Papers

We map the phase diagram of a two-mode atom-molecule Bose-Einstein condensate with Fano-Feshbach and coherent three-body recombination (cTBR) terms. The standard second order phase transition observed as the molecular energy is tuned through the Feshbach resonance, is replaced by a first order transition when cTBR becomes prominent, due to a double-well structure in the free energy landscape. This transition is associated with atom-molecule entanglement, bistability, and molecular metastability. Our results establish cTBR as a powerful knob for quantum state engineering and control of reaction dynamics in ultracold chemistry.

We have experimentally investigated the magnetocaloric effect (MCE) of a prototype spin-frustrated one-dimensional spin-chain system, the famous Haldane-chain system, R2BaNiO5 (R = Nd, Gd, Er, Dy). The significant MCE is observed far above long-range ordering, even in the paramagnetic region, which is attributed to the change in magnetic entropy due to short-range spin correlation arising from (low-dimensional) magnetic frustration. Such a spin-chain incipient MCE above long-range ordering is rarely reported. Interestingly, multiple magnetocaloric switching from conventional to inverse MCE (and vice versa) are observed below long-range magnetic ordering, as a function of temperature and magnetic field, for the R = Nd, Dy, and Er members. However, such MCE switching is absent in the Gd member, which is an S-state atom (orbital moment L = 0). Our systematic investigation of this series demonstrates that the interplay between crystal-electric field (CEF), strong spin-orbit coupling (SOC) and rare earth anisotropy of R-ions play an important role in spin reorientation, leading to multiple MCE switching due to intriguing changes in magnetic and lattice entropy. The maximum change of entropy for Er, Gd, Dy and Nd is 7.8, 6.8, 4.0 and 1.0 J Kg-1 K-1 respectively. Our study presents a pathway for tuning MCE switching and the MCE effect over large temperature regions in d-f coupled spin-frustrated and spin-chain oxide systems.

The Lanczos recursion maps operator growth onto the motion of a wave function on a semi-infinite chain, and for linearly growing Lanczos coefficients the deep region of the chain behaves like the near-horizon region of a black hole. We develop this correspondence in the time domain and determine how far it extends. Writing the Krylov equation as an exactly skew-adjoint difference operator, we derive a unitary continuum limit whose corrections are suppressed by $n^{-2}$ once the origin of the chain is fixed by the offset of the Lanczos coefficients. For $b_n\simeq\alpha n$ the Krylov evolution is chiral transport in $\ln n$, which coincides with infalling waves near the horizon of an AdS$_2$ black hole when the Krylov depth is identified with the blueshift of an infalling particle; this fixes $\alpha=\pi T$, while staggered configurations of the chain carry the outgoing chirality. For $b_n=\alpha\sqrt{n(n+2h-1)}$ the correspondence is exact: the Krylov basis is the discrete series of $\mathrm{SL}(2,\mathbb{R})$ carried by a bulk scalar of mass $m^2L^2=h(h-1)$, the Liouvillian is the boost generator of the black hole at temperature $T=\alpha/\pi$, and positivity of $b_n^2$ reproduces the Breitenlohner–Freedman bound, saturated by strictly linear coefficients. Beyond leading order we prove that, for every Lanczos sequence with a smooth large-$n$ expansion, the ingoing solutions of the Krylov equation have coefficients polynomial in frequency to all orders in $1/n$, whereas a massive bulk field has a pole at the first special point $\omega=-2\pi iT$ with residue proportional to $m^2$. Smooth subleading Lanczos data therefore cannot encode the bulk mass locally. The obstruction persists for the BTZ black hole, for which we obtain the Lanczos coefficients in closed form.

By coupling Bardeen-Cooper-Schrieffer (BCS) theory with isolated bands to an external gravitomagnetic vector potential via a gravitomagnetic Peierls substitution, we identify a quantum-geometric contribution to the electronic contribution of the thermal conductivity. This contribution is governed by the quantum metric in the parameter space spanned by the components of the external gravitomagnetic vector potential which corresponds to a weighted quantum metric in momentum space. In the flat-band limit, we establish an upper and lower Wiedemann-Franz-type bound for the ratio of thermal Meissner stiffness and electric Meissner stiffness (superfluid weight), whose prefactors are provided by the extrema of the squared energy offsets of the outer single-particle bands of the system. Similarly to the superfluid weight, this also leads to a lower bound of the thermal Meissner stiffness in terms of the Chern number. Our results apply to both superconductors and other fermionic superfluids.

