The origin of some mesophases of the ferroelectric nematic realm is not yet well understood. In this work we study the highly polar liquid crystal MIO, a close structural analogue of the prototypical ferroelectric nematogen DIO, which exhibits a ferroelectric smectic A to ferroelectric smectic C (SmAF-SmCF) phase transition. Calorimetric, dielectric and light-scattering experiments reveal that it is a second-order phase transition with mean-field behavior, and is driven by the softening of the tilt elastic constant accompanied by the divergence of the amplitude of the associated dielectric mode.

Characterizing electronic band structures requires precise knowledge of wave functions and their quantum geometry. Here, we introduce a tomography method to reconstruct the density matrix of electron states from quasiparticle interference maps around single impurities. We consider two-orbital models on a honeycomb lattice, relevant to graphene heterostructures and direct-gap semiconductors. For on-site impurities, backscattering between time-reversed states directly maps the density matrix populations and coherences into distinct orbital contributions in the interference map. While local probes usually lack orbital resolution, these orbital contributions transform under distinct symmetry group representations and can thus be disentangled to reveal the density matrix and quantum geometric tensor of the scattering states. This establishes impurities as tomographic probes for band structures in scanning tunneling microscopy using conventional, unpolarized tips.

Hyperuniform systems strongly suppress long-wavelength density fluctuations, which is quantitatively characterized by the small-wavenumber scaling. In finite samples, however, accurately estimating the hyperuniformity exponent α can be challenging. The inferred value depends strongly on the range of length scales accessible in the measurement, finite-size effects, and the specific characterization method employed, whether based on Fourier-space structure factors, real-space density fluctuations, or dynamical probes such as diffusion spreadability. In particular, the structure-factor method provides the most direct estimate of α, but is sensitive to empirical low-k fitting cutoffs. The number-variance method offers a real-space Class-like diagnosis, but contributes a numerical exponent only when the finite-size data retain Class III-like scaling information. The spreadability method provides a smoother dynamic estimate and reduces configuration-level fluctuations, but requires a physically admissible long-time fitting window. Here, we develop a practical method-aware protocol for robust estimation of the effective scaling exponent α in finite-size hyperuniform point configurations, combining three complementary methods with distinct roles. Our protocol summarizes the method-specific estimates through a joint empirical estimator and reports the internal dispersion among the participating methods to determine the optimal estimate.

We propose a physical realization of the unstructured database search that works via classical, dissipative model of spherical spins. The database is implemented via spin-spin couplings, where the selected coupling refers to a larger ferromagnetic interaction between two selected spins. The low-temperature equilibrium of this model leads to magnetization strongly concentrated on the selected spins, which means that the search is complete. The search time refers to the relaxation time to equilibrium from a homogeneous initial state, and is described via Langevin equations. This time scales as ${\cal O}(M^a)$ with $a<1/2$, where $M$ is the database volume. This is faster than Grover's search, showing how a dissipative, classical analog computer can overcome the quantum unitary computer.

Silicon-vacancy (SiV) centers in diamond combine near-infrared emission with solid-state robustness, but their performance hinges on isolating favorable defect charge states. We demonstrate static and dynamic control of ultra-shallow (<15 nm) SiV ensembles in type IIa diamond. By combining low-energy ion implantation with tailored oxygen and hydrogen terminations, we map regimes that maximise the fluorescent SiV- population over dark charge states. We then realize reversible SiV- to SiV0 conversion using aqueous electrolytic gating with sub-200 mV biases and low optical powers. Our results enable low-power electrical control of SiV ensembles for integrated quantum photonics and biologically compatible voltage imaging in the near-infrared.

Out-of-time-order correlators (OTOCs) provide a fundamental metric for quantum chaos, but capturing the fine structure of information scrambling requires exploring their higher-order generalizations. Here, we systematically investigate the sequence of higher-order OTOCs in a Luttinger liquid and its lattice realization, the XXZ Heisenberg chain. Using bosonization and numerics, we extract the full temporal dynamics of the first three OTOCs, revealing that they rapidly erase memory of the initial state, and quickly saturate to their steady state values. Strikingly, we show that calculating the late time saturation values for the entire sequence of higher-order OTOCs maps exactly onto determining the partition function of a non-Hermitian Harper model. Through this mapping, we demonstrate that for moderately strong interactions, the steady-state OTOCs become parametrically small up to the seventh order, mimicking higher $k$-design. Our results reveal that Luttinger liquids exhibit an unexpectedly profound degree of apparent scrambling when viewed through the lens of higher-order OTOCs.

