Papers

Oxidative stress is a key factor in low fertility outcomes during assisted reproduction technology (ART) and contributes to poor sperm quality. Conventional assessment relies on bright-field microscopy, which lacks the quantitative sensitivity to resolve subcellular structural and biophysical changes without exogenous contrast agents, a requirement that can introduce cytotoxic effects and compromise cell viability. This study uses QPM as a label-free, high-throughput method to demonstrate how ascorbic acid reduces the impact of oxidative structural degradation in Sahiwal bovine spermatozoa. To illustrate this pathology, severe oxidative stress was experimentally induced using hydrogen peroxide (H2O2), and two doses of ascorbic acid (1 mg/ml and 8 mg/ml) were tested to evaluate dose-dependent antioxidant recovery in structurally damaged sperm. QPM was used to quantify structural changes in key biophysical parameters, including dry mass, optical thickness, volume, surface area, sphericity, and surface area-to-volume ratio, as well as intracellular texture parameters. Under acute oxidative stress, bovine spermatozoa exhibited significant reductions in optical thickness and dry mass, alongside measurable changes in intracellular structural organization, collectively indicative of oxidative stress-induced morphological degradation. Co-treatment with ascorbic acid resulted in partial, dose-dependent structural preservation, with the 8 mg/ml formulation demonstrating statistically significant attenuation of these structural changes compared to the 1 mg/ml treatment group. These findings suggest that QPM-derived biophysical parameters may serve as promising, label-free structural indicators for characterizing oxidative damage in bovine spermatozoa. Future studies should incorporate functional validation to determine whether this structural preservation translates to improved outcomes in ART.

We identify a Hall response carried by optically induced interband coherence rather than by a non-equilibrium band population. In a weakly doped zinc-blende semiconductor, a longitudinal dc field drives a transverse flux of the conduction–valence coherence created by near-gap light. Angular averaging eliminates the homogeneous coherence density, while a lateral boundary converts the transverse flux into an antisymmetric, edge-localized, helicity-odd polarization. The resulting Kerr signal requires neither spin-orbit coupling nor a spin, valley, or orbital accumulation within an individual band. Within the eight-band Kane model, we derive the boundary kinetic equation and obtain a complex propagation length controlled by optical detuning and interband dephasing. The edge profile is monotonic at optical resonance and develops damped spatial oscillations away from it. The response is enhanced by electron–hole asymmetry and by strong interband mixing, making narrow-gap semiconductors especially favorable to observe the effect. These results establish dc-driven Kerr microscopy as a direct probe of an interband-coherence Hall effect and of multiband quantum kinetics in real space.

Novel experiments in transmission electron microscopy often require the development of specialized imaging and spectroscopy states, such as for flexible momentum-resolved high energy-resolution spectroscopy. This task is complicated by the need to align and configure many different lenses, and by ambiguity around the locations of various imaging and diffraction planes. Here we develop a versatile digital twin for simulating the electron beam trajectory throughout an electron microscope, and we develop the calibration procedures required for accurate prediction of microscope states. This allows the user to quickly and easily determine the correct lens values for setting up new condenser or projector modes. Automatic procedures to change lens settings and measure the resulting changes can be used to close the loop. With the accelerating development of machine learning and artificial intelligence tools, we also believe a physically-informed model of the microscope can serve as a valuable tool for automated microscopy and AI/ML integration.

A general implementation of the equation-of-motion (EOM) formalism for correlated many-body states is presented and applied to the description of collective excitations in atomic nuclei. While EOM approaches are traditionally formulated on top of independent-particle reference states, the present work extends the method to correlated reference states generated by modern many-body solvers. This formulation enables a consistent treatment of ground-state correlations and excited-state dynamics within a unified framework. Particular emphasis is placed on collective nuclear excitations employing chiral nuclear Hamiltonians in an ab initio context. The approach is motivated by the renewed interest in EOM techniques across several fields, including quantum chemistry and quantum computing, where they provide efficient and systematically improvable descriptions of excitation spectra. The present results demonstrate that the EOM framework offers a flexible and powerful tool for the microscopic description of nuclear spectroscopy beyond the traditional mean-field paradigm.

