Papers

We introduce a utility-driven bounded-confidence model of opinion dynamics in which opinions associated with higher utility exert stronger social influence. In the regime where all agents belong to a single opinion cluster, we derive a stochastic differential equation for the mean opinion and show that its stationary distribution is Gibbs-like, with an effective potential determined by the utility landscape and an inverse temperature controlled by the learning rate and the number of agents. For multimodal utility functions, the dynamics exhibit metastability and spontaneous switching between competing opinion states. The reduced stochastic description also captures the evolution and merging of multiple opinion clusters, in agreement with agent-based simulations.

The ternary transition-metal oxide Fe$_2$Mo$_3$O$_8$ is a polar magnet characterized by a layered structure of magnetic Fe honeycomb lattices and non-magnetic Mo kagome lattices. Whereas previous studies have primarily focused on the chemical substitution at the Fe sites to modulate the magnetic properties, the Mo sites have remained largely unexplored due to the strong spin-singlet trimerization of Mo$^{4+}$ ions. In this study, we investigated the effect of substituting non-magnetic Pb$^{4+}$ and Zr$^{4+}$ ions into the Mo sites to intentionally disrupt the Mo trimers. Our results reveal that the disruption of the Mo spin-singlet state induces active spins within the Mo layer, resulting in the emergence of a ferromagnetic-like behavior that persists even at room temperature. Quantitative analysis that takes into account the weight fraction of the main phase suggests an effective spin $S = 1/2$ state per active Mo ion upon trimer disruption. These findings demonstrate that controlling non-magnetic cluster states within a polar host via chemical substitution is a promising approach for designing room-temperature magnetoelectric materials.

This study investigates the effect of long-term UV radiation exposure on the mechanical and structural properties of selected polymeric materials - PLA, ABS, ABST, PETG, HIPS and PC - fabricated using 3D-print based Fused Filament Fabrication (FFF) method. Existing research in the field of polymers weathering has predominantly examined combined degradation factors (UV irradiation, humidity and thermal cycling) over the timescales rarely exceeding a few months, which prevents attribution of property changes to individual agents. To isolate the contribution of UV radiation specifically, samples were exposed up to 7744 consecutive hours (i.e. 322 days) of UV irradiation in an environmental cell with controlled humidity and temperature. The mechanical properties were characterized using nanoindentation, which allows for spatially resolved measurements of hardness and elastic modulus in the near-surface region, thereby enabling the detection of degradation gradients on the order of tens of micrometers. The lack of methodological consistency in the current literature hinders the cross-material comparison; this study addresses the gap by applying nanoindentation uniformly across wide range of selected materials prepared and tested under identical conditions, while studying these properties after a very long exposure to UV radiation.

Phonon polaritons have attracted increasing interest as a means to offset the reduction in phonon thermal conductivity in nanostructures caused by enhanced boundary scattering. However, the interpretation of the limited experimental data on phonon polariton-mediated conduction is hindered by the lack of comprehensive full-wave models for predicting thermal electromagnetic transport in solid-state systems. Here, the radiative thermal conductivity in the diffusive regime along SiO2 nanowires near room temperature is predicted using the fluctuational electrodynamics-based discrete system Green's function method. At 400 K, for nanowire diameters of 66 nm and 132 nm, modest radiative conductivities of 0.0264 W/m-K and 0.0165 W/m-K, respectively, are obtained, with contributions dominated by surface phonon polaritons. In contrast, the kinetic theory combined with nanowire dispersion relations derived from Maxwell's equations predicts conductivities that can be nearly two orders of magnitude larger than those obtained from fluctuational electrodynamics, and are largely dominated by bulk phonon polaritons propagating within the nanowire volume. Improved agreement between the kinetic theory and fluctuational electrodynamics for the total radiative conductivity can be achieved by introducing an effective mean free path that accounts for the reduced mean free path of bulk phonon polaritons outside the Reststrahlen spectral bands of SiO2. However, even with this correction, the kinetic theory fails to accurately capture the spectral distribution of radiative conductivity. This work establishes a solid foundation for the development of phonon polariton-based systems for thermal management in micro/nanoelectronic devices.