We report an experimental investigation of the magnetic microstructure of iron oxide multicore assemblies by means of polarized small-angle neutron scattering (SANS). Guided by a recently developed analytical theory for vortex-state magnetic nanoparticles, we provide a quantitative comparison between the measured and calculated cross sections, revealing signatures that are consistent with vortex-type magnetization configurations at low applied magnetic fields. In particular, the field evolution and the characteristic isotropic ring-type feature of the spin-flip scattering intensity at intermediate momentum transfers are in line with the formation of flux-closure states. The latter are stabilized by the interplay of exchange, Zeeman, and magnetostatic energies. The methodology allows for a statistically significant characterization of vortex states in densely packed nanoparticle systems, thereby complementing surface-sensitive techniques that are commonly limited to the observation of spin structures in individual particles.

We show that the broad X-ray photoelectron lines of silicon oxide on silicon arise from a continuous statistical distribution of core-level binding energies. Statistical simulations spanning compositions from Si to SiO$_2$ reproduce the full extent of this broadening, reaching 5 eV for SiO$_{1.0}$ , in quantitative agreement with 0.23 nm layer-resolved spectra reconstructed from Ar$^+$ sputtering data. This continuous distribution blurs distinct spectral fingerprints of local structural motifs, thereby challenging conventional chemical state assignment in oxide X-ray photoelectron spectra.

We present a method to compute Ewald summation for the irreducible components of flow around active particles to study hydrodynamic interactions in active colloidal suspensions. An active particle is modeled as a colloidal sphere with a surface slip velocity. Using this model, we obtain an irreducible representation of the fluid flow produced by an active particle in periodic geometry of Stokes flow for an arbitrary surface slip. The solution of the active flow is obtained in terms of lattice sum of the Oseen tensor and their derivatives. The lattice sum is accelerated using the Ewald summation technique. We apply the method to compute explicit expression for rigid body motion of hydrodynamically interacting active particles. Our method presents a way for dynamic simulation of active particles due to arbitrary mode of active slip in periodic geometry of Stokes flow.

Altermagnetism defines a third fundamental class of collinear magnetic order, featuring compensated magnetic moments with antiparallel spin alignment, yet lifted Kramers degeneracy without the need for relativistic spin-orbit coupling. Its ability to host spin-polarized electronic bands and unconventional chiral magnons makes it a promising platform for functional materials. However, experimental verification has proven challenging; while circular dichroism in resonant inelastic X-ray scattering (RIXS) has been suggested as a signature of chiral magnons, it remains controversial whether this effect is an intrinsic property of altermagnetism or an artifact of experimental geometry. In this work, we resolve this debate and provide unambiguous experimental evidence of $d$-wave altermagnetism in the strongly correlated Lieb-lattice magnet La$_2$O$_3$Mn$_2$Se$_2$. The RIXS spectra exhibit a $d$-wave-symmetry circular dichroism in the magnetic excitations that vanishes in the paramagnetic phase. Through RIXS-operator symmetry analysis and exact-diagonalization calculations, we prove that the observed dichroism is a direct consequence of altermagnetic symmetry constraints, independent of magnon branch splitting. Our results provide definitive evidence for the experimental realization of $d$-wave altermagnetism in La$_2$O$_3$Mn$_2$Se$_2$ and establish circularly polarized RIXS as a highly symmetry-sensitive spectroscopic framework for detecting magnetic phases that evade conventional probes.