Understanding the evolution of magnetic order in the two-dimensional limit remains a central challenge in van der Waals magnets, where thermodynamic measurements are constrained by the femtogram-scale mass of exfoliated flakes. Here, microsecond pulse-heating nanocalorimetry is used to measure the heat capacity and magnetic entropy of CrSBr flakes down to the monolayer limit. The measurements reveal the entropy landscape associated with magnetic ordering, uncovering a decreasing interlayer transition temperature toward the monolayer limit and an entropy-derived effective moment per layer that increases with thickness toward the expected spin-only scale. Thermodynamic anomalies capture a crossover from bulk-like interlayer antiferromagnetism to a regime dominated by intralayer ferromagnetic correlations. A pronounced layer-parity effect further emerges, with odd-layer samples displaying an additional high-temperature contribution associated with uncompensated magnetic layers. Under in-plane magnetic fields applied along the easy axis, antiferromagnetic order is progressively suppressed, allowing extraction of a thickness-dependent characteristic suppression field reflecting weakened interlayer exchange coupling. Entropy analysis further reveals an extended regime of magnetic fluctuations persisting well above the interlayer ordering transition. Together, these results establish nanocalorimetry as a powerful thermodynamic probe of low-dimensional magnetism, providing direct access to magnetic entropy, exchange interactions, and dimensional crossover in atomically thin van der Waals magnets.

We investigate ultrasound attenuation and sound velocity shift in antiferromagnetic spin-1/2 XXZ chains in magnetic field. We relate the sound velocity shift to derivatives of the free energy with respect to exchange interactions, permitting its calculation with integrability techniques at any temperature. Using bosonization, we predict the sound velocity shift exhibits a quadratic temperature correction at low temperatures in the Tomonaga-Luttinger liquid phase. Close to the fully polarized phase, a universal behavior associated with z=2 quantum criticality is found. In the Tomonaga-Luttinger liquid phase, ultrasound attenuation obeys a scaling law as a function of wavelength and temperature. An enhancement of attenuation is obtained near the fully polarized phase.

Colloidal quantum dots (QDs) are attractive nanoscale emitters, yet their cathodoluminescence (CL) response remains poorly understood and often unstable under electron-beam excitation, limiting CL spectroscopy and electron-beam-based device processing. Here, we investigate the CL mechanism and strategies to improve its stability using highly photostable, structurally homogeneous giant-shell CdSe/CdS QDs combined with in situ CL and photoluminescence (PL) measurements. By identifying distinct signatures of excited states in both lifetime and spectral measurements, we demonstrate that the CL response is governed by electron-beam-induced charging. Charge accumulation drives multiexciton generation even at relatively low currents, leading to a pronounced blueshift, shorter average lifetimes, and rapid cathodobleaching. To test this further, we employ indirect excitation to reach sub-pA currents beyond the limits of typical electron beams, showing that neutral-exciton emission can be partially recovered and cathodobleaching mitigated, although charging cannot be fully suppressed. Furthermore, by replacing long insulating ligands with shorter ones, we improve charge drainage and strongly suppress biexciton formation. Together, these results show that biexciton formation can be controlled by limiting charge accumulation, providing a practical route toward stable CL for spectroscopy, imaging, and electron-beam-compatible photonic devices.

Two-dimensional photonic crystals (2D PhCs) enable fine-grained control over a broad set of Bloch modes without the constraints of band occupancy and natural crystal structures, and, as intrinsically open systems, serve as versatile platforms for exploring diverse topological phenomena. Here, we develop a theoretical framework inspired by the irreducible-representation formalism in solid-state physics, while explicitly incorporating key characteristics of photonic Bloch systems, such as radiative coupling and transverse condition. Within this framework, we study the symmetry origins of local k-space topology, e.g., bound-states in the continuum and optical vortex beams, and Berry phase in two representative systems. We further analyze, from a group-theory perspective, how tailored structural designs and targeted symmetry perturbations can be exploited to manipulate these topological features. In particular, we showcase the application of the formalism to Bloch modes from distinct truncation approaches and specify the preferable regimes for each, both under a generic $n$-band configuration. The analysis can thereby be readily extended to a wide range of artificial wave crystals beyond scalar Schrödinger-like operators and two-level treatment.

