Papers

Magnetostatic surface spin wave (MSSW) solitons hold great promise for magnonic information processing, but their existence has long been debated. In this work, we resolve this issue by advanced time-resolved Brillouin light scattering (TR-BLS) spectroscopy. We observe long-period MSSW soliton trains in yttrium iron garnet (YIG) thin films by demonstrating their quasiparticle behavior, mode beating, and periodic modulations. We reveal that the MSSW soliton originates from the dipole gap mechanism with a unique comb-like frequency spectrum caused by the four-magnon process. By varying the microwave power, we find significant changes in soliton periods linked to the spin wave dispersion renormalization. Additionally, we report exotic transverse solitons across the YIG thickness. These findings deepen the understanding of nonlinear physics, and pave the way for spin-wave-soliton-based information technologies.

The cobalt-based honeycomb magnet BaCo$_2$(AsO$_4$)$_2$ (BCAO) has recently emerged as a promising platform for frustrated magnetism beyond conventional paradigms. Neutron-scattering experiments and first-principles calculations have revealed an unexpected double-zigzag (dZZ) magnetically ordered ground state, whose microscopic origin remains under active debate. Here, we revisit this problem within a ferro–antiferromagnetic $J_1$–$J_3$ Heisenberg model on the honeycomb lattice using a generalized Schwinger-boson mean-field theory (gSBMFT) that treats ferromagnetic and antiferromagnetic interactions on equal footing. This approach, combined with exact diagonalization (ED), allows us to demonstrate the emergence of the dZZ phase in a narrow parameter range, stabilized by quantum fluctuations through an order-by-disorder mechanism, in good agreement with recent density-matrix renormalization-group (DMRG) results. We further characterize the associated magnetic excitations and discuss their relevance to recent inelastic neutron-scattering (INS) measurements on BCAO.

The theory of the intrinsic nonlinear Hall effect, a key probe of quantum geometry, is plagued by conflicting expressions for the conductivity that is independent of the dissipation strength (rate, $\Gamma^0$). We clarify the origin of this ambiguity by demonstrating that the "intrinsic" response is not universal, but is inextricably linked to the dissipation mechanism that establishes the non-equilibrium steady state (NESS). We establish a benchmark by solving the exact NESS density matrix for a generic Bloch system coupled to a featureless fermionic bath. Our exact $\Gamma^0$ conductivity decomposes into two parts: (i) a geometric contribution, $\sigma^{\text{geo}}$, whose form recovers the intraband quantum metric contribution ($\sim\partial_k g$), providing an exact derivation that clarifies inconsistencies in the literature, and (ii) a novel, purely kinetic contribution, $\sigma^{\text{kin}} \propto v^3 f^{(4)}_0$, which is absent when dissipation is modeled by white-noise disorder (e.g., a constant-$\Gamma$ Green's function model). The discrepancy in $\sigma^{\text{kin}}$ between these distinct physical mechanisms is a proof that the $\Gamma^0$ nonlinear conductivity is not a unique property of the Bloch Hamiltonian, but is contingent on the physical system-bath coupling.

Altermagnets are a class of collinear magnets that exhibit non-relativistic spin splitting (NRSS) of electronic bands in the absence of net magnetization. Their potential to generate large spin polarization without spin-orbit coupling has created strong interest in probes that access the underlying order parameter directly. In this Perspective, we show that linear magneto-birefringence (LMB) provides a natural and broadly applicable route to detecting altermagnetic order. Building on the correspondence between the momentum-space structure of NRSS and the ferroic ordering of magnetic multipoles in real space, we demonstrate how $d$-wave and $g$-wave NRSS textures yield distinct LMB responses. We present a symmetry-based framework that identifies the optical geometries and field configurations required to isolate specific multipole components, enabling domain imaging and providing benchmarks for theoretical models of LMB.