We study Josephson dynamics in a long atomic Bose-Josephson junction formed by two tunnel-coupled coplanar Bose-Einstein-condensate rings. An in-plane linear acceleration breaks the axial symmetry of the trap and transforms a single Josephson plasma oscillation into a multimode population-imbalance response. Gross-Pitaevskii simulations and Bogoliubov-de Gennes analysis show that the additional spectral components arise from collective modes that acquire finite overlap with the population-imbalance operator under symmetry breaking, with their activation governed by reflection symmetry about the acceleration direction. We also propose a mode-resolved Josephson-spectroscopy protocol based on a weak localized periodic perturbation. Frequency scans reveal resonant amplitude peaks and phase shifts at the eigenfrequencies of active Bogoliubov modes, while angular scans of the drive position provide access to the angular structure of the corresponding mode density perturbations. A dissipative time-dependent Bogoliubov theory yields analytical response functions in quantitative agreement with full Gross-Pitaevskii simulations in the linear regime. Our results demonstrate that accelerated dual-ring condensates provide a controllable platform for symmetry-selected Josephson dynamics and spectroscopic probing of collective modes.

Thermally driven quantum-orders observed in exceptional instances may redefine the role of thermal-fluctuation from a source of decoherence to a resource for coherent-state engineering. While preliminary signs of counterintuitive temperature-rise-triggered superconductivity manifested in CeCu2Si2, ErRh4B4, Ho1.2Mo6S8 and (La,Ce)Al2, their critical-temperatures (Tc-inv) remain below Kelvin-range, precluding substantial applications. Here, we report field-modulated inverse-superconducting-transitions above 4He-cooling-limit in Eu-based infinite-layer nickelates (EuxNd1-xNiO2 and EuxPr1-xNiO2) grown on a substrate under both overdoped and underdoped regimes. Paradigmatically, superconductivity with zero-resistance is confined between Tc-inv (2.6-5.4 K) and another higher normal-Tc, rising and decreasing with applied magnetic-field, respectively. Starting from the resistive-state below Tc-inv, the inverse-superconducting-transition is driven by not only temperature-rising, but also current-density, while superconductivity further vanishes at higher temperature and current thresholds. The Kelvin-range inverse superconducting transition is plausibly explained by temperature-induced alternating dominance of effective magnetic-fields arising from Eu2+4f7 related compensations relative to the upper-critical-field. Furthermore, an extended-phenomenological-framework is also supported by reemerged superconductivity below 300 mK under magnetic-field, giving rise to an unprecedented temperature-induced reentrant superconductivity. Our findings establish magnetic-interaction-reconfigured high-Tc systems as fertile platforms for exploring quantum phenomena that reverse thermal-decoherence paradigm, also enabling antithetical-designs to unlock untapped application-scenarios for quantum-phase-transition devices.

Antiferromagnetic skyrmions are swirling topological spin textures with rich dynamics and intriguing transport properties, yet their bidirectional dynamics remain largely unexplored. Here, we investigate the dynamics of antiferromagnetic skyrmions driven by current-induced spin-transfer and spin-orbit torques. We computationally demonstrate that antiferromagnetic skyrmions moving in one direction at low current densities can reverse their motion direction when the driving current is above a threshold. Based on the Thiele approach analysis, we show that this bidirectional motion originates from a change in the relative strengths of two effective forces arising from spin-transfer and spin-orbit torques. Furthermore, exploiting this bidirectional motion on a single racetrack, we design programmable logic gates. Our results not only uncover a hidden mechanism for bidirectional skyrmion motion but also facilitate the development of antiferromagnet-based logic devices.

The realization of Coulomb coupled electron-hole double layers in 2D semiconductor heterostructures has enabled the thermodynamic and transport studies of equilibrium exciton fluids without a magnetic field. By doping the exciton fluid with additional electrons/holes, an equilibrium fluid of trions - three particle bound states of electrons and holes - further emerge, providing the platform to explore new transport phenomena associated with such composite particles. Here we report the observation of a Hall effect for trions in MoSe2/WSe2 heterobilayers, which support Coulomb-coupled electron and hole fluids with tunable densities. The Hall effect arises from a Lorentz force on trions under a perpendicular magnetic field. It is manifested in both Hall drag measurements and standard Hall effect measurements on just one of the semiconductor layers. For negatively charged trions, an electron Hall effect is observed even in a hole doped WSe2 monolayer due to the presence of trion drags. The trion Hall effect also disappears when the trions are ionized at elevated temperatures and/or high trion densities. Our work opens the door for realizing quantum oscillations and the quantum Hall effect for trions.

