Papers

Thermal fluctuations can drive an interface when bulk fluctuation amplitudes differ between two phases. We study how shear flow modifies this mechanism using a stochastic non-conserved order- parameter model. For a planar interface parallel to the imposed shear, we derive its propagation velocity in the weak-noise and small-bias regime. The driving force comprises a shear-modified entropic contribution determined by bulk fluctuation spectra and a non-equilibrium contribution arising from the breaking of time-reversal symmetry. At low shear rates, the entropic term provides the dominant contribution to the velocity of an interface near the zero-velocity plane of the shear flow, and the shear-induced change in the velocity scales as the 4/3 power of the shear rate. At high shear rates, two-dimensional simulations show that the measured velocity is largely accounted for by the modified bulk entropic contribution.

We study dissipation driven boundary localization in a Bernevig Hughes Zhang type second order topological insulator by introducing inhomogeneous, spin dependent boundary dissipation. After projection onto the edge subspace, the dominant component of the boundary dissipation lies in the same Pauli channel as the kinetic term. This channel gives both counter-propagating edge modes the same real transfer exponent. The two modes therefore accumulate at the same dissipative domain wall. For the corner states, the dissipative envelope competes with Jackiw Rebbi localization. Increasing dissipation moves their weight from the geometric corners to the dissipative domain wall. Propagating edge states also localize at this wall. Numerical calculations confirm the qualitative predictions of the edge theory. A fixed energy Feshbach reduction captures finite size effects. Inhomogeneous boundary dissipation thus controls boundary state localization without changing the bulk topology.

On-demand sources and mesoscopic beam splitters allow individual ballistic electrons to collide in depleted quantum Hall edge channels, where their unscreened Coulomb interaction acts as a strong, controllable nonlinearity. Theory suggests a more striking possibility: in a strong magnetic field, the same repulsion can drive quantized relative circulation, allowing two electrons to propagate together as a positive-energy Laughlin pair. The relevance of such pairs to experiment depends on lifetimes in realistic guiding potentials and on whether the proposed collision pathway to pair formation survives full two-dimensional dynamics. We develop a microscopic theory of quasibound Laughlin pairs using the physical two-electron Hamiltonian. For a general local electric-field gradient, we determine the dissociation threshold, number of quasibound states, and decay rates. Complex scaling and analytic tunneling theory show that lifetimes grow exponentially with pair energy above threshold. Applied to reported GaAs parameters, the theory indicates that existing devices may already support the lowest spin-polarized pair, with a lifetime estimate roughly two orders of magnitude longer than typical propagation times. We simulate a collision with the full finite-field Hamiltonian, providing both a framework for nonlinear two-electron quantum dynamics and evidence for Laughlin-pair formation in a representative two-electron collision. We use Husimi distributions and their zeros to visualize both quasibound resonances and transient collision states in phase space. These results place the preparation, propagation, and detection of repulsively paired electrons within reach of existing single-electron circuit technology. They identify kinematic stabilization under constrained one-dimensional propagation as a pairing mechanism that may extend to anyonic quantum Hall edge excitations.

We present a multiharmonic lock-in detection approach that utilizes the inverse Fast Fourier Transform to reconstruct the time evolution of thermal susceptibility with high spatial resolution. The method is implemented on a custom-built, modular scanning laser microscope designed for operation in low working-distance optical cryostats and thoroughly calibrated for spatial accuracy. A demonstrative case study using a superconducting resonator highlights the capability of this technique to generate thermal images on time scales significantly shorter than the intrinsic scanning speed, thus enabling dynamic thermal characterization with high spatial fidelity. The proposed technique of low-temperature time-resolved scanning laser microscopy offers unique opportunities to explore superconducting devices, 2D materials, hybrid planar structures, and other low-dimensional systems.

The perpendicular Spin Transfer Torque Magnetic Random Access Memory is one of the most promising emerging non-volatile memory technologies, based on ultra-thin magnetic tunnel junctions. However, as these devices are limited by their thermal stability factor at technological nodes smaller than 20 nm, their scalability is compromised. A possible solution to this limitation relies on taking advantage of the shape anisotropy, by increasing substantially the thickness of the storage layer. Thanks to the combination of a vertical aspect-ratio and enhanced volume, high thermal stability can be maintained at sub-10 nm nodes. Here, we present the technological advancements and understanding of the magnetisation reversal that led to faster switching speeds at reduced switching voltage, providing a viable approach for dense arrays of ultra-small magnetic tunnel junctions.