We present a study of the perovskite Ca0.4Sr0.6TiO3 using variable temperature transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD). At room temperature and below, PXRD shows that the material adopts an orthorhombic Pbcm structure analogous to the P-phase of NaNbO3. Above 380 K the material transforms to a tetragonal I4/mcm phase. The structural distortions of these phases can be described as a combination of modes and order parameters associated with the M, T, ${\Delta}$ and R-points of the Brillouin zone, each of which can be associated with a different set of superstructure reflections visible in X-ray and electron diffraction patterns. For the I4/mcm phase only the expected R-point reflections are observed in PXRD while both M and R- reflections are observed in electron diffraction. Using ${\Delta}$ and R dark field TEM images we show that the phase transition proceeds by a loss of coherence of TiO6 octahedral tilting along the c-axis, leading to a microstructure of thin nanoscale platelets with a different local symmetry to the macroscopic structure. These persist well above the phase transition temperature and are probably responsible for the long-standing discrepancy between Raman spectroscopy and diffraction measurements in this materials system, as well as other secondary effects.

A Hubbard-Holstein dimer functions as a correlation-driven quantum battery, with ergotropy robustly stored, under some conditions, even in the presence of dissipation. We find that, although optimal work extraction can in principle recover all the stored energy, it requires unrealistically fine-tuned couplings. By contrast, a physically realizable protocol based on spectral matching between the battery and the load achieves substantial, albeit suboptimal, energy extraction. Our results identify a mechanism for quantum energy storage, provide a realistic route to work extraction that is amenable to machine-learning-based theoretical exploration, and suggest that quantum batteries may not be universally deployable: the microscopic mechanism responsible for storing energy can constrain the classes of systems able to efficiently extract it.

Dislocation loops govern the properties of crystalline materials, but extracting their detailed characteristics from atomistic simulations is difficult when loops are fragmented or embedded in compact defect debris. We present Savi-Bhransha, a graph-theoretic method that reconstructs interstitial and vacancy loops directly from local defect-displacement motifs, without constructing a global interface mesh. The method identifies Burgers-vector family, habit plane, loop size, segment-wise edge/screw character, and boundary and bulk defect populations for BCC, FCC, and HCP crystals. We apply it to single-cascade simulations over a range of energies in BCC W and HCP Zr, and to successive collision cascades in BCC W and FCC FeNiCr. We benchmark the method against the Dislocation Extraction Algorithm (DXA). Total dislocation lengths remain strongly correlated between the two methods, while Savi-Bhransha returns more stable loop-level objects in complex environments where DXA returns fragmented, overlapping open segments. Savi-Bhransha also better resolves mixed-morphology defects and dislocations near other defects, including vacancy clusters. Median runtime speedups are 6.34x for BCC W and 8.86x for HCP Zr, with peak-memory reductions up to 7.77x. In successive W cascades, the resolved boundary-defect concentration brackets transient-grating-spectroscopy measurements and the predicted Burgers-vector fraction agrees with room-temperature TEM. In FCC FeNiCr, the method resolves Heidenreich-Shockley dissociation, with a Shockley-pair signature in about 91% of surviving <110>-family interstitial clusters. Savi-Bhransha therefore enables efficient, topology-resolved analysis of large radiation-damage simulations and direct comparison with experimentally accessible observables.

Tunneling of ultracold bosons confined in a one-dimensional optical lattice results in a nontrivial gauge field depending on density-difference between the sites involved. The density dependent tunneling (DDT) causes a first-order quantum phase transition from the Bose-Einstein condensate to the localized soliton. Here, we examine the low-lying quasiparticle mode evolution across the transition in the weakly-interacting limit. To this end, we employ the discrete Bogoliubov theory and dispersion curves to reveal an increase in the quasiparticle energies of dipole (and higher) excitations with DDT in the soliton phase while preserving the zero-energy mode. This is due to the decrease in effective tunneling, resulting in a larger energy cost to move the soliton, and causes faster dipole oscillations. The repulsive on-site atomic interaction further shifts the critical gauge field of DDT to a larger value by stabilizing the lattice soliton. The latter is corroborated by a phase diagram in the complex gauge field plane and mode energy gap of quasiparticles. We further show that the soliton does not exhibit Bloch oscillations as the effective momentum becomes density-dependent and deforms its internal structure. The dynamical response of the trap quench does not excite the width of localized wave-packet, and the breathing oscillations are suppressed. The latter two dynamical properties of the condensate uniquely contrast the soliton state due to the density-dependent gauge field.