By assuming reversible H-bonding association and dissociation, this work provides a description of the supramolecular structure and dynamics of monohydroxy alcohols (MAs) within the framework of a recently proposed living chain model (LCM). Structurally, reversible H-bonding leads to a single exponential distribution of the molar concentration of the supramolecular chain with length N. Dynamically, reversible H-bonding enables supramolecular chain breakage and recombination, which modifies the relaxation time of the supramolecular chains. In addition to the structural relaxation, tau_a, and the Debye relaxation, tau_D, two other relaxation times are revealed: the chain breakage time, tau_B, and the H-bonding lifetime, tau_H. The interplay among these four-time scales defines five distinct dynamics regimes. In Regimes I and V, no supramolecular chains form. In Regimes II and IV, supramolecular chains form and give a Debye relaxation. The characteristic chain length scales as Nc~tau_D/tau_a. In these two regimes, the H-bonding lifetime controls the Debye process. In Regime III, large supramolecular chains form. In all regimes with supramolecular chain formation, the Debye relaxation comes from the overall chain end-to-end dipole reorientation and scales with Nc. Excellent agreements between experiments and LCM have been observed, leading to quantitative descriptions of the dielectric and linear viscoelastic properties of MAs. These results thus establish a theoretical framework linking reversible H-bonding interactions to supramolecular structures, dynamics, and macroscopic properties of MAs.

Understanding strongly correlated quantum materials remains a central challenge in condensed matter physics and materials science. While angle-resolved photoemission spectroscopy (ARPES) has become an indispensable probe of single-quasiparticle excitations, it accesses electronic correlations only indirectly. Here we show that unlike one-photon in, two-electrons out coincidence ARPES ($γ\!\rightarrow\!2e$ 2eARPES), the two-photon in, two-electron out $2γ\!\rightarrow\!2e$ 2eARPES provides a direct and unambiguous probe of electronic pairing. We establish this on general theoretical grounds and substantiate it through large-scale numerical simulations of strongly correlated models with both paired and unpaired ground states. The key result is a model-independent separation in the $(ω_1,ω_2)$ plane of the two photoelectrons' energies, between signal from electrons emitted from the \emph{same} pair and signal from electrons emitted from \emph{different} pairs; this follows from energy conservation alone and is independent of any material-specific assumptions. Our findings demonstrate that $2γ\!\rightarrow\!2e$ 2eARPES can identify pairing and extract the pair binding energy as well as the energy of the 'glue' boson without any sophisticated data analysis or complementary measurements.

Collinear antiferromagnets with broken time-reversal symmetry have emerged as a fertile platform for spintronics. Using a general tight-binding model and first-principles calculations, we show that strain engineering provides a simple route to control magnetic phase transition and activate transverse responses in representative altermagnets RuO$_2$ and MnF$_2$. For pristine RuO$_2$ and MnF$_2$ with Néel vector $\mathbf{n}\parallel$ [001], symmetry constrains the off-diagonal elements of the Hall conductivity tensor to vanish, thereby forbidding anomalous transport and magneto-optical responses. Shear strain applied along the $ac$ direction preserves the spin symmetry relating the two spin-opposite magnetic sublattices and therefore maintains the altermagnetic phase. By contrast, shear strain applied along the $ab$ direction breaks this spin symmetry and drives a transition from an altermagnetic phase to a partially compensated ferrimagnetic phase in metallic RuO$_2$ and to a fully compensated ferrimagnetic phase in semiconducting MnF$_2$. In addition, the lowered symmetry enables finite anomalous Hall, anomalous Nernst, and anomalous thermal Hall conductivities, as well as magneto-optical rotation angles, which are prohibited in the pristine systems. These responses exhibit a clear strain dependence and become progressively stronger as the strain amplitude increases. Our results establish strain engineering as an effective route to manipulate magnetic phases and functional responses in unconventional antiferromagnets, thereby expanding opportunities for antiferromagnetic spintronics and magneto-optical applications.