We introduce an $\mathrm{SO}(3)$-symmetric spin model derived from the algebraic structure of $\mathfrak{so}(3)$: It is obtained as the nearest-neighbor parent Hamiltonian of a Matrix Product State (MPS) built from the generators of the Lie algebra $\mathfrak{so}(3)$ and the identity matrix, and therefore encodes the quadratic relations of the Lie algebra. We characterize the ground space structure of the resulting model and show that for open boundary conditions (OBC), it exhibits a quadratic ground space degeneracy, given by one irreducible representation (irrep) of each odd dimension (integer spin). For periodic boundary conditions (PBC), it has a linear ground space degeneracy, consisting of a singlet — namely, the MPS underlying the model — and a ferromagnet (the irrep with maximal spin), and thus exhibits gapless excitations. We also generalize the construction and the analysis of the OBC ground space to $\mathrm{SO}(d)$ and other compact simple Lie groups. The MPS on which the model is based is an injective MPS, and therefore, its 3-site parent Hamiltonian has a unique ground space and is gapped. The observed critical behavior thus has its origin in the small parent Hamiltonian considered. The model's algebraic ground space scaling thus provides an example distinct from that reported in (Schuch et al., 2025, arXiv:2503.10767), where it was shown that small parent Hamiltonians of injective MPS generically have unique ground states, and examples with an exponential ground space degeneracy were given.

Toroidal order is a higher-rank multipolar order whose intrinsic realization in itinerant-electron systems remains unexplored. Here, we develop a generic theory of the electronic toroidal metal (ETM), in which toroidal order emerges spontaneously from electronic degrees of freedom near the Fermi surfaces. Because candidate toroidal bilinears can overlap by symmetry with the uniform charge current, we formulate a projected instability criterion that removes the noncondensable current component. Within this current-orthogonal sector, we identify a soft collective mode in the $\mathcal{P}$-odd and $\mathcal{T}$-odd particle-hole channel and demonstrate that ETM arises as a Fermi-liquid instability. We then define the toroidal moment in an itinerant system through the antisymmetric magnetoelectric response tensor. We further establish an intimate connection between this response and the topology of pseudospin texture: the rearrangement of pseudospin vortices changes the winding structure of the Fermi surfaces and markedly enhances the magnetoelectric response. ETM also exhibits characteristic nonlinear charge transport, including a pronounced enhancement of its interband quantum-geometric contribution. Our results establish ETM as a distinct metallic Landau phase and provide a general framework for understanding toroidal order generated by itinerant electrons.

Zinc oxide (ZnO), a wide-band-gap semiconductor with mature growth techniques, is a promising host for optically active quantum spins. Yet, optically active quantum defects in ZnO remain largely unexplored. Here, we identify and characterize a family of double substitutional impurities in ZnO, formed by main-group donor-acceptor (DA) pairs, as candidates for optically active quantum defects. Using hybrid density functional theory (DFT), we systematically investigate double substitutional DA complexes and their defect physics, including electronic structure, thermodynamic stability, and optical properties. The proposed defects exhibit isolated defect states, strong spin localization on the acceptor site, and $C_{3v}$ symmetry. Importantly, the electronic structure of the DA pairs is largely determined by the atomic properties of their constituent atoms. We further examine their optical characteristics, including zero-phonon lines (ZPLs), radiative lifetimes, and nonradiative decay to assess their viability as color centers. Notably, among the dimers, (Si$_{Zn}$-B$_O$)$^+$ and (Ge$_{Zn}$-B$_O$)$^+$ exhibit visible optical transitions with sub-microsecond radiative lifetimes and robust charge states against optical ionization, while (Si$_{Zn}$-C$_O$)$^{2+}$ shows the smallest Huang-Rhys factor, approximately 5.6. Our results propose a new family of main-group donor-acceptor defects in ZnO as promising candidates for optically active spin defects.

Carbon-related defects in hexagonal boron nitride are promising room-temperature single-spin qubits and quantum sensors, but their atomic structures remain largely unidentified. Here we show, using first-principles calculations of electron-spin decoherence, that the atomic structure of each defect is imprinted in its spin coherence. Mapping the Hahn-echo dynamics of seven candidate carbon defects across magnetic field and four isotope-engineered nuclear-spin baths, we find that electron-spin-echo envelope modulation emerges at defect-specific magnetic fields, at which the nearest-neighbor nuclear spins satisfy a cancellation condition set by their hyperfine and quadrupole couplings. Both the fields and the modulation frequencies follow from an analytical model using computed hyperfine and quadrupole tensors alone, and they shift or vanish upon isotope substitution. At low fields, the field dependence of the coherence time separates the defects into two classes according to the sublattice occupied by carbon. These decoherence fingerprints, directly testable in isotope-engineered samples, establish a structural identification route complementary to optical spectroscopy.