The non-Hermitian skin effect (NHSE), characterized by the accumulation of a macroscopic number of bulk states at system boundaries, is a hallmark of non-Hermitian physics. However, in higher dimensions, achieving deterministic control over where skin modes accumulate remains a major challenge. Here, we propose a versatile route to program the skin-mode localization site in two-dimensional non-Hermitian lattices by combining disorder with a static electric field. While the electric field alone suppresses the NHSE in a clean system, the introduction of disorder induces transverse wave-packet transport perpendicular to the field. In nonreciprocal lattices, when the nonreciprocal hopping is misaligned with the electric field, the hopping component perpendicular to the field guides wave-packet propagation and produces boundary localization. By tuning the relative orientation between the electric field and the nonreciprocal hopping direction, the boundary localization position can be continuously and arbitrarily controlled. We further demonstrate distinct geometry-dependent manipulation of skin modes in reciprocal lattices, where controllable boundary localization emerges solely from the lattice geometry. Our results establish a robust and broadly applicable route to engineer boundary accumulation and directed transport along prescribed directions in two-dimensional non-Hermitian systems, enabling reconfigurable wave routing in classical platforms and programmable transport functionalities in quantum settings.

We reveal the key role of the $d$-wave symmetry of the superconducting gap in strongly coupled two-dimensional superconductors in determining the properties of the Berezinskii-Kosterlitz-Thouless (BKT) transition, associated with a sizable enhancement of the phase stiffness compared to nodeless-gap superconductors. The enhanced stiffness originates from extended regions of vanishing gap around the nodal lines of the Brillouin zone (BZ). Our study, based on mean-field and BKT theory, presents a comparative analysis of $s$-wave and $d$-wave scenarios, highlighting the features of the latter that boost the stiffness and the BKT transition temperature (T$_{BKT}$). The comparison focuses on two quantities: the mean-field critical temperature and the maximum superconducting gap related to the pairing strengths. We present a phase diagram showing the scaling of T$_{BKT}$ with respect to the mean-field critical temperature across the BCS-BEC crossover and the evolution of the pseudogap. We also present a zero-temperature phase-stiffness intensity map over the Brillouin zone, displaying a two-component structure consisting of low- and high-stiffness regions whose extent depends on microscopic parameters. These results identify the nodal gap structure of strongly coupled two-dimensional superconductors as a key mechanism enabling enhanced stiffness and elevated T$_{BKT}$ compared to their $s$-wave counterparts.

Understanding electrochemical phenomena at complex liquid solid interfaces requires linking real time structural dynamics with atomic scale interfacial chemistry. Here, we integrate operando synchrotron X-ray fluorescence and diffraction with high resolution cryogenic electron and ion multi model microscopy to provide a mechanistic understanding of Pt based alloying anodes across length scales. We directly observe the initial lithiation driven formation of Li2Pt and its evolution to a stable LiPt intermetallic phase during extended cycling via a solid solution type reaction mechanism. Simultaneously, the solid electrolyte interphase transitions from an unstable carbonate rich to a stable LiF dominated composition, confirmed by cryogenic scanning transmission electron microscopy and electron energy loss spectroscopy. Crucially, cryogenic atom probe tomography reveals spatially distinct compositional regimes within the alloy anode, including lithium flux limited, heterogeneous interfacial zone and a diffusion controlled, homogeneous LiPt alloy bulk. This nanoscale compositional gradient rationalises the emergent solid solution reaction mechanism and highlights how kinetic limitations and interface dynamics govern alloy formation and electrochemical stability. Our findings demonstrate a broadly applicable correlative framework bridging operando structural dynamics with near atomic resolution interfacial chemistry, advancing the rational design of durable alloy electrodes for next generation energy storage.

Coagulation-flocculation of pollutants and chelation of heavy metal ions are two widely used techniques in wastewater purification. Despite the differences between their respective mechanisms and inherent length scales, they bear much similarity on a larger scale, and can both be treated as adsorption of obstacles on a polymer structure. In this regime, their adsorbing efficiency is predominantly affected by conformation statistics of involved polymers, and this approach has been used in our previous studies based on lattice polymer model for a linear polymer adsorbent. There is a strong experimental evidence that branched adsorbents are more efficient than their linear counterparts. In this study we focus on two simplest representatives of the core-shell branched architectures: the star-like (with zero-dimensional point-like core) and comb-like polymers (with one-dimensional rigid core) with various number of branches, $f$, branch lengths, $N$, and branches separations, $S$ (for the case of comb-like structure). The polymers are grown on a lattice using the Monte Carlo simulations with the pruned-enriched Rosenbluth algorithm. The quantitative estimates for adsorption capacity in terms of adsorbed obstacles per monomer and the average number of bonds per adsorbed particle (average adsorption strength) have been evaluated in a wide range of parameters $f$, $N$, and $S$. Both the case of implicit diffusion of obstacles (with averaging over different arrangements of immobilized obstacles) and explicit diffusion of obstacles (allowing to study dynamics of adsorption process) have been analyzed. We found that comb-like polymers display the higher adsorption capacity but lower adsorption strength, comparing to the star-like polymers, and these effects are more pronounced with increasing branches separations $S$.