Thermodynamics coupled quantum features on electron and hole dynamics in Dirac materials is quite interesting and crucial for real device applications such as electronic, thermoelectric, energy devices, and quantum circuits. The correlation between the formation of electron-hole puddles near the charge neutrality point (CNP) and the role of disorder in terms of differential entropy is fundamentally important for the Dirac transport mechanism in graphene systems, but not yet well-established. With this motivation, we map the energy quantization for Dirac materials through the empirical relation of voltage-driven charge density in monolayer graphene, using the differential entropy (h)-ruled wavevector (k) mechanics. For this work, we propose the four postulates which are the key observable descriptions of earlier research reports, to study the precise electronic transport via an entropy-guided wavevector propagation approach, along with the Klein paradox, which pertains to the ultrafast dynamics in the Dirac or quasi-Dirac systems. The introduced h-ruled k and h-ruled N relations generalize the electron dynamics in both the unbounded and potentially bounded Dirac systems. Through the quantization mapping procedure under different voltage-driven potential (U=eV) boundary conditions, the observed energy shift from lower to excited quantum state obeys the relation of N(k)=N(U)^3; here, N(U) is the voltage-driven potential energy contribution factor for the quantum state existence. In such a way, the mapped electron density, diffusion coefficient, and mobility for bounded Dirac materials are increased by orders of N^3, N^2, and N, respectively. This study reveals information about the interaction potential-DOS relationship in the Dirac materials.

The non-relativistic spin-momentum locking in altermagnets gives rise to a time-reversal-odd spin Hall effect, known as the altermagnetic spin-splitting effect (ASSE). Although ASSE was first reported in RuO$_2$, subsequent experiments have yielded inconsistent results, leaving its spin-transport mechanism unclear. Here, we systematically investigate how strain, crystal orientation, and the Hubbard $U$ parameter influence the magnetic ground state and spin Hall response of RuO$_2$. Guided by recent experimental observations, we find that $U$ is likely smaller than the value required to induce intrinsic magnetism, suggesting that bulk RuO$_2$ and (001)/(101) RuO$_2$ thin films grown on TiO$_2$ are nonmagnetic in the absence of extrinsic effects. In contrast, (100) and (110) films exhibit strain-induced altermagnetic spin splitting, leading to a strong ASSE even without Hubbard $U$ corrections. These results reconcile previous experimental discrepancies and provide design guidelines for RuO$_2$-based spintronic devices.

We present a collaboration ring model – a network of players playing the prisoner's dilemma game and collaborating among the nearest neighbours by forming coalitions. The microscopic stochastic updating of the players' strategies are driven by their innate nature of seeking selfish gains and shared intentionality. Cooperation emerges in such a structured population through non-equilibrium phase transitions driven by propensity of the players to collaborate and by the benefit that a cooperator generates. The robust results are qualitatively independent of number of neighbours and collaborators.

Quantum spin rings represent fundamental model systems that exhibit distinctive quantum phenomena-such as quantum critical behavior and quasiparticle excitations-arising from their periodic boundary conditions and enhanced quantum fluctuations. Here, we report the on-surface synthesis and atomic-scale characterization of antiferromagnetic S=1/2 quantum spin rings composed of pristine and unmodified [2]triangulene units on a Au(111) surface. Using stepwise on-surface synthesis followed by STM tip-induced dehydrogenation, we precisely constructed cyclic five- and six-membered spin rings and investigated their spin states via scanning probe microscopy and multireference calculations. Nc-AFM imaging reveals that the six-membered ring retains a planar geometry, whereas the five-membered ring exhibits pronounced structural distortion. The six-membered ring hosts a uniform excitation gap that can be accurately described by a Heisenberg spin model and multireference CASCI calculations. In contrast, the distorted five-membered ring displays spin ground states with asymmetric spatial distributions due to degeneracy lifting induced by structural distortion. Our findings establish a versatile molecular platform for exploring correlated magnetism and quantum spin phenomena in cyclic organic magnetic architectures with disorder.