We show that, contrary to common belief, supersymmetry alone is not sufficient in Model A dynamics to ensure relaxation toward a stationary state satisfying time-reversal invariance (TRI). An additional condition on top of supersymmetry is required for TRI, which we analyze in detail. We explicitly construct a model that is supersymmetric but violates TRI, and argue that, at least perturbatively, TRI nevertheless emerges as an effective large-scale symmetry. Using the functional renormalization group (FRG), we further show that the dynamical effective action, $\Gamma[\varphi,\tilde\varphi]$, contains the derivative of the equilibrium effective action, $\Gamma^{\mathrm{eq}}[\varphi]$, whose renormalization-group flow is identical to that of the equilibrium theory order by order in the derivative expansion. Finally, extending the same line of reasoning, we show that the probability distribution of the total magnetization in the Ising model can be recovered within the Model A framework.

We investigate with first principles theoretical methods optical response accounting for excitonic effects of quasi-one dimensional monolithic arrays of graphene nanostripes – two-dimensional graphene superlattices, where quasi-metallic and dielectric regions alternate by selective hydrogenation of graphene. It is shown that chemical engineering of the graphene surface can lead to strong and well-isolated absorption peaks in the far-infrared and possibly even terahertz frequencies. The band gap scaling suggests no excitonic insulators.

The effects of compocasting process parameters on some structural and tensile characteristics of the A356-10% SiCp (volume fraction) composites were studied. Semisolid stirring was carried out at temperatures of 590, 600 and 610 C with stirring speeds of 200, 400 and 600 r/min for 10, 20 and 30 min. The distribution of the SiC particles within the matrix, porosity content and tensile properties of the obtained samples were examined. The structural evaluations show that by increasing the stirring time and decreasing the stirring temperature, the uniformity in the particle distribution is improved; however, by increasing the stirring speed the homogeneity firstly increases and then declines. It is also found that by increasing all of the processing parameters, the porosity content is enhanced. From the tensile characteristics viewpoint, the optimum values of the speed, temperature and time are found to be 400 r/min, 590 C and 30 min, respectively. The contribution of the reinforcement distribution uniformity prevails over that of the porosity level to the tensile properties.

A recent Letter by Wadhia et al. reports a realization of a quantum clock using a double quantum dot (DQD) [Phys. Rev. Lett. 135, 200407 (2005)]. This Comment identifies two fundamental issues: (I) the claimed “quantum clock" exhibits only classical behavior and lacks intrinsic temporal correlations between ticks; it is not sufficient for accurate time as a good clock. (II) the thermodynamic analysis misassigns entropy production and conflates amplification with measurement; the reported combined entropy is an engineering dissipation, not a fundamental cost of quantum timekeeping.

We develop a long-wavelength theory for the linear stability of a flat interface between an active nematic and an isotropic fluid. Starting from a diffuse-interface Cahn–Hilliard–Landau–de Gennes description coupled to Brinkman-screened Stokes hydrodynamics, we project the linearized dynamics onto a small set of interfacial degrees of freedom: the conserved translation, or height, mode; a scalar profile distortion or amplitude mode; and a transverse orientational mode associated with director rotations. Eliminating the gapped scalar profile mode gives a reduced interfacial operator coupling the conserved height mode to the transverse orientational mode. The main result is that activity generates, in the screened diffuse-interface regime, a direct local contribution proportional to $q^2$ in the height sector. This term competes with the passive local diffusive capillary relaxation, which enters at order $q^4$, and defines a local active interfacial channel controlled by the internal structure of the diffuse interface. This mechanism is distinct from the non-analytic $|q|$ and $|q|q^2$ terms characteristic of weakly screened Hele–Shaw/Saffman–Taylor-type transport, which are controlled by long-ranged momentum transport in the surrounding fluid. This framework identifies a diffuse-interface route to active interfacial instability that can operate while the homogeneous active nematic remains linearly stable because of hydrodynamic screening. It also provides a basis for distinguishing local diffuse-interface instabilities, bulk-flow-driven hydrodynamic instabilities, and mixed regimes in active nematic–isotropic interfaces.