High-kinetic-inductance (HKI) transmission lines provide a promising platform for compact nonlinear superconducting microwave devices. Existing theoretical descriptions are typically based on the slowly varying envelope approximation, which becomes inadequate for strongly nonlinear resonant structures with pronounced spatial field variations. Here, we develop a theoretical framework for single-frequency nonlinear wave propagation in HKI transmission lines by formulating the problem as a boundary value problem that retains the full spatial dependence of the electromagnetic fields. Applying the method to resonant transmission-line geometries, we demonstrate power-dependent resonance shifts, bistable transmission solutions, and strongly direction-dependent transport arising from asymmetric impedance barriers, yielding transmission contrasts of up to $93\%$ without magnetic bias fields. The framework is further extended to a three-port stub geometry, where nonlinear interference produces shifted anti-resonances and Duffing-like spectral distortions. Our approach provides a versatile tool for the analysis and design of strongly nonlinear superconducting microwave devices.

We examine a one-dimensional binary mixture of ultradilute quantum droplets in the presence of a central potential defect. The properties of the potential strength and the number of atoms exhibit distinct polarization transitions and low-lying ollective excitation spectra. The balance of (attractive) Lee-Huang-Yang quantum fluctuations and repulsive mean-field interactions results in a self-bound quantum droplet in a potential well. However, the potential barrier causes the polarization transition with the number of atoms, which is reflected in the excitation spectrum as a discontinuity and softening of the quasiparticle modes. We reveal that the critical number of atoms for the transition decreases as the attractive intercomponent interaction increases. Finally, the quench time dynamics of the interaction in potential barrier and well show the localization and diffusive fragmented droplets of two-component systems.

Integrating few-layer materials into photonic circuits is a promising concept for novel on-chip photonic applications. We incorporate transition metal dichalcogenides (TMDs) with femtosecond-laser-written surface waveguides, which are embedded in fused silica chips. Our novel low-temperature optical spectroscopy setup enables coupling to the waveguide and simultaneous focus from the top to the TMD layer for a distinct excitation and collection of micro-photoluminescence ($\mu$PL) signals in several measurement geometries. Along these lines, we observe spectral changes of the A exciton for encapsulated TMD monolayers when capturing the $\mu$PL signal propagating through the waveguide. Depending on the thickness of the encapsulation with hexagonal boron nitride (hBN), these changes manifest as energetic redshifts of the A exciton, or even a splitting of the A exciton into two components. We attribute this behavior to strong coupling of the waveguide mode and the exciton in the sample, giving rise to the formation of propagating exciton-polaritons. Our interpretation is supported by calculations for a simplified model of a slab waveguide in the vicinity of an exciton by using the transfer matrix method. Having proven to be a highly adaptable framework for the study of propagating polaritons, our experimental platform likewise holds great promise for harnessing the unique properties of exciton-polaristons in integrated photonic circuits.

The stress analysis of a three-dimensional elastic hollow sphere subjected to uniaxial compression is revisited, employing an elastodynamic framework. Through the application of the Laplace transform, the scalar and vector potentials of displacement are expanded, facilitating a detailed exploration of the system's mechanical behavior. The static solutions for displacement and stress distributions are derived in the long-time limit, which reveal key insights into the response of the elastic hollow sphere. Notably, on the inner surface, certain quantities exhibit a peak at the point where the angle between the compressive force and the point on the surface becomes perpendicular, indicating localized stress concentration. These findings provide a robust analytical approach for understanding and predicting the behavior of elastic hollow spheres under uniaxial loading, with implications for material science and structural engineering.