Terahertz radiation from $\text{Bi}_2\text{Sr}_2\text{CaCu}_2\text{O}_{8+δ}$ intrinsic Josephson junctions (IJJs) provides an ideal platform to study the synchronization of a macroscopic quantum system. Here, we present a spectral analysis of a frequency-modulated Josephson plasma emitter coupled with patch antennas. In the unmodulated intensity distribution as a function of radiation frequency $I_{\mathrm{UM}}(ω)$, we observe a double Gaussian peak structure. Crucially, double-peak spectra obtained at a constant bias voltage imply either a rapid temporal distribution of resonances or their simultaneous excitation, driven by the mutual electromagnetic coupling between the IJJ mesa and the antennas. At low modulation frequencies $f_m$, the spectra are well reproduced by the products of $I_{\mathrm{UM}}(ω)$ and frequency combs, yielding a synchronized relaxation time $τ_s \simeq 0.28\text{ ns}$. Incorporating $τ_s$ quantitatively reproduces a drastic spectral transformation observed around $f_m \sim 1\text{ GHz}$, unveiling the sub-nanosecond non-equilibrium dynamics of coupled Josephson plasma.

Iron germanium telluride (FGT; FemGenTe2) compounds have attracted significant interest due to their layered van der Waals structure, relatively high Curie temperature, and tunable magnetic properties. Chemical vapor deposition (CVD) is a particularly promising synthesis route owing to its simplicity, low cost, potential for scalability, and widespread adoption in the semiconductor industry, yet it has not been used previously to synthesize FGT with dopants. Here, we report CVD synthesis of both undoped and Ni-doped FGT nanosheets on SiO2/Si substrates. By adjusting precursor molar ratios, we synthesized Ni-doped FGT with multiple Fe concentrations and a 4% Ni-to-Fe ratio. X-ray photoelectron spectroscopy depth profiling further demonstrates that Ni is present in the bulk of the crystals. This straightforward, low-cost, and CMOS-compatible approach demonstrates a route to Ni-doped FGT nanosheets, establishing a foundation for future characterization of Ni-doped FGT and its potential integration into spintronic devices.

The complex Sachdev-Ye-Kitaev (SYK) model, featuring fermions with all-to-all interactions, serves as a dual paradigm for understanding non-Fermi liquid behavior and the holographic nature of charged black holes. Two defining characteristics of the standard SYK model are its maximal chaos (Lyapunov exponent $λ_{\mathrm{L}}=2πT$ at temperature $T$), and its finite zero-temperature residual entropy. While previous studies have largely focused on couplings drawn from a zero-mean Gaussian distribution, we investigate a generalized model with a finite mean-to-standard-deviation ratio, $g\equiv J_{0}/δJ$ of the coupling distribution in order to get deeper insight into the evolution of chaos. We find that increasing $g$ yields the following effects: (i) The system remains a fast scrambler with $λ_{\mathrm{L}}=A~T$, but with a suppressed coefficient $A<2π$. (ii) In the limit $g\to \infty$, out-of-time-ordered correlators (OTOCs) no longer exhibit exponential growth with $λ_{\mathrm{L}}\simeq 0$. (iii) The spectral correlations indicative of late-time chaos maintain Wigner-Dyson level spacing statistics for all values of $g$. (iv) The system preserves a finite residual entropy, albeit with reduced magnitude, for all $g$ values. We conclude that in this generalized SYK model, there is a chaotic to non-chaotic crossover. Moreover different measures of chaos decouple, demonstrating that the presence of finite residual entropy does not strictly imply maximal chaos.

Spin dynamics in ordered magnets with topological lattice defects is investigated. Using fracton--elasticity duality, we develop an effective field theory of magnons coupled to quantized lattice dislocations (dislons) in magnetic insulators. Within this framework, an elastic gauge field mediates a nonlocal interaction between dislocations and magnetization gradients. The resulting magnetoelastic coupling gives rise to coherent magnon-dislon hybridization whose properties are dictated by dislocation topology. Screw dislocations exhibit helicity-selective hybridization and symmetry-protected dark dislon sectors, while edge dislocations generate anisotropic hybrid excitations with finite spin-precession ellipticity through the glide constraint. Our results establish dislocations as dynamical topological defects with directly observable polarization fingerprints in magnon spectra, and reveal magnon-dislon hybridization as a new route to control spin dynamics.