Self-driving laboratories or autonomous experimentation are emerging as transformative platforms for accelerating scientific discovery. Bayesian optimization (BO) is among the most widely used machine learning frameworks for these purposes, but these BO-based frameworks rely on predefined scalar descriptors to guide experimentation. In many situations, the determination of an appropriate scalar descriptor can be challenging, and may fail to capture subtle yet scientifically important phenomena apparent to experts with interdisciplinary insight. To overcome this limitation, here we develop deep-kernel pairwise learning (DKPL), an approach for autonomous microscopy experiments which incorporates human expertise and interdisciplinary scientific knowledge into an active learning loop. Instead of relying on explicit scalar objectives, DKPL enables experts to directly evaluate which experimental output is more promising using interdisciplinary knowledge. DKPL then learns a latent utility function from these expert judgements to guide subsequent autonomous microscopy experiments. We demonstrate DKPL's performance in learning physically meaningful nanoscale structures while effectively prioritizing high-information measurement regions using an experimental model dataset with known ground truth. We further apply DKPL to analyze the character of ferroelectric domain walls, where we find DKPL capable of distinguishing between high and low characteristic domain-wall angles in bismuth ferrite, and able to discover both head-to-head and tail-to-tail domain-wall character in erbium manganite. This development establishes an approach to integrate expert knowledge into autonomous microscopy experiments and demonstrates a pathway toward expert-guided self-driving laboratories capable of addressing scientific problems beyond the limits of scalar-metrics-driven learning.

We investigate the emergence of synchronization in a network of coupled chaotic macroeconomic systems. Each node represents an economy characterized by three key variables savings, gross domestic product (GDP), and foreign capital inflows. These economies interact or are connected through a fitness-based probability that depends on the potential GDP of each node. This formulation allows both structural heterogeneity, arising from uneven network connectivity, and dynamical heterogeneity, due to differences in local parameters, to be explored within a unified framework. Using both numerical simulations and a mean-field approximation, by varying the coupling strength and the degree of heterogeneity of both network topology and dynamical behavior of the nodes, we analyze synchronization transitions. Our results show that the mean-field approach accurately captures the collective dynamics in homogeneous and fully connected networks even with heterogeneity within the intrinsic dynamic of the nodes but fails when strong heterogeneity in the structure of the network is introduced. In heterogeneous networks, the system exhibits partial synchronization and on–off intermittency, where coherent phases of global synchronization alternate with abrupt desynchronization bursts. The distribution of laminar phase durations follows a power-law scaling, consistent with theoretical predictions for intermittent synchronization. From an economic perspective, these results suggest that global business cycle synchronization is inherently fragile: strong integration can promote temporary coordination among economies, but structural and dynamical disparities inevitably lead to intermittent breakdowns of collective behavior.

Serpentinization of ultramafic rocks is a naturally occurring mineralogical process that can generate molecular hydrogen through the oxidation of ferrous iron during water-rock reaction. Although the resource potential is large, the natural reaction is kinetically limited, and practical hydrogen recovery requires methods that can accelerate conversion without imposing an energy penalty that exceeds the value of the hydrogen produced. This short communication reports a preliminary atmospheric-pressure microwave serpentinization experiment using a water-saturated 2 g crushed olivine sample. Microwave irradiation produced a rapid increase in measured hydrogen concentration compared with conventional hot-plate heating under otherwise similar conditions. The preliminary experiment showed approximately a 12-fold increase in hydrogen concentration and an apparent rate increase from about 2 ppb s$^{-1}$ for conventional heating to about 10 ppb s$^{-1}$ during microwave exposure. These results suggest that electromagnetic stimulation can enhance serpentinization kinetics, likely through rapid volumetric heating, selective coupling to iron-bearing phases, and localized thermal gradients. The result provides an initial experimental basis for evaluating microwave stimulation as a route to accelerated geologic hydrogen production and motivates follow-on measurements using calibrated gas analysis, absorbed-power measurements, dielectric characterization, and elevated-pressure testing.