Understanding how chemically induced surface transport generates fluid motion in confined geometries is essential for the rational design of microscale pumping devices and active microfluidic systems. Here we develop a theoretical framework for chemically driven phoretic flows in a three-dimensional wedge geometry in the diffusion-dominated regime. We formulate both the diffusion and hydrodynamic problems using a Fourier-Kontorovich-Lebedev spectral representation, exploiting the translational invariance and radial structure of the wedge. Green's functions for the concentration field are derived for reflecting and mixed reflecting-absorbing boundaries, reducing to finite image-like sums or closed-form expressions for commensurate wedge angles. The resulting slip velocity is then used to construct the three-dimensional Stokes flow through the Papkovich-Neuber representation, yielding explicit spectral solutions for the velocity field. These results establish a Green's-function framework for phoretic pumping in wedge-shaped confinement and provide analytical benchmarks for numerical simulations of chemically driven transport in confined microfluidic systems.

An octahedral network has been widely used as a fundamental building block for diverse architected materials. Here, we demonstrate that heterogeneous octahedral materials can achieve complete elastic isotropy at a critical constituent volume fraction, nearly independent of the constituent stiffness ratio. The anisotropy ratio, a, transitions from a > 1 to a < 1 at the critical constituent volume fraction, due to a change in the dominant deformation modes. Microstructural analysis reveals that the geometry and connectivity of the heterogeneous octahedral materials are very similar to those of heterogeneous materials constructed on combined simple cubic (SC) and body-centered cubic (BCC) lattices exhibiting opposite elastic anisotropy. More importantly, we demonstrate that varying the constituent volume fractions in the octahedral materials governs elastic anisotropy, similarly to tuning the BCC-to-SC composition ratio in the SC-BCC materials widely employed for designing mechanically isotropic architected materials. The mechanical isotropy of the heterogeneous octahedral materials is further assessed using 3D-printed prototypes.

Predicting the extrinsic properties from hysteresis loops of a magnetic grain, namely the coercive field, remanent magnetisation, and maximum energy product, from its intrinsic micromagnetic parameters is a central problem in permanent-magnet modelling. Established analytical models provide useful estimates but often neglect nonuniform magnetisation processes, whereas direct micromagnetic simulations are computationally expensive. In this work, we train machine-learning models on 12012 micromagnetic simulations of an idealised cubic grain, spanning broad ranges of the saturation magnetisation, exchange constant, and uniaxial anisotropy constant. Benchmarked against the analytical models on identical held-out data, the machine-learning models predict all three extrinsic properties with substantially lower errors. Symbolic regression recovers the Kronmüller form of the coercive field, with an effective demagnetising factor that depends on the material, and finds new closed-form expressions for the remanence and maximum energy product. Each law contains at most two fitted constants yet approaches the accuracy of the machine-learning models. We also investigate the inverse problem of recovering the intrinsic parameters from the three extrinsic properties. The saturation magnetisation and anisotropy constant are recovered accurately, whereas the exchange constant is not, because it influences the extrinsic properties only weakly. The trained models are released through the mammos-ai Python package, enabling thousands of candidate parameter sets to be screened in seconds rather than the hours or days required by direct micromagnetic simulation.

Statistical validation of projected bipartite networks depends critically on the null model adopted to describe random co-occurrences. Although several null models have been proposed, their comparison has mainly focused on the validated backbones they produce rather than on the statistical assumptions underlying their construction. Here we compare four widely used null models - the microcanonical configuration model generated by the Curveball algorithm, the Bipartite Configuration Model (BiCM), the Bipartite Partial Configuration Model (BiPCM), and the Hypergeometric approximation - using three empirical bipartite systems from comparative genomics, international trade and food science. We use the statistically validated links obtained from the microcanonical bipartite configuration model as the reference benchmark for assessing performances of the other three models. Our central result is that the statistical consequences of relaxing null-model constraints cannot be understood solely from the constraints themselves but must be analyzed through the probability distribution induced for the co-occurrence statistic. In particular, the combined behaviour of the expectation and variance largely explains the observed differences among the statistically validated backbones. We further derive a leading-order sparse approximation for the BiCM expectation, showing that the first correction to the Hypergeometric prediction is controlled by the degree heterogeneity of the non-projected layer. Surprisingly, despite neglecting this heterogeneity, the Hypergeometric model accurately reproduces the co-occurrence variance of the microcanonical ensemble across all datasets. Our results suggest that null models should be compared not only according to the constraints they preserve but also according to the statistical consequences that these constraints induce on the distribution of the test statistic.