Motivated by the recent experimental discovery of the $T$-linear specific heat in pressurized and magnetized Shastry-Sutherland Mott insulator SrCu$_2$(BO$_3$)$_2$, we perform the state-of-the-art thermal tensor-network computation on the Shastry-Sutherland model under a magnetic field. Our simulation results suggest the existence of a symmetric intermediate phase with $T$-linear specific heat at low temperature, occupying a large parameter space and between the plaquette-singlet phase and antiferromagnetic phase at low fields and other symmetry-breaking phases at high fields before the system is fully polarized. Such an unexpected novel state bears an astonishing similarity to the experimental findings in the material. It opens the door to further investigations of the possible liberation of deconfined magnetized Dirac spinons by the competing interactions in this highly frustrated quantum magnet model, and by the combined effects of magnetic field and pressure in the associated Shastry-Sutherland Mott insulator SrCu$_2$(BO$_3$)$_2$.

The layered transition metal dichalcogenide, TaSe2, exhibits rich electronic phenomena across its polymorphs, 1T, 2H, and 3R, largely driven by differences in atomic coordination and c-axis stacking. In the 1T phase, octahedral coordination and AA stacking promote strong interlayer coupling and stabilize a commensurate charge density wave (CDW) with star-of-David clusters that set in at high temperatures. The 2H phase exhibits trigonal prismatic coordination with AB stacking, and hosts both incommensurate and commensurate CDW phases and weak superconductivity at very low temperatures. The 3R phase, characterized by ABC stacking and trigonal prismatic coordination, exhibits enhanced superconductivity along with CDW order, attributed to modified interlayer hybridization and reduced CDW competition. These stacking-dependent variations in interlayer coupling are critical in tuning correlated states in the dichalcogenides.

Cation-disordered solids offer a rich chemical landscape where local coordination, lattice responses, and configurational disorder collectively, yet often implicitly, govern ion transport. In cation-disordered rocksalt oxides, Li+ diffusion has conventionally been rationalized by the static 0-transition-metal (0-TM) percolation rule, which assumes an ideal, passive lattice and thus fails to capture experimentally accessible capacities. Here, we show that lattice distortion is an essential, previously overlooked degree of freedom that actively reshapes Li+ percolation networks. By developing a lattice-responsive framework combining Monte Carlo sampling of cation configurations with machine-learning-accelerated molecular dynamics, we quantitatively predict Li+ percolation and electrochemical capacities within 5% of experiment. Our results reveal a causal coupling between lattice distortion and cation short-range order: enhanced local distortions precede and suppress short-range ordering, activating Li+ migration through nominally inaccessible 1-TM channels, fundamentally extending percolation beyond the 0-TM paradigm. Guided by this, we design and synthesize a high-entropy oxide, Li1.2Mn0.2Ti0.2V0.2Mo0.2O2, which exhibits enhanced distortion and achieves a 71.9% Li+ percolation network, surpassing 65.8% in Li1.2Mn0.4Ti0.4O2, delivering 256.3 mAh/g capacity, closely matching our prediction of 255.1 mAh/g. These findings establish lattice distortion as an active control parameter for ion transport, revising percolation concepts and offering a general design principle beyond metal-ion cathodes.