We obtain an exact expression for the conductivity of a disordered, non-Galilean-invariant Fermi liquid by solving the kinetic equation with both screened Coulomb and $z=3$ Pomeranchuk critical interactions. While consistent with previous asymptotic results, our solution shows that electron-electron interactions enter the conductivity solely via the quasiparticle scattering time, $\tau_\mathrm{ee}$. Accordingly, the crossovers between the collisionless and hydrodynamic regimes occur when $1/\tau_\mathrm{ee}$ becomes comparable to the larger of the impurity scattering rate and the probe frequency, $\Omega$. In addition, the exact solution yields the optical response in the hydrodynamic regime, $\Omega\ll 1/\tau_\mathrm{ee}$, which is inaccessible within perturbation theory. Near a $z=3$ Pomeranchuk quantum critical point, consistency between the kinetic-equation and Kubo approaches requires proper inclusion of mass renormalization within the Eliashberg approximation, which also ensures that the crossover between the collisionless and hydrodynamic regimes in the optical conductivity occurs at the Planckian scale $\Omega\sim T$.

We predict an antipolar instability in hexagonal LaN using first-principles density functional theory. Starting from a nonpolar hexagonal phase, we identify competing polar and antipolar zone-center phonon instabilities. Condensation of the polar and antipolar modes stabilizes, respectively, dynamically stable wurtzite (WZ) phase and an hexagonal antipolar (AP) phase which is characterized by alternating local polarization and zero net macroscopic polarization within the unit cell. At ambient conditions, the AP phase is metastable with respect to the WZ phase, and a finite energy barrier exists between these phases, suggesting a possible polarization-switching pathway via the AP intermediate state. The energy barrier between the WZ and AP phases decreases with increasing pressure, indicating enhanced tunability between polar and antipolar states. The sublattice polarization increases with pressure in the AP phase, while it decreases in the WZ phase. We further find that, with increasing pressure, the rock-salt and tetragonal phases of LaN become more stable than the hexagonal phases (AP and WZ). Consequently, the realization of the AP phase is more favorable in the low-pressure regime, where hexagonal phases remain energetically competitive. These results demonstrate pressure-driven competition between polar and antipolar phases in LaN and point toward antiferroelectric-like behavior in this binary nitride system.

Defects are both physically rich objects and powerful tools in modern quantum field theory. They are extended operators, such as boundaries, impurities, and probe particles, embedded in many-body systems. In this dissertation, we study the universal aspects of defect dynamics from the perspective of symmetry principles. We bring together several themes, including defect renormalization group flows, effective string theory, and impurities in atomic quantum gases.

Generating usable output-entanglement in continuous variable systems can serve as a viable resource for improving applications in quantum information science. In this work, we show how to generate steady-state output-entanglement in a two-stage conversion setup between optical and microwave photon which employs resonantly coupled magnetic and mechanical excitations, as proposed in Phys. Rev. Applied 18, 044059 (2022). We show that the entanglement can be maximized for the same set of parameters which optimize the frequency-conversion efficiency, and that it can be leveraged for a teleportation-based state-transfer protocol for coherent input-states with fidelity close to unity. We propose an implementation based on an Yittrium Iron Garnet disk of micrometer scale, and use both simulation results and reasonable estimates to assess the performance under optimized conditions. We find a maximum teleportation fidelity of $0.75$ for the proposed setup.

DNA origami is a powerful method to achieve nanoscale folded structures. Despite rapid improvements in folding and purification methods, DNA origami objects are still often produced in small quantities and studied at single molecule scale. Here, we design simple DNA origami-inspired polymers with complex topologies, and study their rheology and viscoelastic properties in dense conditions. First, we designed and purified topologically distinct DNA nanostructures, linear, circular, and "tadpole" polymers, to evaluate how polymer architecture influences entanglement and rheology. Despite their distinct topologies, we observe that all constructs obeyed universal rheological scalings, likely due to their short length. However, upon thermal annealing in the bulk, the DNA origami-like polymers displayed significantly different behaviours. Our results suggest that DNA origami-like polymers could be used to engineer thermoresponsive behaviours in complex fluids by introducing reversible and topology-dependent crosslinking.