We study the phase of the coupling between magnons and surface acoustic wave (SAW) phonons in magnetic thin films. The coupling constant changes from a real to a complex number as the external magnetic field is reduced. Below a transition field, the imaginary coupling constant allows SAW phonons to couple to overdamped magnons whose resonance frequency is close to zero and far from the SAW resonance. The strength of the imaginary coupling constant and the magnitude of the transition field both scale with magnetic damping. We find the coupling produces a broad, pronounced minimum in the SAW transmittance spectrum near zero magnetic field in a Ni/Ru/Ni synthetic antiferromagnet with large magnetic damping. These results demonstrate that the phase of the complex magnon-phonon coupling constant can be tuned via magnetic field in strongly damped magnets, offering a platform to explore novel regimes of magnon-phonon interactions.

Mobility links an applied force to the resulting motion and is generally positive near equilibrium. Far from equilibrium, however, internal energy input can reverse this response. Here we show that information feedback provides a distinct route to negative mobility. We consider an overdamped dimer consisting of a run-and-tumble particle coupled by a spring to a passive Brownian particle. Information enters through periodic measurements of the relative displacement, which are processed to reset the active polarity. Although the unloaded dimer has no net drift, an applied force biases its internal configuration, and an information-mechanical feedback amplifies and converts this bias into active propulsion against the force, producing negative mobility. We develop an analytical theory that captures this mechanism and yields a feedback-gain criterion for response reversal. Including the information-processing cost reveals a tradeoff: rapid feedback enhances reverse transport but incurs a growing informational cost, yielding an optimal finite feedback rate for information-inclusive efficiency. These results show that information can reshape nonequilibrium response by controlling how internally supplied energy is converted into macroscopic transport.

Nanofluidic memristors, exploiting ion transport in nanochannels, hold promise for neuromorphic applications. A planar architecture is particularly desired for scalable integration with established micro- and nanofabrication technologies. Here, using the Poisson-Nernst-Planck framework, we theoretically propose planar nanofluidic memristors enabled by surface charge gradient, providing an alternative to the commonly used geometrically asymmetric architectures. The resulting memristive behavior is governed by a diffusion-mediated secondary enrichment effect. By systematically solving the PNP equations, we obtain the scaling of the characteristic memory time across the parameter space. We also reveal that the memory effect is related to the first-order moment of surface charge, for arbitrary charge profiles. These results provide a theoretical basis for rationally designing and optimizing planar nanofluidic memristors through spatially patterned surface charge.

Quantum wake dynamics in quantum magnets have recently been inferred from the dynamical spin structure factor, which probes only a restricted class of local perturbations. Here, we show that resonant inelastic x-ray scattering (RIXS) selection rules act as an operator filter on fractionalized excitations, producing distinct quantum wakes in the spin-$\frac{1}{2}$ Heisenberg antiferromagnetic chain. Using explicit real-time evolution of single-spin and spin-conserving bond correlators, we find that the conventional spin response propagates up to the maximum spinon velocity, $v_s=\frac{\pi}{2} J$, whereas the bond channels concentrate their spectral weight into a slower dominant wake with $v\simeq 0.92 J$, while weaker components remain bounded by the full spinon light cone. The corresponding momentum- and frequency-resolved responses map onto experimentally accessible RIXS channels, demonstrating that different spectroscopic perturbations resolve complementary pathways of many-body propagation beyond the neutron-scattering spin structure factor. Their inelastic spectral weights further provide access to quantum Fisher information, while equal-time bond sum rules connect the same spectroscopic channels to the ground-state energy. Because the same correlators can be prepared and measured on quantum hardware, they also define direct, experimentally anchored benchmarks for quantum simulations, particularly in frustrated and higher-dimensional magnets where controlled classical real-time calculations become challenging.

We present a comprehensive Monte Carlo study of two-dimensional bond percolation with algebraically decaying connection probabilities $p(r)\propto 1/r^{2+\sigma}$, establishing the universality diagram in the long-range (LR) regime for $\sigma\le2$. Using the event-based ensemble method, we simulate systems with linear sizes up to $L=16384$ and investigate three universality regimes: LR Wilson–Fisher (WF) A ($1<\sigma\le2$), LR Wilson–Fisher B ($2/3<\sigma\le1$), and LR mean-field (MF) ($0<\sigma\le2/3$). In the LR-WF-B regime, the anomalous dimension is consistent with $\eta=2-\sigma$, in agreement with mathematical results for $2/3<\sigma<1$, while the correlation-length exponent $\nu(\sigma)$ exhibits nontrivial, non-Gaussian variation. In the LR-WF-A regime, although $\eta$ remains close to $2-\sigma$ for smaller $\sigma$, statistically resolvable deviations $\delta\eta(\sigma)=\eta-(2-\sigma)>0$ start to appear near $\sigma\simeq3/2$ and grow toward the short-range crossover at $\sigma=2$. Finally, by complementing the event-based simulations with conventional ensemble simulations, we reveal the coexistence of complete-graph asymptotics and LR Gaussian-fixed-point scaling in the LR-MF regime. These results further clarify the critical properties in long-range percolation and provide crucial benchmarks for long-range statistical systems.

