantum and nonlinear photonics.

The electrocatalytic nitrate reduction reaction (NO3RR) serves as a dual-functional strategy for simultaneous ammonia production and nitrate pollutant removal. However, the rational design of high-performance catalysts is often hindered by a limited understanding of catalyst structure-activity relationships at the molecular level. Here, this study systematically investigated the reaction mechanisms of three cobalt-based molecular catalysts: Co(DIM), Co(cyclam), and Co(TIM) with similar ligand structures for NO3RR, combining in situ bipolar electrode electrochemical mass spectrometry (BPE-EC-MS) and theoretical calculations. This approach elucidates the influence of ligand structure on reaction pathways and catalytic performance. Using high-temporal-resolution BPE-EC-MS, key intermediates such as [Co(DIM) + H2NO + OH─H]- were directly observed for the first time. Integrated mass spectrometry and theoretical simulations reveal that the electronic effects of ligands are the core factors governing catalytic performance. Co(DIM) achieves optimal catalytic performance by redistributing electron density to ligands through molecular symmetry breaking and electron storage via double bonds; simultaneously, its amino protons thermodynamically and kinetically synergize with reaction progression through intramolecular hydrogen bonding and proton transfer. This study provides both methodological tools and theoretical foundations for the rational design of high-efficiency molecular NO3RR catalysts.

Switchable polarization makes ferroelectrics a critical component in memories, actuators, and electro-optic devices, and potential candidates for nanoelectronics. A strain-induced preferential 90° polarization switching in ferroelectric oxides is highly desirable for achieving enhanced electromechanical response. However, such strain-induced switching typically proceeds along random paths under tensile strain in two opposite directions, which is unfavorable for electromechanical device performance. Here, we propose a strategy that leverages miscut-angle-driven in-plane symmetry breaking to preferentially control the 90° polarization switching path in freestanding PbTiO3 (PTO) films under uniaxial strain. Theoretical calculations highlight the key role of miscut substrates in manipulating the energy landscape during strain engineering. A combination of in situ X-ray diffraction and vector piezo-response force microscopy measurements directly reveals that preferential 90° polarization switching can be achieved by engineering in-plane symmetry. This work establishes design principles for controlling 90° polarization switching paths in freestanding ferroelectric oxides for high-performance electromechanical devices.

Intercalating a Pb monolayer between graphene and SiC(0001) creates a densely packed metallic layer in close proximity to graphene. Using low-temperature four-point-probe scanning tunneling microscopy and density functional theory, we correlate the local conductivity of this two-dimensional heterostructure with spatially resolved spectroscopy. By varying the tunneling gap, we distinguish the density-of-states contributions of the decoupled graphene sheet and the buried Pb interface layer. At large tip-sample separations, the spectra resemble those of charge-neutral, quasi-freestanding graphene with a small contribution of the metallic Pb layer beneath. This separation confirms the presence of a 5 meV energy gap in graphene, primarily arising from symmetry breaking induced by the epitaxial Pb layer. A proximity-induced intrinsic spin-orbit coupling appears negligible or is compensated by Rashba-type interactions.

Zirconium/hafnium fluorides have recently garnered considerable interest as potential optical materials, owing to their short ultraviolet (UV) cutoff edges. Transforming centrosymmetric (CS) structures into noncentrosymmetric (NCS) analogues through cationic regulation has proven to be an effective approach for the development of nonlinear-optical (NLO) materials. Herein, various Zr/Hf-based fluorides with different alkali-metal cations, including K8M5F28(H2O) (M = Zr(1), Hf(2)), CsNaHfF6 (3), and LiK10M6F35(H2O)2 (M = Zr(4), Hf(5)), were synthesized. 1-3 belong to centrosymmetric space groups, whereas 4 and 5, incorporating the Li+ cation with a small radius, exhibit NCS crystal structures. 1 and 2 feature chain-like anionic structures. 3 presents a zero-dimensional (0D) anionic structure constructed from isolated [HfF6]2- octahedra. Compounds 4 and 5 adopt three-dimensional (3D) anionic networks. The introduction of Li+ enhances structural distortion and dipole alignment, resulting in phase-matchable (PM) second-harmonic-generation (SHG) responses. Notably, all compounds exhibit UV absorption edges below 200 nm, confirming superior UV transparency. Overall, these results indicate that alkali-metal regulation is an efficient approach to trigger symmetry breaking while concurrently enabling SHG activity and maintaining short UV absorption edges.