Sampling from discrete distributions with multiple modes and energy barriers is fundamental to machine learning and computational physics. Recent discrete neural samplers like MDNS suffer from mode collapse and fail to sample high-energy barrier regions between modes, which is critical for free energy estimation and understanding phase transitions. We propose Metadynamics Discrete Neural Sampler (MetaDNS), a general framework integrating well-tempered metadynamics into discrete diffusion or autoregressive samplers. By maintaining an adaptive, history-dependent bias potential along selected low-dimensional coordinates, MetaDNS forces exploration of previously inaccessible regions, enabling free energy reconstruction infeasible with standard neural samplers due to a lack of high-energy samples. On challenging low-temperature benchmarks including Ising, Potts, and the copper-gold binary alloy, MetaDNS reproduces the thermodynamic distribution. Compared to MCMC-based metadynamics, MetaDNS also achieves comparable exploration requiring fewer bias deposition steps.

We present a review on quantum metrology and sensing, from its foundations to current applications. Highlights of the review include consideration of both frequentist and Bayesian approaches to parameter estimation; single as well as multiparameter estimation; estimation for different encoding processes comprising unitary as well as noisy channels, quantum thermometry, and channels involving indefinite causal order; different estimation strategies incorporating also recent advances like quantum error correction-aided methods and reservoir engineering; usefulness of quantum Fisher information to detect resources; applications of quantum metrology in diverse arenas covering quantum many-body sensors, sensing protocols in atomic ensembles, atom-photon systems, and continuous-variable systems, quantum imaging, quantum illumination, atomic clocks and atom interferometry, etc; and experimental realizations of quantum sensors in different physical platforms.

Superconducting two-dimensional materials, and in particular few-layer graphene, offer an exciting platform for low-power electronics, yet the origin of their unconventional superconductivity remains an open question. Prevailing theories, primarily rooted in the Bardeen-Cooper-Schrieffer (BCS) framework that assumes electron-phonon interactions are the main mechanism of superconductivity, struggle to account quantitatively for the observed phenomena. Recent studies point to a plasmonic pairing mechanism in graphene systems; however, disentangling the relative contributions of phonon- and plasmon-mediated pairing remains challenging due to the lack of a satisfactory first-principles framework capable of accurately capturing dynamical screening effects in the electronic channel. Here, we present a new theoretical framework that extends the quasiparticle self-consistent GW method to the superconducting phase by coupling it with the Eliashberg treatment of both phonon- and plasmon-mediated interactions. Our approach, termed superconducting quasiparticle GW (s-qpGW), is on par with the state-of-the-art Eliashberg theory of superconductivity when applied to bulk metals, and correctly predicts the absence of superconductivity in doped monolayer graphene. To differentiate s-qpGW from conventional Eliashberg approaches, we study a simple model system, graphene with an artificially enhanced density of states, and demonstrate that s-qpGW captures dynamical Coulomb screening effects in ways that standard BCS theory cannot.

This research paper investigates new and first insights into the magnetic and magnetocaloric properties of one-dimensional (1D) cobalt ferrite CoFe2O4 (CFO) nanofibers elaborated by sol gel based electrospinning technique, particularly focusing on their behavior at low temperatures for specific applications. The calcined CFO nanofibers microstructural, structural, magnetic, and magnetocaloric properties were explored. The nanofibers (NFs) microstructure, with an average diameter of 210 nm, was examined by scanning and transmission electron microscopies (SEM, TEM). The X-ray diffraction (XRD) of the CFO nanofibers showed a pure cubic close-packed (c.c.p) spinel crystalline structure with the F d 3 -m space group. The Raman spectroscopic studies further confirm the cubic inverse spinel phase. The Magnetic properties were explored as a function of temperature, ranging from 10 to 300 K, a ferromagnetic behaviour was observed with the highest saturation magnetization of 75.87 emu g(-1) and a coercivity of 723 Oe at room temperature. The variation of the magnetic entropy was measured indirectly using the Maxwell approach with an increasing magnetic field. A maximum of Delta(S)=1.71 J K-1 was reached around 32 K. At 180 K, the associated adiabatic temperature change, Delta (Tmax), was 0.93 K, with a large RCP value of 7.58 J kg-1 was measured, which is reasonably high for the corresponding nanoparticles (NPs). This work may suggest that 1D CFO nanofibers offer a promising route for the production of nanostructured magnetic materials, potentially impacting various electronic and electromagnetic device applications at low temperatures.