Gold in crystalline compounds is typically only stable in oxidation states Au1+ and Au3+. Even compounds with nominal Au2+ usually disproportionate into Au1+ and Au3+. Recently, Cs4Au3Cl12 was synthesized, where gold took the 2+ state in the bulk. Here, we investigate this compound using first-principles calculations and show that stabilization of the Au2+ ion is through the formation of a polaron crystal. The electronic and phononic structure suggest that the bonding network can be interpreted as a collection of [Au2+Cl4]2- and [Au3+Cl4]1- square planar motifs, and the crystal lacks a smooth pathway for Au2+ to disproportionate into Au1+ and Au3+ without creating dangling bonds. The electronic states of Au are contained within each AuCl4 motif, which allows for the Au2+ state to be localized and isolated electronically. The Au2+-sites form an ordered structure, which is driven by a strong repulsive interaction between [Au2+Cl4]2- motifs due to their lattice distortion. By considering redox reaction, we show that Cs4Au3Cl12 has the maximal density of Au2+, and further reduction will induce a delocalized state. Cs4Au3Cl12 has distinctive electronic structure, with a narrow gap, isolated HOMO and LUMO bands strongly localized at the Au-sites, and magnetization at the Au2+-sites making Cs4Au3Cl12 unique among quantum materials. Cs4Au3Cl12 can be a testbed to explore novel gold chemistry, opening opportunities to control oxidation state through engineering of lattice distortions.

We present a comprehensive first-principles investigation of the structural, electronic, vibrational, and superconducting properties of halogen-functionalized Mo2YX2 (Y = C, N; X = F, Cl, Br, I) MXene monolayers. Density functional theory and density functional perturbation theory calculations reveal that, among the halogenated systems considered, only Br- and I-functionalized Mo2C monolayers are dynamically stable, as confirmed by positive definite phonon spectra throughout the Brillouin zone. Electronic structure calculations show metallic behavior with states near the Fermi level dominated by Mo d orbitals with pronounced electronic density of states, providing favorable conditions for strong electron-phonon coupling (EPC). The resulting EPC constants place both systems in the strong coupling regime, yielding superconducting transition temperatures of Tc = 13.1 K for Mo2CBr2 and Tc = 18.1 K for Mo2CI2 within the Allen-Dynes formalism. Notably, halogen functionalization itself plays a crucial role in enhancing superconductivity in Mo2C, which has Tc = 7.2 K, leading to a substantial increase in the superconducting transition temperature compared with pristine Mo2C through strengthened electron-phonon coupling. Furthermore, we demonstrate that superconductivity in these systems is highly tunable via carrier doping and biaxial tensile strain. Electron doping significantly enhances EPC and raises Tc up to 21.7 K for Mo2CBr2 and 21.3 K for Mo2CI2. Our results identify halogen-functionalized Mo2C MXenes as mechanically robust, phonon mediated two dimensional superconductors and highlight carrier doping as an effective strategy for optimizing their superconducting performance.

Machine Learning Interatomic Potentials (MLIPs) are a modern computational method that allows achieving near-quantum mechanical accuracy (DFT) while still describing large-scale systems in molecular dynamics (MD) simulations. In this work, we use MLIP from DeepMD package and the classical Tersoff potential for SiC (Tersoff.SiC potential) to fully and accurately describe atomic interactions and apply them to molecular dynamics simulations of penta silicene sheet. The results show that the melting points (T$_g$) temperatures of the system in the canonical NVT and isobaric NPT sets are 632 K and 606 K, while the Tersoff.SiC potential have the high melting points, respectively. In addition, the radial distribution function exhibits characteristic peaks at interatomic distances of 2.275 Å \text{} and 2.375 Å, while the Tersoff.SiC potential only describe distance of 2.375 Å. Furthermore, penta silicene was also simulated using on-the-fly machine learning for 10 ps to evaluate the structural stability of the system. This study investigates the thermodynamic properties of two-dimensional penta silicene sheets with pentagonal structures using a high-precision, cost-effective method, contributing further evidence to support experimental synthesis and opening up potential future applications of this material.

Amontons' law postulates a monotonic relationship between frictional force and the normal load applied to a sliding contact. This empirical rule, however, fails in systems where internal degrees of freedom - such as structural or electronic order - play a central role. Here, we demonstrate that friction can emerge entirely from magnetically driven configurational dynamics in the absence of physical contact. Using a two-dimensional array of rotatable magnetic dipoles sliding over a commensurate magnetic substrate, we observe a pronounced non-monotonic dependence of friction on the interlayer separation, and thus on the effective load. The friction peaks at an intermediate distance where competing ferromagnetic and antiferromagnetic interactions induce dynamical frustration and hysteretic torque cycles during sliding. Molecular dynamics simulations and a simplified two-sublattice model confirm that energy dissipation is governed by collective magnetic reorientations and their hysteresis. Our results establish the occurrence of sliding-induced changes in collective magnetic order, which has a strong impact on friction, and thus open new possibilities for contactless friction control, magnetic sensing, and the design of reconfigurable, wear-free frictional interfaces and metamaterials.