In this work, we present web scraping techniques to extract in- formation from patent tables, clean and structure them for future use in predictive machine learning models to develop new glasses. We extracted compositions and three properties relevant to the development of new glasses and structured them into a database to be used together with information from other available datasets. We also analyzed the consistency of the information obtained and what it adds to the existing databases. The extracted liquidus temperatures comprise 5,696 compositions; the second subset includes 4,298 refractive indexes and, finally, 1,771 compositions with Abbe numbers. The extraction performed here increases the available information by approximately 10.4% for liquidus temperature, 6.6% for refractive index, and 4.9% for Abbe number. The impact extends beyond quantity: the newly extracted data introduce compositions with property values that are more diverse than those in existing databases, thereby expanding the accessible compositional and property space for glass modeling applications. We emphasize that the compositions of the new database contain relatively more titanium, magnesium, zirconium, niobium, iron, tin, and yttrium oxides than those of the existing bases.

We explore several aspects of categorical symmetry-resolved entanglement entropy (SREE) directly within two-dimensional rational conformal field theory (RCFT) (without invoking any SymTFT construction arXiv:2409.02806). We derive a general formula applicable whenever the action of the relevant topological defect lines on the annulus Hilbert space is known. This framework accommodates weakly and strongly symmetric boundaries, cloaking states, and fusion rings with multiplicities. We verify the formula in a range of diagonal unitary and non-unitary examples, including theories with generalized Haagerup-Izumi modular data. Furthermore, we extend the analysis to non-diagonal RCFTs. The $\frac{1}{2}E_6$ example demonstrates that closed-channel modular data and NIM-rep multiplicities alone do not suffice to determine the defect action on the complete open-channel Hilbert space.

The cytoplasm is a heterogeneous mixture containing many types of proteins that self-assemble into a wide variety of complexes. The accuracy and speed of cytoplasmic self-assembly is astonishing because it involves the correct identification of components shared among different structures, despite pervasive thermal fluctuations. Typical toy models of self-assembly are based on the specificity of binding energies among components. However, kinetics plays a key role in biological self-assembly, often catalyzed by a plethora of assembly factors. Building on this observation, we extend a previous heteropolymer growth model to describe the retrieval of two-dimensional structures via quasi-2D growth. We find that the self-assembly of structures in this model is subject to strong speed and encoding bottlenecks. Moreover, we show that these bottlenecks can be suppressed by increasing the connectivity of a small fraction of components. This mechanism of kinetically controlling a small number of critical binding events provides a simple explanation for the timely assembly of large protein, and suggests a unifying principle for the role of assembly factors.

The band structure of elementary excitations of skyrmion crystal in thin ferromagnetic film with Dzyaloshinskii-Moriya interaction and uniaxial magnetic anisotropy under external magnetic field is studied. In the absence of anisotropy there is a topological transition in the spectrum of skyrmion crystal: the gap between breathing and counter-clock-wise modes closes, which is accompanied by changes of Berry curvature sign of these bands. In this work we demonstrate that such topological transition exists in some range of the uniaxial anisotropy values. We present a phase diagram showing that the value of the field of topological transition is higher in the easy-plane domain and lower in the easy-axis domain of anisotropy.

The Simmons model is a well-known and widely used model for the elastic tunneling current of a metallic tunnel junction, and fitting it to electrical measurements can be used to estimate thicknesses and heights of the tunnel barriers. We present here an improvement of the Simmons model, deriving new more accurate analytical formulas for the tunneling current density and conductance at finite voltage and temperature. We demonstrate that our conductance-voltage formulas are much closer to the Wentzel-Kramers-Brillouin approximation than the Simmons model and its commonly used simplified parabolic approximation. In addition, we demonstrate the practical use of our model, by fitting it to experimental tunnel junction conductance-voltage data and showing a sizeable difference from the Simmons model.