We develop a model for the diffusiophoresis of a chemically inert, rigid spherical colloid with fixed surface charge in a monovalent weak electrolyte, in which a neutral solute reversibly dissociates into ions. A weak far-field gradient is imposed in the neutral-species concentration. In the fast-reaction limit, local mass action and bulk electroneutrality determine the far-field ionic gradients, while the bulk zero-current condition determines the diffusion-potential gradient. We solve the coupled Nernst-Planck, Poisson and Stokes equations for arbitrary double-layer thickness, linearising in the gradient strength while retaining the nonlinear Poisson-Boltzmann equilibrium. In the Debye-Hückel limit, the mobility consists of one half of the matched fully dissociated response and a finite-double-layer correction due to neutral-ion coupling; the correction vanishes in both the Hückel and Smoluchowski limits. Beyond this limit, numerical solutions for the representative systems reveal a branch-selective response as the surface potential magnitude increases. When the counterion is slower than the co-ion, dissociation-association weakens a retarding concentration-polarisation layer, allowing the mobility to exceed the fully dissociated value. When the counterion is faster, the response remains close to the one-half scaling set by mass action. This reaction-polarisation coupling cannot be reproduced by adjusting only the bulk ionic strength, and hence the Debye length, in a fully dissociated model.

Designing nonlinear piezoelectricity requires suppressing the linear piezoelectric coefficient without extinguishing higher-order electromechanical response, yet a general and reconfigurable route remains lacking. Here we introduce stacking-engineered piezoelectric interference as such a mechanism in multilayer sliding ferroelectrics. Combining first-principles calculations with a generalized Ginzburg–Landau framework, we show that each interlayer gap acts as a local piezoelectric channel whose sign and magnitude are determined by stacking. Constructive interference between same-signed channels produces a linear-dominated response, whereas destructive interference between oppositely signed channels suppresses the linear coefficient while preserving a finite quadratic response. Representative MoS$_2$ and NiTe$_2$ multilayers approach the parabolic limit, with BAAC-stacked MoS$_2$ reducing the linear-to-quadratic crossover strain by a factor of 25 relative to CBA-stacked MoS$_2$. Experimentally accessible tetralayer MoS$_2$ sliding pathways further connect linear-dominated, quadratic-dominated and sign-inverted states. Here, we identify stacking-engineered interference as a design principle for programmable nonlinear electromechanics in layered materials.

Alignment of anisotropic particles strongly governs the functional properties of printed materials, yet most studies have focused on particle alignment in single evaporating droplets. In droplet- based printing, however, neighboring droplets can coalesce, generating rapid capillary flows that redistribute material and markedly affect the final morphology. Here, we use mesoscale simulations to investigate how droplet coalescence and subsequent evaporation jointly determine alignment and redistribution in sessile droplets with different contact angles and volumes. During the early stages of coalescence, the mean nematic order along the coalescence direction increases for all combinations of contact-angle and volume asymmetries of the droplets. At later times, the mean nematic order either continues to increase or decreases, depending on the droplet geometry. We derive a geometric scaling based on curvature and volume asymmetry and show that the simulation results collapse onto a master curve, identifying an effective geometric asymmetry parameter that governs the mean nematic order at the end of coalescence. During evaporation, the contact angle strongly influences how the coalescence-induced orientational structure is transferred to the final deposit. For small contact angles, the contact line remains pinned for a longer duration, better preserving alignment. In contrast, larger contact angles promote contact-line motion, which weakens alignment, as reflected by a reduced mean nematic order, while simultaneously generating stronger concentration gradients in the final deposit.

We study a continuum Schrödinger particle on a surface of constant curvature subject to a radial random potential and a weaker angle-dependent perturbation. Exact angular-momentum decomposition reduces the rotationally symmetric problem to independent one-dimensional random radial channels. A positive radial Lyapunov exponent distinguishes radial Anderson localization from the circular probability profile imposed by symmetry. Projection of a narrow radial mode produces a disordered one-dimensional ring. For angular disorder that is stationary in physical arc length, the ring localization length grows as the inverse square of the perturbation amplitude. Equating this length with the geodesic circumference yields a shell-breaking radius that grows algebraically in flat space but as $2a\ln(1/\varepsilon)+O(1)$ on a hyperbolic surface of curvature radius $a$ and angular-disorder amplitude $\varepsilon$. Transfer-matrix and finite-ring calculations determine the crossover coefficient. Direct polar-grid calculations at the same angular energy as the ring model use unbiased tracking of the degenerate angular-momentum subspace across six independent radial-disorder realizations and quantify the validity of the single-mode projection. The noncommuting weak-disorder and flat-curvature limits establish a curvature-amplified crossover for this deliberately anisotropic disorder ensemble, rather than a generic metal–insulator transition on the hyperbolic plane.