Understanding how low-dimensional ferroelectrics respond to ultrafast excitation at nanoscales is essential for controlling energy flow and mechanical functionality in next-generation polar devices, yet the nanoscopic structural response to ultrafast depolarization remains unresolved, obscuring the microscopic pathways of acoustic decoherence and energy dissipation. Here, we spatiotemporally resolve lattice motion in the van der Waals ferroelectric NbOI2 using combined ultrafast electron microscopy and diffraction, revealing three acoustic phonons: two transverse shear modes and one longitudinal breathing mode. The transverse mode that shears the layers perpendicular to the in-plane polar axis dominates over that along the polar axis, reflecting anisotropic polarization-strain coupling. Real-space mapping uncovers spatially correlated heterogeneity in mode amplitudes and lifetimes. Regions dominated by a single shear mode exhibit significantly longer acoustic lifetimes than multimode regions, suggesting acoustic phonon-phonon scattering as a major source of decoherence. Our results provide a microscopic understanding of ultrafast depolarization-driven acoustic dynamics and spatially heterogeneous energy dissipation in van der Waals ferroelectrics.

The Zeroth Law of Thermodynamics states that if two systems are in thermal equilibrium with a third one, then they are also in equilibrium with each other. This study explores not only the final state of thermal equilibrium between ideal gases separated by heat-conducting walls, but also the intermediate stages leading up to equilibrium, using classical molecular dynamics simulations. Two- and three-region models with argon atoms are analyzed. Fluctuations, correlations, and temperature distributions are observed, highlighting how heat conduction between regions influences the time to reach equilibrium. This work is distinguished by its detailed analysis of the intermediate stages that occur until the system reaches thermal equilibrium, in accordance with the Zeroth Law of Thermodynamics.

Materials defects in Josephson junctions (JJs), often referred to as two-level systems (TLS), couple to superconducting qubits and are a critical bottleneck for scalable quantum processors. Despite their importance, understanding the microscopic sources of TLS and how to mitigate them has remained a major challenge. Here, we demonstrate a high-throughput, correlated approach to trace the microstructural origins of strongly-coupled TLS in Josephson circuits. We assembled a massive dataset of TLS across 6,000 Al/AlOx/Al JJs and more than 600 atomic resolution transmission electron microscopy images. We statistically link fabrication, microstructure, and TLS occurrence, revealing a strong correlation between Al electrode thickness, Al grain size, and TLS density. Correspondingly, we find a two-thirds reduction in TLS prompted by a change in electrode fabrication parameters. These results demonstrate a robust, data-driven methodology to understand and control defects in quantum circuits and pave the way for significantly reducing TLS density.

The morphologies of phase separating systems have formal distinctions such as symmetry groups, but the analysis protocol for labeling a particular phase field with a morphology requires manual expertise, arbitrary thresholds, or established signatures. In this work, it is investigated if the angular power spectrum of the 3D structure factor can discriminate between morphologies. The 3D structure factor is computed on configurations of phase separating block copolymers generated by coarse-grained molecular dynamics simulations. The shell of structure factor values containing the primary peaks is isolated. This 2D field on a sphere is decomposed into spherical harmonic modes of even polynomial degree $\ell\le 12$, then further reduced to the rotationally invariant angular power spectrum. It is found that these few coefficients for low $\ell$ discriminate robustly between different morphologies. This analysis serves as an automatic tool for flagging novel structures, without a need to enumerate the plausible morphologies in advance.