Hyperbolic lattices extend crystallinity into curved space, where negative curvature and exponentially large boundaries reshape collective excitations beyond Euclidean intuition. In this Letter, we push the study beyond scalar fields by exploring vector fields on hyperbolic lattices. Using phonons as an example, we show that the Goldstone theorem breaks down for vector fields in hyperbolic lattices. In stark contrast to Euclidean crystals, where the Goldstone theorem ensures that acoustic phonon modes are gapless, hyperbolic lattices with coordination number $z > 2d$ exhibit a finite bulk phonon gap. We identify the origin of this breakdown: the Goldstone modes here belong to nonunitary representations of the translation group and therefore cannot form gapless excitation branches. We further show that when boundaries are included, this bulk spetrum gap is filled by an extensive number of low-frequency boundary modes.

We compute and track the impact of truly nonlocal-correlation effects on the quasi-particle (QP) band-structure of hexagonal boron-nitride (h-BN) systems. To that end, we start with the consistent-exchange vdW-DF-cx version [PRB 89, 035412 (2014)] of the van der Waals density functional (vdW-DF) method [JPCM 39, 390001 (2020)] for exchange-correlation (XC) functional design and enforce piece-wise linearity in the energy changes with partial charging, using the Koopmans-integer (KI) DFT framework [JCTC 19, 7079 (2023)]. Our approach and results (denoted KI-CX) extends present-standard use of KI DFT (denoted KI-PBE as it is based on the semilocal PBE [PRL 77, 3865 (1996)] XC functional) to capture, for example, the impact of the interlayer coupling on the QPs. We contrast KI-CX and KI-PBE results for the QP band-structure and compare with both $GW$ calculations and experimental observations of the (direct and indirect) QP gaps. We find that KI-CX brings improvements in the h-BN QP energy description and generally agrees with $GW$ studies.

Soft solids exhibit instability and develop surface undulations due to surface effects, a phenomenon known as the elastic Plateau-Rayleigh (PR) instability, driven by the interplay of surface and bulk elasticity. Previous studies on the PR instability in solids mainly focused on the case of constant surface tension and ignored the effect of surface elasticity. It has been shown by experiments that the surface effects in solid-like materials depend both on the surface tension and surface elasticity, but little is known about the role of the latter in the elasto-capillary instabilities in soft solids. Here, we conduct an in-depth exploration of the effect of surface elasticity on the PR instability in an elastic cylinder by coupling theoretical and numerical methods. We derive an asymptotically consistent one-dimensional (1d) model to characterize the PR instability from three-dimensional (3d) nonlinear bulk-surface elasticity, and develop a new finite-element (FE) scheme for simulating 3d deformations of the bulk-surface system. The initiation and evolution of the PR instability are obtained analytically with the aid of the 1d model. The 1d results are further validated by the 3d FE simulations. By synthesizing the 1d analytic solutions and 3d numerical results, the effects of surface elasticity, surface compressibility, surface tension, axial force and geometrical size on the PR instability are thoroughly elucidated. Our results can be applied to calibrate surface parameters for solid-like materials and develop constitutive models for elastic surfaces.

We develop a framework to describe collective buckling in metal-organic frameworks (MOFs). Starting from the microscopic structure of a single organic linker, we define a buckling coordinate governed by an effective double-well potential. Coupling between linkers is introduced within a dipole-dipole approximation, resulting in an effective lattice Hamiltonian. We analyze the transition between ordered and disordered phases within a mean-field approximation and estimate the critical temperature. As an illustrative example for our theory, we discuss the collective buckling instability for the prototypical cubic framework MOF-5 under different values of uniaxial strain. Our approach provides a quantitative description of collective buckling in framework materials.