Lead-free halide double perovskites are promising alternatives to Pb-based semiconductors, but their discovery is challenging because structural formability, thermodynamic stability, band-gap placement, optical-transition strength, dielectric screening, and carrier transport must all be satisfied within the vast A2BB'X6 space. We present a backward-mapping, genome-guided framework linking device-level targets to chemically interpretable descriptor families for Pb-free double-perovskite discovery. From 13,088 charge-balanced compositions, we apply a halide-aware workflow integrating geometric formability filtering, six-family chemical-genome descriptor encoding, evolutionary-optimized machine learning surrogates, SHAP-based interpretation, and DFT phenotype closure. Stability is modeled using Ehull-derived labels, while a band-gap surrogate predicts scalar-relativistic PBE Eg for target-driven selection. The funnel reduces the search space to seven DFT-validated candidates: K2BePdF6, K2MnCdCl6, Rb2TeCuBr6, Cs2SnGeBr6, Cs2GeSrBr6, Cs2NiBaI6, and Cs2AgInCl6, all verified for structural assignability, band-edge character, effective masses, dielectric response, optical absorption, conductivity, reflectivity, energy-loss spectra, and XRD fingerprints. Functional rules emerge from stability-function coupling rather than band-gap optimization alone, providing an interpretable inverse-design paradigm to accelerate Pb-free double-perovskite discovery.

We ask whether the standard treatment of dropout as a static hyperparameter is optimal, or whether its utility can be improved by letting it vary over depth. We answer this by developing a mean-field theory of dropout near the edge of chaos, identifying distinct universality classes for smooth and kinked activations, together with their scaling exponents. The resulting propagation theory, constrained by maximizing the regularization delivered by dropout, motivates concentrating dropout near the input. Experiments on vision, speech and financial time series show gains most consistently in MLPs, with smaller gains in Transformers.

We develop a direct diagrammatic Monte Carlo method for the second Rényi entropy of inter- acting lattice fermions. Fermionic replica sewing yields a connected-determinant (CDet) expansion, which we sample with many-configuration Markov-chain Monte Carlo. On a 3 \times 3 Hubbard clus- ter, deterministic coefficients through third order agree with exact-diagonalization derivatives for three reference shifts, while sampling extends the series to tenth order. For a reference shift with a continuous stability region, conformal-Borel resummation also gives good agreement with the exact entropy. We further compute coefficients through ninth order on 40 \times 40 and 50 \times 50 periodic lat- tices, with subsystems of up to 676 sites. The resummed results from different reference shifts show good agreement at a common truncation order. Their shift and order dependence provide checks on the stability of the continuation. These calculations extend connected-diagram sampling to spatial Rényi observables on large finite fermionic systems.

Tunneling spectroscopy and its evolution are crucial for elucidating the intricate electronic structure and emergent phenomena in quantum materials.Nevertheless, high-quality measurements – specifically those tracking evolution across temperature and external fields – remain a formidable challenge. We have fabricated a high-quality $\mathrm{TaO}_x$-based planar tunneling junction by using magnetron sputtering for van der Waals (vdW) superconductors. Using the vdW superconductor $\mathrm{Bi}_2\mathrm{Sr}_2\mathrm{CaCu}_2\mathrm{O}_{8+\delta}$ (Bi2212) as a benchmark, this platform yields high-quality tunneling spectra, reproducing the electronic signatures obtained from scanning tunneling spectra acquired from atomically clean surfaces under ultra-high vacuum conditions. This architecture enables high-precision spectroscopy across extensive temperature and magnetic field ranges, offering a universal strategy for probing the electronic structures of diverse two-dimensional systems and facilitating future explorations of material properties.