The mechanical characteristics of fibers (of various materials), as well as of fiber bundles, are of primary importance for the design and the mechanical behavior of textiles, or of fibrous and composite materials. These characteristics are classically determined from strain-rate controlled tensile testing, generally assuming a negligible role of thermal activation on damage and fracturing processes. Under this assumption, the distribution of individual fiber strengths can be deduced from a downscaling of the macroscopic mechanical behavior at the bundle scale. There are however many experimental evidences of strain-rate and temperature effects on the mechanical behavior of individual fibers or bundles, which can also creep under constant applied load. This indicates a strong role of thermal activation on these processes. Here, these effects are analyzed from a fiber-bundle model with equal-load-sharing, in which thermal activation of fiber breakings is introduced from a kinetic Monte-Carlo algorithm adapted for time-varying stresses. This allows to rationalize these rate or temperature effects, such as a decrease of bundle strength, strain at peak stress, and apparent Young's modulus with decreasing strain-rate and/or increasing temperature. This also shows that the classical downscaling procedure used to estimate the distribution of individual fiber strengths from the mechanical behavior at the bundle scale should be considered with caution. If mechanical testing of the bundle is performed under conditions favoring the role of thermal activation (e.g. low applied strain-rate), this procedure can strongly underestimate the intrinsic (athermal) Weibull's parameters of the fiber strengths distribution. The same model is used as well to explore size (number of fibers) effects on bundle mechanical response.

In 1928, Chapman generalised Einstein's theory of diffusion for non-uniform fluids to show the presence of a non-Fickian diffusion current, which he considered important in thermodiffusion (Ludwig-Soret effect). In 1941, Kiyosi Itô proposed the formal methods of stochastic calculus in the presence of spatially dependent diffusion, yielding the same non-Fickian diffusion current as shown by Chapman. The phenomenon of thermodiffusion and thermophoresis happens in the presence of a temperature gradient, which makes diffusion space-dependent. The role of solvation forces in thermophoresis will only be clearer once that of diffusion is understood properly. In this paper, we investigate the importance of Chapman's non-Fickian diffusion current on the thermophoretic motion of colloidal particles in water (with weak salt concentration). We show that all the general features of variations of the Soret coefficient $S_T$ with temperature can be captured using Chapman's non-Fickian diffusion current. We compare our theoretical results with experimental plots of the Soret coefficients for three polypeptides in aqueous solution: Lysozyme, BLGA, and Poly-L-Lysine, and find a strong match. We emphasise that, in addition to the yet-to-be-understood details of solvation forces, Chapman's non-Fickian diffusion current is an indispensable element that needs to be taken into account for a complete understanding of thermophoresis and thermodiffusion.

Strongly interacting quantum many-body systems are expected to thermalize, however, some evade thermalization due to symmetries. Quantum synchronization provides one such example of ergodicity breaking, but previous studies have focused on open systems. Here, motivated by the problem of ergodicity breaking in closed systems and the study of non-trivial dynamics, we investigate synchronization in a closed disordered Heisenberg spin chain. In the presence of large random disorder, strongly breaking the permutation symmetry of the system, we observe the emergence of spatial synchronization, where spins lock into locally synchronized patches. This behavior can be interpreted as a fragmentation of the global dynamical symmetry $S^+$ into a collection of local dynamical symmetries, each characterized by a distinct frequency. In the weak-disorder regime, still without permutation symmetry, we show that the synchronization mechanism can be understood perturbatively within Krylov space. In the absence of disorder, the Krylov space associated with the dynamical symmetry $S^+$ is two-dimensional. Introducing disorder couples this subspace to the remainder of the Krylov space. This coupling leads only to a second-order correction to the frequency of the dynamical symmetry, thereby preserving coherent oscillations despite the presence of small disorder. At stronger disorder, the perturbation modifies $S^+$ so that it acquires a finite lifetime, providing an example of a transient dynamical symmetry.