We investigate electronic transport through a doped quantum well strongly interacting with a photonic mode confined in a double-metal cavity. Using a nonequilibrium Green's function formalism, we derive compact expressions for the current valid for arbitrary collective light–matter coupling strengths exceeding the relevant loss rates. We show that cavity polaritons leave observable transport signatures when the carrier injection rate is smaller than the cavity-induced electronic broadening. In this regime, the current–voltage characteristics exhibit inelastic sidebands associated with resonant and anti-resonant polariton emission, which are strongly enhanced under resonant illumination. Our results provide a realistic route to detecting cavity-induced modifications of charge transport in semiconductor heterostructures.

We compare two Ruppeiner metrics constructed under fixed volume and fixed particle number conditions ($g_{_V}$ and $g_{_V}$) by analyzing the scalar curvature $R$ and introducing the scalar curvature density $\mathcal{R} = \sqrt{|g|}\,R$ as a complementary geometric invariant. Three fluid models of increasing physical realism are considered: van der Waals, Lennard-Jones, and argon described by a multiparameter equation of state that correctly reproduces non-mean-field critical behavior consistent with the Ising universality class. We find that $R$ and $\mathcal{R}$ exhibit distinct critical scaling: $R \sim t^{-d\nu}$ is governed by the correlation length exponent, whereas $\mathcal{R} \sim t^{-(1+\beta)}$ scales solely with the order parameter exponent $\beta$, a result that follows analytically from hyperscaling and the Rushbrooke relation independently of the universality class. The $N$-metric consistently outperforms the $V$-metric in reconstructing the vapor-liquid coexistence curve away from criticality, and the four Widom lines defined by the minima of $R_{_V}$, $R_{_N}$, $\mathcal{R}_{_V}$, and $\mathcal{R}_{_N}$ display a characteristic fourfold structure reproduced across all three models. The loci where both representations yield identical geometric descriptions define two new objects: the Curvature Equality Curve (CEC, $R_{_V} = R_{_N}$) and the Curvature-Density Equality Curve (CDEC, $\mathcal{R}_{_V} = \mathcal{R}_{_N}$), with the CDEC enclosing a substantially larger region of the phase diagram in all cases. These results establish $\mathcal{R}$ as a meaningful complement to $R$ in thermodynamic geometry and highlight the nontrivial role of metric choice in the description of phase transitions and supercritical behavior.

The interplay of strongly localized 4$f$ electrons with itinerant spd-valence states gives rise to a wide range of correlated phenomena and properties that place lanthanide materials at the focus of considerable research efforts. Beyond the bulk, their surfaces are of particular interest, where the reduced coordination, a modified crystal electric field, broken inversion symmetry in combination with strong spin-orbit coupling, and the emergence of surface states and resonances considerably reshape 4$f$-driven electronic and magnetic properties. This, in turn, enables novel functionalities of particular relevance for low-dimensional systems and their applications. This review summarizes how advances in photoelectron spectroscopies, together with improved crystal growth, have enabled detailed insights into bulk and surface phenomena of lanthanide-based crystals. After a brief overview of key developments from the 1970s to the 1990s, we discuss recent progress, focusing on systematic studies by the authors and collaborators that form a coherent line of research. These include the unveiling of $k$-resolved $f-spd$ hybridization, the formation and evolution with temperature of $f$-derived Fermi surface in Kondo lattices, layer-dependent 4$f$ magnetic anisotropy, the emergence of ferromagnetically ordered surfaces in systems with non-magnetic bulk ground state. This coherent line of research addresses core questions in the physics of 4$f$ systems and opens opportunities for engineering novel lanthanide-based architectures, including heterostructures and supramolecular complexes with novel physical properties and functionalities.