In the low Reynolds number regime, active biological systems utilize nonreciprocal cyclic activities to achieve motility, as seen in the spinning of bacterial flagella and the beating of cilia. Coupling among these active mechanical components leads to synchronization and emergence of metachronal waves. Here, we report that biofilms of Pseudomonas nitroreducens form active carpet-like surfaces textured with diverse topological defects, generating Mexican-wave-like collective behavior in which bacteria periodically lift up. On these active surfaces, non-reciprocally coupled extension and retraction activities of bacterial pili drive these collective oscillations. Surprisingly, this collective behavior exhibits left-right asymmetry across the biofilm driving unidirectionally propagating waves. We discover that this directionality is primarily governed by an aging-related frequency gradient across the biofilm. Leveraging these insights, we further demonstrate the ability to control the collective dynamics of these waves, including symmetry breaking, transitions from spiral waves into target and propagating plane waves by manipulating the elastic properties of biofilms. Overall, our findings illuminate the fundamental role of nonreciprocally interacting active components in regulating synchronization, collective dynamics, and symmetry-breaking phenomena in biological systems.

We report a dynamical phase transition from integrability to nonintegrability in a simple oval-like billiard with boundary . For ϵ = 0, the phase space is foliated by invariant curves corresponding to periodic or quasiperiodic motion, whereas for small ϵ a thin chaotic layer separates rotational and librational trajectories. As ϵ increases, this layer grows according to a well-defined scaling law whose chaotic dispersion follows , where the exponent coincides with those of the Fermi-Ulam model, periodically corrugated waveguides, and a family of discrete mappings, revealing a universal mechanism for the onset of chaos in weakly perturbed integrable systems. The deviation of the reflection angle in the billiard, , acts as an order parameter: it vanishes continuously as , signalling an ordered (integrable) phase, while its susceptibility diverges, indicating a second-order phase transition. A symmetry breaking and an analytically solvable diffusion process complete the near-critical phenomenology. These results establish a unified framework for the emergence of chaos from integrability.

Symmetry breaking and phase transitions in random non-commutative geometries and related random-matrix ensembles

The phenomenon of intriguing Rashba spin splitting, which is driven by intrinsic structural symmetry breaking and spin-orbit coupling (SOC), has been observed in various perovskite materials. However, it remains unclear how phonon vibrational frequency affects spin carrier dynamics in two-dimensional perovskites exhibiting the Rashba effect. A thorough exploration of the electronic structures and the mechanism behind the strain-induced lattice vibration on spin dynamics in Ruddlesden-Popper (RP) Cs2GeI2Cl2/InSe heterostructure is presented herein, based on nonadiabatic molecular dynamics (NAMD) simulations with spin-orbit coupling (SOC) and density functional theory. Remarkably, the bandgap magnitudes and the extent of spin splitting within the Cs2GeI2Cl2/InSe heterostructure has been significantly increased under compressive strain (ε = -4%). This enhancement is attributed to the decrease of the in-plane Ge-Cl bond length, which results in stronger Coulomb interaction and increased distortion of the [GeI2Cl4]4- octahedral. When applying compressive strain on the heterostructure, more high frequency phonons (200-1000 cm-1) participate in carrier relaxation process, leading to ultrafast spin dynamics (310.01 fs). The frozen phonons NAMD results show that high-frequency phonons promote carrier transfer more than low-frequency phonons in the 2D perovskite-based heterostructure. Interestingly, the Rashba spin dynamics also can be manipulated by the temperature, revealing that the phonon vibrational frequency is temperature-dependent. These findings highlight the importance of high-frequency phonons on Rashba spin dynamics in perovskite-based photoelectronic devices.

Two-dimensional β'-In2Se3 hosts coexisting ferroelectric, antiferroelectric, and ferroelastic orders, yet the microscopic origin of its strain-driven ferroelastic switching remains unclear. Here, we demonstrate that strain can effectively modulate the in-plane polarization orientation variants of β'-In2Se3 by reshaping a Mexican-hat-like potential energy landscape. Using first-principles calculations, we show that β-In2Se3 is dynamically unstable and transforms into β' through an in-plane displacement of the central-layer Se atoms (Se-CL), which follows a continuous Mexican-hat-like potential. Mechanical strain reshapes this potential: biaxial strain preserves its rotational symmetry, whereas uniaxial strain breaks it, converting the Mexican-hat-like profile into an anisotropic canyon-like landscape that lifts valley degeneracy. This symmetry breaking pins the Se-CL displacement direction and thereby controls the orientation of in-plane ferroelastic variants. This study reveals the microscopic coupling between lattice distortion and domain switching in 2D ferroelastics, highlighting their potential for strain-controlled, low-power 2D ferroic devices.