Silver interlayers have been shown to enable smooth lithium deposition and cycling in anode-free solid-state batteries. Here, we report the atomic structure of the Ag and Li interface, showing that Li preferentially plates as FCC on both the (111) and (100) Ag surfaces. This forms an energetically favorable coherent interface with Ag, while the BCC phase forms a semi-coherent interface due to large lattice mismatch. We also calculate vacancy formation energies and migration energies for Li diffusion through the interface. We show that vacancy formation energies increase at the interface, leading to an energetic driving force for vacancies to diffuse away from the interface. Additionally, the migration barriers for vacancies from the Ag to the Li are small (29 meV), and therefore promote rapid alloying between Ag and Li. Rapid Li diffusion kinetics directly at the interface leads to smooth deposition of Li, reducing the onset of dendrites. However, diffusion in the 2nd and 3rd Li layers is slower compared to bulk FCC or BCC Li, leading to kinetically hindered alloying when multiple layers of pure Li form. The diffusion kinetics for Ag nanoparticles may be improved by alloying with Mg to expand the Ag lattice constant while forming a solid solution with both Ag and Li.

Despite three decades of experimental study, optical gain in colloidal quantum dots still lacks a microscopic theory capable of explaining gain thresholds approaching one exciton per dot, their size dependence, or the anomalously small effective stimulated-emission cross sections observed across materials. Existing descriptions treat quantum dots as effective two-level systems comprised of an exciton and a biexciton, attributing gain thresholds to biexciton Auger recombination. This assumption is inconsistent with state-resolved optical pumping experiments and basic spectroscopic constraints. Here we present a microscopic theory of optical gain explicitly anchored in the Einstein relations governing absorption and stimulated emission. Within this framework, gain is determined by a spectral balance between stimulated emission from single excitons and excited-state absorption into biexcitonic manifolds, rather than by biexciton lifetimes. Using a spin-boson description of excitons coupled to a lattice bath, we show that gain thresholds and effective gain cross sections are controlled by the interplay of biexciton stabilization and exciton-lattice dressing. The theory unifies disparate materials by quantitatively explaining all longstanding gain phenomenology in CdSe quantum dots and predicts a continuous crossover to effective four-level, near-thresholdless gain in dynamically disordered lattices such as perovskite quantum dots.

Integrated photonics provides a powerful approach for developing compact, stable and scalable architectures for the generation, manipulation and detection of quantum states of light. To this end, several material platforms are being developed in parallel, each providing its specific assets, and hybridization techniques to combine their strengths are now possible. This review focuses on AlGaAs, a III-V semiconductor platform combining a mature fabrication technology, direct band-gap compliant with electrical injection, low-loss operation, large electro-optic effect, and compatibility with superconducting detectors for on-chip detection. We detail recent implementations of room-temperature sources of quantum light based on the high second- and third-order optical nonlinearities of the material, as well as photonic circuits embedding various functionalities ranging from polarizing beamsplitters to Mach-Zehnder interferometers, modulators and tunable filters. We then present several realizations of quantum state engineering enabled by these recent advances and discuss open perspectives and remaining challenges in the field of integrated quantum photonics with AlGaAs.

This work presents a two-stage physics-informed, data-driven constitutive modeling framework for hyperelastic soft materials undergoing progressive damage and failure. The framework is grounded in the concept of hyperelasticity with energy limiters and employs Gaussian Process Regression (GPR) to separately learn the intact (undamaged) elastic response and damage evolution directly from data. In Stage I, GPR models learn the intact hyperelastic response through volumetric and isochoric response functions (or only the isochoric response under incompressibility), ensuring energetic consistency of the intact response and satisfaction of fundamental principles such as material frame indifference and balance of angular momentum. In Stage II, damage is modeled via a separate GPR model that learns the mapping between the intact strain energy density predicted by Stage I models and a stress-reduction factor governing damage and failure, with monotonicity, non-negativity, and complete-failure constraints enforced through penalty-based optimization to ensure thermodynamic admissibility. Validation on synthetic datasets, including benchmarking against analytical constitutive models and competing data-driven approaches, demonstrates high in-distribution accuracy under uniaxial tension and robust generalization from limited training data to compression and shear modes not used during training. Application to experimental brain tissue data demonstrates the practical applicability of the framework and enables inference of damage evolution and critical failure energy. Overall, the proposed framework combines the physical consistency, interpretability, and generalizability of analytical models with the flexibility, predictive accuracy, and automation of machine learning, offering a powerful approach for modeling failure in soft materials under limited experimental data.