We study the non-equilibrium dynamics of emergent dynamical axion quasiparticles (DAQ) coupled to a photon bath in equilibrium via a Chern-Simons term as a quantum open system. A quantum master equation (QME) is derived up to second order in this coupling implementing only a \emph{partial} Markov approximation, allowing time dependent rates in the Lindblad (QME). These are determined by the equilibrium correlation functions of the Chern-Simons density, and their time dependence allows us to explore transient dynamics in coherences and population: the formation of the quasiparticle on short time scales and its decay, and the build-up of population with an effective time dependent rate. Early time evolution features quantum \emph{anti} Zeno dynamics with enhanced quasiparticle decay and population growth. These phenomena describe transient violations of Fermi's Golden rule and of \emph{detailed balance}, and are distinct \emph{non-Markovian} effects directly related to the spectral density of the Chern-Simons correlators. We obtain the equation of motion of coherent (DAQ) condensates both with the (QME) and with quantum many body linear response establishing a direct bridge between both methods. As a corollary we obtain the expectation value of the Chern-Simons density \emph{induced} by a (DAQ) condensate in linear response, the topological susceptibility is shown to be proportional to the (DAQ) many body self-energy. We provide a Feynman diagram-based interpretation of approximations invoked in the (QME) and corrections from system-bath correlations in higher order.

Recent tunneling measurements on $β$-PdBi$_2$ reported a magnetic field induced phase transition from a fully gapped to a nodal superconducting state. We develop a microscopic theory of superconductivity in this multi-band material, taking into account spin-orbit coupling and Zeeman splitting. We show that there are two attractive pairing channels in this system: an s-wave and a p-wave. At zero magnetic field, s-wave superconductivity wins. At a finite field, this channel becomes less favorable because Fermi surfaces split, and the gap symmetry changes to p-wave. We show that at a higher field, the excitation spectrum of a p-wave multi-band superconductor becomes gapless, with nodal points located in between the split Fermi surfaces. We argue that this behavior accounts for the experimentally observed field-induced nodal superconductivity in $β$-PdBi$_2$.

Twisting layered materials produces moiré superlattices, but prescribed twist angles are usually obtained by demanding assembly procedures. Here we show that montmorillonite, an abundant swelling clay, forms tunable moiré superlattices naturally. Focal-series high-resolution transmission electron microscopy, geometric phase analysis, and molecular dynamics simulation reveal that its apparent rotational disorder is biased toward low-angle misorientations inherited from discrete hydration states. Multilayer stacks preferentially adopt twists near 1-2°, 4°, and 10°, producing long-wavelength moirés without long-range rotational order. We define this kinetically trapped state as a moiré glass, distinct from featureless turbostratic stacking. Simulations indicate that lattice-charge disorder stabilizes the angular preferences, whereas charge ordering promotes random stacking. Hydration screens interlayer interactions and lubricates twist, while dehydration arrests the resulting configurations in discrete steps. These results establish dynamic hydration as a macroscopic handle for programming twist in layered matter.

In a magnetic field bilayer graphene hosts an octet of pseudo-zero-mode electron levels nearly degenerate in orbitals $n=(0,1)$, valleys and spins. They split in valleys by electrostatic gating. In gated bilayer graphene, in which the interlayer bias is set up to flip sign across a line, one has a line junction that traps a portion of pseudo-zero-mode electrons inside the insulating bulk band gap, giving rise to electron states localized along the junction, known as kink states. A close look is made into the spectra and electromagnetic response of such kink states. There are two species of valley current associated with them, a drift current driven by the bias gradient and a circulating current coming from cyclotron motion. It turns out that they both flow in essentially the same direction, with the circulating current exhibiting a magnetic character distinct from those of other higher levels. In equilibrium they spatially circulate within the kink states, creating a quasi-one-dimensional channel of orbital magnetization. The electric control of the orbital magnetization and valley currents via a network of gated junctions will find useful applications in valley electronics.