Optical cavities provide a powerful means to engineer light-matter hybrid states by coupling confined electromagnetic fields with matter excitations. Achieving in situ control of the coupling strength is essential for investigating how such hybridization evolves with the coupling strength. In this work, we use a symmetry-changing structural phase transition in lead halide perovskites to reversibly tune the phonon-photon coupling strength, leveraging the fact that their phonon frequencies and oscillator strengths are dictated by lattice symmetry. Terahertz time-domain spectroscopy of MAPbI3 embedded in nanoslot cavities reveals three polariton branches above the critical temperature Tc = 162.5 K, and the emergence of an additional branch below Tc, activated by a new phonon mode in the low-temperature phase. The full dispersion is accurately reproduced using a multimode Hopfield model, confirming that all normalized coupling strengths remain in the ultrastrong coupling regime. These results demonstrate symmetry-controlled tuning of ultrastrong coupling via phonon engineering in optical cavities.

The Comment [Y.-M. Li, B. Wei, and K. Chang, Phys. Rev. Lett. 132, 219601 (2024)] pointed out that it is incorrect to predict the temperature-driven topological phase transition of Dirac magnons in honeycomb ferromagnets with Dzyaloshinskii-Moriya interactions based on the theory in Lu et al. [Y.-S. Lu, J.-L. Li, and C.-T. Wu, Phys. Rev. Lett. 127, 217202 (2021)]. Here we propose that by breaking the sublattice symmetries in honeycomb ferromagnets, increasing temperature could induce topological transitions from the trivial phase at zero temperature based on the linear spin wave theory to the Chern insulating phase above a critical temperature without changing any spin-spin interactions. The key to the finite-temperature topological magnons is considering the magnon-magnon interactions (MMIs) at a mean-field level. A self-consistently renormalized spin wave theory is employed to include self-energy corrections from MMIs, guaranteeing that the critical temperatures for topological transitions are below the Curié temperatures. Across the critical temperatures, the magnon band gap closes and reopens at K or K? points in the Brillouin zone, accompanied by nontrivial Berry curvature transitions. However, in stark contrast to the work of Lu et al. [Phys. Rev. Lett. 127, 217202 (2021)], the topological transitions cannot be revealed by the thermal Hall effect of magnons. Our work provides a realistic scheme for achieving a finite-temperature topological phase in honeycomb ferromagnets.

Quantum batteries are quantum mechanical systems able to store and release energy in a controlled fashion. Among them, a special role is played by quantum structures defined as networks of two-level systems. In this context, it has recently been shown that the energy stored in free fermion quantum batteries is sensitive to the quantum phase diagram of the battery itself. This sensitivity is relevant for stabilizing the stored energy and designing optimal charging protocols. In this article, we explore universal charging behaviors of free fermion quantum batteries across quantum phase transitions. We first analyze a Dirac cone-like model to extract general features. Then, we verify our findings by means of two relevant lattice models, namely the Ising chain in a transverse field and the Haldane model.

We report the successful growth of epitaxial layers of van der Waals (vdW) lead oxide (PbO) polymorphs on different substrates, via pulsed laser deposition. A thin layer of vdW ${\alpha}$-PbO (~5 nm) was subsequently used as a virtual substrate to grow thin films of perovskites BaTiO$_3$, SrTiO$_3$, and the spinel CoFe$_2$O$_4$ with a crystal quality comparable to direct epitaxy on single-crystal oxide substrates. Notably, films with the larger lattice parameter underwent spontaneous, controlled spalling within days of growth, remaining structurally intact, or were easily exfoliated and transferred using the tape method. This work establishes PbO as a promising virtual substrate technology for the fabrication of free-standing oxide membranes through vdW epitaxy, offering advantages over conventional sacrificial layer methods.