Three-dimensional electron gases in strong magnetic fields host partially flat bands that disperse along the field direction yet exhibit Landau-level quantization in the transverse dimensions. Early work established that for spin-polarized electrons confined to the lowest Landau level band, repulsion triggers a charge density wave (CDW) in which electrons 'self-layer' into integer quantum Hall states, while attraction generates a non-Fermi liquid (rather than a superconductor). We revisit this problem with physically motivated deformations – including generalized local interactions, higher Landau level bands, restoration of spin, and explicit breaking of spatial symmetries – paying particular attention to the competition between CDWs and superconductivity. Our main findings are: (1) Generic local interactions can stabilize a nematic CDW in which integer quantum Hall layers spontaneously 'tilt', yielding unconventional Hall response. (2) We numerically establish that the non-Fermi liquid appears stable to perturbations that preserve effective dipole conservation symmetries that emerge within a Landau level band. (3) Upon explicitly breaking translation symmetry, attraction catalyzes a novel layered superconductor that hosts Weyl nodes, superconducts within each layer, and insulates transverse to the layers. These results expand the rich phenomenology of interacting bulk electrons in the high-field regime and potentially inform the design of field-resistant superconductivity in low-carrier-density materials.

Smartphones, laptops, and data centers are CMOS-based technologies that ushered our world into the information age of the 21st century. Despite their advantages for scalable computing, their implementations come with surprisingly large energetic costs. This challenge has revitalized scientific and engineering interest in energy-efficient information-processing designs. One current paradigm – dynamical computing – controls the location and shape of minima in potential energy landscapes that are connected to a thermal environment. The landscape supports distinguishable metastable energy minima that serve as a system's mesoscopic memory states. Information is represented by microstate distributions. Dynamically manipulating the memory states then corresponds to information processing. This framing provides a natural description of the associated thermodynamic transformations and required resources. Appealing to bifurcation theory, a computational protocol in the metastable regime can be analyzed by tracking the evolution of fixed points in the state space. We illustrate the paradigm's capabilities by performing 1-bit and 2-bit computations with double-well and quadruple-well potentials, respectively. These illustrate how dynamical computing can serve as a basis for designing universal logic gates and investigating their out-of-equilibrium thermodynamic performance.

We investigate the properties of trions in transition metal dichalcogenides (TMDCs) monolayers using the Gaussian Expansion Method (GEM) adapted to two-dimensional systems. Excitons and trions in monolayer TMDCs with the chemical composition MX$_2$ in the 2H phase are studied systematically. We computed the associated exciton and trion binding energies. We find in addition to the known $J = 0$ trion the existence of a bound state with orbital angular momentum $J = 1$. The results for $J = 0$ are benchmarked against existing calculations from the Stochastic Variational Method (SVM) and Quantum Monte Carlo (QMC). Furthermore, we analyze the trion internal structure and geometry through their probability density distributions, accounting for the effects of different material shows that GEM – widely used in studies of strongly interacting few-body systems – is well adapted to allow comprehensive and computationally efficient investigations of trions and potentially other weakly bound few-body states in layered materials. In addition, we systematically exploit the effect of strain and dieletric environment in the $J = 1$ trion predictions, illustrated for the MoS$_2$ monolayer example.

Photoluminescence blinking typically degrades the single-photon purity of quantum dot emission. Here, we show that individual CsPbBr$_3$ perovskite quantum dots (PQDs) can exhibit the opposite behavior: low-emitting off states are dimmer and shorter-lived, yet more strongly antibunched than high-intensity on states. Using time-correlated single-photon counting combined with state-resolved second-order correlation analysis, we identify a subset of PQDs in which the zero-delay second-order correlation, $g^{(2)}_0$, decreases upon switching from the on state to the off state, indicating improved single-photon purity. In the most pronounced case, $g^{(2)}_0$ decreases from 0.23 in the on state to 0.08 in the off state. We attribute this counterintuitive behavior to self-trapped-exciton-mediated suppression of the biexciton–exciton cascade, which suppresses multiphoton emission more effectively than single-exciton emission. These findings reveal an unconventional blinking regime in PQDs and show that blinking does not necessarily degrade single-photon purity.