Dissipative quantum chaos is an emerging theory that is expected to extend the ideas, concepts, and methodology of conventional Hamiltonian quantum chaos from coherent evolution to open quantum dynamics. The new theory should provide a set of tools to distinguish chaotic open quantum systems from integrable ones, as well as quantitative measures of their chaoticity (or, conversely, integrability). The foundations of this theory were laid in the late 1980s, and from the very start it was clear that, like its Hamiltonian predecessor, it had to be based on the spectral properties of the operators governing open quantum evolution. After these first steps, the field remained relatively quiet for many years and it is only over the last decade that the development of dissipative quantum chaos has received a strong boost, as confirmed by a large number of publications on this topic and, very recently, the first experiments performed to test its theoretical predictions. In this chapter, we review these recent developments and outline the basic foundations of dissipative quantum chaos.

We investigate chiral superconductivity emerging from parent electronic states with non-uniform Berry curvature, motivated by recent experiments in rhombohedral graphene multilayers. Using the continuum $\lambda_N$-model-a tunable platform with independently controllable Berry curvature profiles-we solve the full BCS gap equation on a continuum Chern band beyond the weak-coupling limit. We find that a non-uniform Berry curvature of the parent band enriches the superconducting order parameter, leading to the formation of momentum-space vortices in the gap function away from high-symmetry points. By tuning the Berry curvature profile, we identify distinct regimes associated with vortex nucleation and vortex number saturation, and show that the nucleation of momentum-space vortices tends to lower the condensation energy. We then show analytically that the parent band Chern number constrains the number of momentum-space vortices that can nucleate in the gap-independent of details of the $\lambda_N$-model. We also provide a gauge-invariant formulation for computing the Bogoliubov-de Gennes (BdG) Berry curvature for continuum models, and find that it is determined by a momentum-space phase current. The winding of this current around vortices in the occupied region in turn determines the BdG Chern number. Finally, we discuss how thermal Hall measurements can be used to probe the formation of momentum-space vortices. Our results highlight the crucial role of Berry curvature in shaping chiral superconductivity, and offer guiding principles for its identification in systems such as rhombohedral graphene.

Altermagnetic order, characterized by the Néel vector, breaks time-reversal symmetry (TRS) even in the nonrelativistic limit. Although spin-polarized and anomalous transport phenomena emerge with this order, they are mutually compensated by TRS-connected antiphase domains with opposite Néel vectors. Here we employ polarized neutron diffraction to directly probe the altermagnetic order in MnTe. Pronounced nuclear-magnetic interference terms were observed, providing direct evidence of a net Néel vector in the bulk crystal. Moreover, a weak ferromagnetic moment (WFM), originating from relativistic spin-orbit coupling, was found to be coupled with the altermagnetic order. Both the altermagnetic order and the WFM can be switched by milli-Tesla-scale magnetic field cooling.

High entropy oxides (HEOs) are a class of materials with vast compositional space and tunable properties, making them attractive for applications in thermoelectrics, magnetism, ionic conduction, and beyond. However, their metastable nature makes the local structure, and consequently their properties, highly sensitive to growth conditions. It is therefore essential to probe the local modulations in atomic, chemical, and electronic structure as a function of growth conditions. Here, advanced S/TEM techniques, including 4D-STEM combined with electron energy loss spectroscopy and energy-dispersive X-ray spectroscopy are used to investigate the effect of substrate temperature on structure and strain at the nanoscale regime in HEO thin films. We quantify how nanoscale strain variations correlate with Co valence and subtle chemical differences in the films with the same nominal composition but different growth temperatures. Our results demonstrate that identical HEO compositions can accommodate distinct strain and defect states in thin film form and highlight how synthesis conditions can be leveraged to manipulate strain and Co valence. These findings establish a framework to tailor functional properties via strain and valence control in high entropy oxide thin films.

We introduce a matrix product operator (MPO) encoding of the Magnus expansion and the Dyson series for one-dimensional quantum lattice models with time-dependent Hamiltonians. The MPO construction can be made accurate up to arbitrary order in the time step, it can be applied to both finite and infinite systems, and it can handle long-range interactions. The resulting MPO can be combined with state-of-the-art time evolution algorithms based on matrix product states, allowing for drastic improvements in simulating evolution under time-dependent Hamiltonians. Our MPO construction can also be used for the optimization of quantum circuits in the context of quantum simulation of time-dependent Hamiltonians.