Phase-field approaches to fracture, initially designed as regularization of the Griffith model of brittle fracture, are now commonly viewed as gradient-damage models whose regularization length becomes a material property driving crack nucleation. One weakness of this approach is that the strength surface cannot be arbitrary: its shape is dictated by the elastic energy, and its magnitude by the regularization length. We focus on the antiplane version of the model introduced by Bourdin, Marigo, Maurini and Zolesi (arXiv:2506.22558), which handles crack propagation along unknown paths and nucleation governed by an arbitrary convex strength surface by degrading the strength instead of the stiffness. It can be interpreted as a regularization of softening plasticity in which localization bands obey an equivalent cohesive law set by the strength domain and the toughness, while the role of the regularization length, when small compared to the elasto-cohesive length, is purely numerical. Strength, stiffness, and toughness thus become independent material data, and limit analysis, perfect plasticity, cohesive fracture, and brittle fracture merge into a single variational framework. We derive closed-form solutions for a simple shear problem, propose a numerical scheme combining alternate minimization and conic programming, and numerically verify the equivalent cohesive law, its independence of the regularization, and the size effect governed by the elasto-cohesive length. A "surfing" simulation highlights the structure of the propagating crack while a re-entrant V-notch is used to show how the model bridges small-scale yielding, cohesive fracture, and brittle fracture without a priori hypotheses.

Silicon-on-insulator technology is widely used to fabricate silicon based devices, from advanced transistors to photonic circuits or nanomechanical systems. Integrating low loss superconducting quantum circuits with silicon-on-insulator substrates enables to couple the advantages offered by the mature silicon technology to the exquisite sensitivity of superconducting circuits. The natural approach, inherited from research in superconducting microwave devices, is to use a substrate made with highly resistive silicon, known for its low level of microwave losses. In this work, using superconducting microwave resonators, we show that counterintuitively, standard resistivity silicon-on-insulator substrates perform better than high resistivity silicon-on-insulator substrates at cryogenic temperatures. In the latter case, the presence of a parasitic sheet conduction at the interface between bulk silicon and silicon oxide acts as the dominant loss mechanism. This parasitic sheet can be suppressed using substrates with intentionally induced traps. In such substrates, losses are ultimately limited by the dielectric losses of the silicon oxide layer. These substrates offer interesting perspectives for the development of superconducting nanoelectromechanical systems. First, the release, i.e. the removal of the silicon oxide, could be limited to the moving parts, thereby maintaining the mechanical integrity of the rest of the device. Additionally, such structure would enhance heat evacuation into the bulk of the substrate which is an issue in current devices such as microwave-to-optics converters.

Hybrid heterostructures combining two-dimensional semiconductors with ferroelectric materials offer a versatile route to actively control light-matter interactions at the nanoscale. Here, we report all-optical, light-induced domain-selective control of second-harmonic generation (SHG) in monolayer molybdenum disulfide (MoS$_2$) integrated with periodically poled lithium niobate (LiNbO$_3$). Spatially resolved SHG imaging reveals a pronounced modulation of the nonlinear optical response of monolayer MoS$_2$ governed by the ferroelectric domain pattern of the underlying substrate. A strong SHG contrast is observed between domains of opposite polarization, with a marked dependence on both the excitation wavelength and the incident optical power. The comparison between ferroelectric domains that either enable or do not exhibit light-driven photodoping in the MoS$_2$ monolayer provides a direct assessment of the role of carrier density in the nonlinear optical response. We find that ferroelectric-polarization-controlled photodoping at the MoS$_2$/LiNbO$_3$ interface enhances the effective second-order susceptibility, $\chi^2$, producing an increase in SHG intensity of up to ~70% under resonant excitation conditions. Ab initio calculations corroborate that charge doping modifies the electronic band structure of MoS$_2$ and strongly affects $\chi^2$ in the resonant regime, providing microscopic support for the experimentally observed modulation. The results highlight the combination of light intensity and ferroelectricity as a powerful knob for band-structure modulation in 2D materials and reconfigurable nonlinear optical responses, opening pathways toward programmable frequency conversion, smart light modulators, and advanced nonlinear photonic functionalities in integrated hybrid platforms.