Janus derivatives of 2H MX2 (M = Mo/W; X = S/Se), namely MSSe, have already been experimentally realized and explored for applications in photocatalysis, photovoltaics, and optoelectronics. Focusing on the photocatalytic properties of these layers, we investigate the adsorption of atomic hydrogen on the MSSe layers in the presence of metalloid dopants B, Si, and Ge. The layers in their pristine form exhibit positive adsorption energies, indicating an endothermic nature. Substitution of a dopant in the pristine MSSe layers alters the local symmetry, bonding character, and charge distribution, thereby increasing the number of active sites for hosting H adsorption and reducing the adsorption energy. We select distinct sites, both atomic and interstitial, for the substitution of dopants. The energetics of the H atom at various sites is studied to find the most favorable active site on the MSSe Janus layers. Our results based on density functional theory calculations show that the adsorption process becomes spontaneous and less attractive in the presence of atomic site dopant substitution, whereas the interstitial site results in an endothermic behavior. Moreover, having the data from DFT, we develop a supervised machine learning model for predicting the hydrogen adsorption energy. For this purpose, we utilize 23 elemental features of the atoms involved in the structure, thereby eliminating the need for DFT calculations in feature design. The dimensionality reduction technique, principal component analysis, is employed to reduce the dimensionality of the feature space, yielding independent features that are mutually orthogonal. The model is implemented as a multi-layer perceptron regressor with two hidden layers. The data augmentation technique is employed to artificially expand the dataset size, thereby enhancing the accuracy of the neural network model by 0.90% on the testing data.

A generalized version of the Wilson-Cowan (WC) model is proposed which accounts for the evolution of the synaptic resources. Adiabatic elimination of the fast variables is performed to yield a simplified framework for the coupled interaction between active excitatory and inhibitory neurons. The latter model is shown to smoothly converge to the benchmark WC model, when the appropriate limit is performed. Different dynamical regimes are identified for the reduced model and commented upon with reference to the original formulation of the generalized dynamics. This includes identifying limit cycle oscillations for population of available resources.

Controlled fabrication of twisted van der Waals heterostructures is essential to unlock the full potential of moire materials. However, achieving reproducibility remains a major challenge, particularly for air-sensitive materials such as $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$ (BSCCO), where it is crucial to preserve the intrinsic and delicate superconducting properties of the interface throughout the entire fabrication process. Here, we present a dry, inert and cryogenic assembly method that combines silicon nitride nanomembranes (NMBs) with pre-patterned electrodes and the cryogenic stacking technique (CST) to fabricate high-quality twisted BSCCO Josephson junctions (JJs). This protocol prevents thermal and chemical degradation during both interface formation and electrical contact integration. We also find that asymmetric membrane designs, such as a double cantilever, effectively suppress vibration-induced disorder due to wire bonding, resulting in sharp and hysteretic current-voltage characteristics. The junctions exhibit a twist-angle-dependent Josephson coupling with magnitudes comparable to the highest-performing devices reported to date, but achieved through a straightforward and versatile contact method, offering a scalable and adaptable platform for future applications. These findings highlight the importance of both interface and contact engineering in addressing reproducibility in superconducting van der Waals heterostructures.

Driven particle transport in crowded and confining environments is fundamental to diverse phenomena across physics, chemistry, and biology. A main objective in studying such systems is to identify novel emergent states and phases of collective dynamics. Here, we report on a nonequilibrium phase transition occurring in periodic structures at high particle densities. This transition separates a weak-current phase of thermally activated transport from a high-current phase of solitary wave propagation. It is reflected also in a change of universality classes characterizing correlations of particle current fluctuations. Our findings demonstrate that sudden changes to high current states can occur when increasing particle densities beyond critical values.

The development of compact, energy-efficient integrated lasers operating at 1.3 um remains a critical focus in silicon photonics, essential for advancing data communications and optical interconnect technologies. This paper presents a numerical study of distributed Bragg reflector (DBR) hybrid III-V-on-silicon lasers, analyzing design trade-offs and optimization strategies based on supermode theory. The III-V section of the design incorporates InAs/(Al)GaAs quantum dots (QDs), which offer improved temperature insensitivity at the cost of more complex III-V/Si optical coupling, due to the high refractive index of (Al)GaAs. Consequently, many current laser designs rely on silicon waveguides with a thickness exceeding 220 nm, which helps coupling but limits their compatibility with standard CMOS technologies. To address this challenge, we perform detailed simulations focusing on 220-nm-thick silicon waveguides. We first examine how the mode profiles jointly depend on the silicon waveguide dimensions and the geometry and composition of the III-V stack. Based on this analysis, we propose a novel epitaxial design that enables effective III-V/Si coupling, with the optical mode strongly confined within the III-V waveguide in the gain section and efficiently transferred to the silicon waveguide in the passive sections. Moreover, the final design is shown to be robust to fabrication-induced deviations from nominal parameters.