The first low-temperature electronic transport characterization of individual polycrystalline grains of type-II silicon clathrate (Na$_x$Si$_{136}$, $x \ll 1$), isolated using microfabrication techniques, is reported. Structural characterization via Raman spectroscopy confirms that the isolated grains are largely devoid of amorphous silicon (a-Si). Temperature-dependent resistivity reveals multiple conduction regimes, including thermally activated freeze-out behavior and a transition to low-activation-energy transport at cryogenic temperatures, consistent with hopping conduction mechanisms. Hall measurements from 290 K to 3.5 K yield carrier concentration and mobility trends that correlate with the extracted activation energies, verifying $n$-type conduction. Additionally, gate-dependent conductivity measurements demonstrate electrostatic tunability at room temperature. Collectively, these results establish the magnetotransport parameters of single, isolated grains of type-II silicon clathrate and demonstrate the potential of this material for future quantum and optoelectronic devices.

We develop a minimal hydrodynamic framework to describe exciton transport in the presence of an electron hole plasma in 2D semiconductors. Treating excitons, electrons, and holes as coupled fluids, we show that exciton diffusion is strongly renormalized by momentum exchange with the plasma. In the collisional regime, mutual diffusion leads to a nontrivial redistribution of transport coefficients but preserves the positivity of the exciton diffusivity. In contrast, when plasma inertia and collective charge oscillations are accounted for, the exciton diffusive mode hybridizes with acoustic plasma modes, giving rise to a dynamical instability manifested as an effective negative diffusion coefficient. We demonstrate that this instability originates from the nonequilibrium coupling between slow excitons and fast plasma degrees of freedom, rather than from nonlinear diffusion or thermodynamic effects. Our results provide a unified physical mechanism for negative exciton diffusivity reported in recent experiments and establish collective plasma dynamics as a key control parameter of exciton transport in 2D materials.

The Korringa-Kohn-Rostoker (KKR) Green's function method is a first-principles electronic structure approach well suited to substitutionally disordered alloys through the Coherent Potential Approximation (CPA). AkaiKKR is a widely used implementation, known for efficient treatment of metallic systems and their magnetic properties. Its output, however, is unstructured plain text with no programmatic interface, leaving data extraction entirely to the user and making systematic or high-throughput studies impractical. akaitools is a Python package that parses AkaiKKR output files into structured, type-annotated Python objects. The package covers three output types: self-consistent field (SCF) results, which capture convergence history and per-atom electronic and magnetic properties; spin-resolved, orbital projected density of states for each CPA component; and Bloch spectral functions on a user-defined k-point path. Results come back as immutable dataclasses backed by NumPy arrays. Energy quantities are available in both Rydbergs and electronvolts, and results can be exported to Pandas DataFrames. A built-in plotting module produces Matplotlib figures for DOS curves and SCF convergence. A command-line interface provides file summaries and JSON export without any Python scripting. The package also includes a programmatic input file generator, so full calculation pipelines from input preparation to output analysis can be run in Python.

We address the quantum geometric structure of plasmons in Fermi surfaces enclosing a topological charge. We demonstrate that Weyl fermion plasmons have monopole structure, are topological and have a finite vorticity $ζ=2\mathsf{C}_{\text{w}}$, where $\mathsf{C}_{\text{w}}$ is the Chern number of the Fermi surface enclosing the Weyl point. We show that these plasmons selectively couple to light linearly polarized along the plasmon effective dipole moment $\mathbf{d}$, which has quantum geometric origin and points along the direction of the plasmon center of mass momentum $\hat{\mathbf{Q}}$. We suggest that Weyl metal topological plasmons have distinctive optical properties compared to conventional plasmons.

We present a class of horizonless, regular ultra-compact objects arising in a theory of gravity which allows curvature-fluid coupling. The non-minimal interaction between fluid variables and the Ricci scalar generates a vacuum-like equation of state in the interior, while the exterior remains exactly Schwarzschild. The two spacetimes are glued through a shell at the junction. The interior metric is non-singular, the shell acquires a stiff-matter equation of state, and near-horizon compactness can potentially mimic black-hole phenomenology without event horizons. Unlike the Mazur-Mottola gravastar and its variants, the present model naturally selects a typical ultra-compact mass-radius window, with masses in the range $1.4$-$2.1 M_\odot$ and radii in the range 5-7 km. This framework predicts a unique geometric-thermodynamic shell temperature in the ultra-compact limit distinctly different from the Hawking expression and the other unique observational feature of the model is the prediction of mass independent luminosity.