The experimental observations of many interaction-driven electronic phases in moiré superlattices have stimulated intense theoretical and experimental efforts to understand and engineer these correlated physics. Strain is a powerful tool for manipulating and controlling the geometrical and electronic structures of moiré superlattices. This review provides a comprehensive introduction to the geometry of strained moiré superlattices. First, starting from the linear elasticity theory, we briefly introduce the general formalism of small deformations in two-dimensional materials, and discuss the particular cases of uniaxial, shear and biaxial strain. Then, we apply the theory to twisted and strained moiré materials, mainly focusing on the hexagonal homobilayers, hexagonal heterobilayers and monoclinic lattices. Special moiré geometries, like the quasi-unidimensional patterns, square patterns and hexagonal, are theoretically predicted by manipulating the strain and twist. Finally, we review recently developed strain techniques and the special moiré geometries realized via these approaches. This review aims at equipping the reader with a robust understanding on the description and implementation of strain in moiré materials, as well as highlight some major breakthroughs in this active field.

High-quality dielectric films are essential for fabricating advanced electronic devices, but their direct deposition often degrades the films and their underlying interfaces, which compromises device performance, especially on sensitive or low-adhesion surfaces. To overcome these limitations, film transfer methods enable the integration of high-quality dielectric films onto such surfaces without damaging the underlying interfaces. However, existing transfer methods have predominantly focused on high-dielectric-constant (high-$\kappa$) materials, leaving a critical gap for transferable, high-quality low-$\kappa$ alternatives, which are required for enabling low-power and high-speed electronics. Herein, we address this need by demonstrating a method to integrate freestanding low-$\kappa$ fluoropolymer dielectric films with smooth surface morphology onto diverse substrates, including low-adhesion surfaces like hydrogen-terminated diamond. The transferred films revealed high breakdown fields of ${8.0}\pm{1.2}$ MV cm$^{-1}$, with leakage current density remaining typically below ${10}^{-7}$ A cm$^{-2}$ before the breakdown. The incorporation of these fluoropolymer films as gate dielectrics in p-channel hydrogen-terminated diamond field-effect transistors resulted in transfer and output characteristics with negligible hysteresis, high channel mobility (${\approx}400$ cm$^{2}$V$^{-1}$s$^{-1}$) and a low interface trap density (${\le}3{\times}10^{11}$ cm$^{-2}$eV$^{-1}$). These findings highlight the versatility of the transfer method and position freestanding fluoropolymers as a promising platform for forming high-quality dielectric/semiconductor interfaces for advanced electronics.

We develop a variational neural-network framework to determine the most probable path (MPP) of a 3D active Brownian particle (ABP) by directly minimizing the Onsager-Machlup integral (OMI). To obtain the OMI, we use the Onsager-Machlup variational principle for active systems and construct the Rayleighian of the ABP by including its active power. This approach reveals geometric transitions of the MPP from in-plane I- and U-shaped paths to 3D helical paths as the final time and net displacement are varied. We also demonstrate that the initial and final boundary conditions have a significant impact on the MPPs. Our results show that neural optimization combined with the Onsager-Machlup variational principle provides an efficient and versatile framework for exploring optimal transition pathways in active and nonequilibrium systems.

We report on the evolution of tritium-induced sp$^3$-defects in monolayer graphene on a Si/SiO$_2$ substrate, by comparing large-area Raman maps of the same two samples, acquired just after fabrication and twice thereafter, about 9-12 months apart. Inbetween measurements the samples were kept under standard laboratory conditions. Using a conservative classification of sp$^3$-type spectra, based on the D/D' peak intensity ratio, we observed almost complete depletion of sp$^3$-type defects over the investigation period of about two years. This by far exceeds the ~5.5% annual reduction expected from tritium decay alone (~3x larger). This change in the defect composition is accompanied by a recovery of the 2D-band of graphene and an overall decrease in defect-density, as determined via the D/G intensity ratio. Hydogenated graphene is reported to be reasonably stable over several months, when kept under vacuum, but suffers substantial hydrogen loss under laboratory air conditions. While the results shown here for tritiated graphene exhibit similarities with hydrogenated graphene, however, some distinct differences are observed.