In anisotropic optical media, the electromagnetic response depends on the orientation of the optical field relative to the material's principal dielectric axes. While this direction dependence is well understood in conventional optics, it should also influence light-generation processes driven by free electrons. Here, we experimentally observe spectrally anisotropic transition radiation from biaxial van der Waals crystals. Using cathodoluminescence spectroscopy on germanium sulphide (GeS) and molybdenum oxydichloride (MoOCl$_2$) crystals, we show that the transition-radiation spectra differ along the principal in-plane optical axes. To describe this spectral anisotropy, we develop a thin-film transition-radiation model that reproduces the experimental observations. Our results demonstrate that transition radiation is a sensitive probe of the axis-dependent dielectric response of biaxial optical media and suggest that optical anisotropy can provide an additional degree of freedom for free electron-driven spectroscopy, radiation sources, and transition-radiation-based diagnostics.

Under non-equilibrium conditions, energy/particle currents flow through a quantum system coupled to multiple baths. Although the fluxes increase in the weak coupling regime as the coupling strengthens, the reason why they decrease to zero for large coupling remains unknown. This counterintuitive behavior of energy exchange or transport phenomena is called the turnover effect. It has been predicted in several quantum systems such as photosynthetic complexes, mesoscopic junctions, quantum heat machines, and chemical networks without a single counterexample, and it results in constrained performance due to limited currents. Here, we use scattering theory to study the turnover effect produced by low-zdensity reservoirs of free particles scattered by a quantum system through localized potentials. We find that the turnover effect is a consequence of total reflection that impedes the reservoir particle from reaching the interaction region and exchanging energy with the quantum system. Moreover, we design a protocol based on quantum tunneling to avoid the turnover and to increase the maximum current. This strategy could be used to unleash the full potential of devices based on temperature/chemical potential gradients.

Nonlinear Hall effects provide a powerful probe of quantum geometry in solids and enable rectification phenomena beyond the constraints of linear response. In this Letter, we predict a layer nonlinear Hall effect (LNHE) in stacked bilayer systems composed of nonmagnetic or antiferromagnetic materials with a vanishing linear Hall conductivity. In such systems, the second- or third-order nonlinear Hall responses are intrinsically layer odd: the contributions from the two constituent layers have equal magnitude but opposite sign, resulting in exact cancellation under layer-exchange symmetry. An out-of-plane electric field $E_z$ can break this symmetry, thereby unveiling the hidden response and converting it into a switchable macroscopic nonlinear Hall signal. Using a minimal $k\!\cdot\!p$ model, we demonstrate that the LNHE can originate from the Berry curvature dipole mechanism. A systematic symmetry analysis of all 80 layer groups further yields a complete classification of the symmetry constraints and stacking configurations that allow for this type of LNHE. Beyond this mechanism, additional symmetry analysis reveals that LNHE may also arise from quantum metric dipole or inversed mass dipole. Remarkably, even in cases where second-order nonlinear Hall responses are symmetry forbidden, a third-order LNHE can still survive in certain stacked bilayer configurations. First-principles calculations on representative bilayers—nonmagnetic 1T$'$-WTe$_2$ and 1T$'$-ReS$_2$—explicitly demonstrate electrically reversible second-order LNHE, in full agreement with our symmetry-based predictions. Overall, our results establish LNHE as a universal phenomenon in a wide range of layered quantum materials and provide a robust route toward electrically tunable nonlinear transport.

We construct representation-independent families of solutions of the non-braided scalene Yang–Baxter equation from quadratic noncommutative algebras. Beginning with two anticommuting generators, we obtain a continuous deformation in terms of quantum-plane algebras and extend the construction to an arbitrary number of generators. In the latter case the scalene Yang–Baxter relation fixes the multiparameter exchange matrix to an exact multiplicative form, thereby selecting a distinguished subclass of multiparameter quantum affine spaces. We construct finite-dimensional realizations using singular matrices and finite Heisenberg–Weyl operators, as well as infinite-dimensional realizations in terms of bilateral weighted shifts and multiplicative-shift operators. The explicit realizations are generically purely scalene: although the ordered triple satisfies the scalene Yang–Baxter equation, its individual constituent operators do not satisfy the ordinary non-braided Yang–Baxter equation. These results provide a representation-independent algebraic framework for constructing Yang–Baxter-irreducible scalene triples and a starting point for investigating their possible applications to quantum integrability.

Conventional field selection of magnetic order relies on the Zeeman coupling, which, however, vanishes in magnets without net magnetization, a rapidly growing class including altermagnets (AMs), noncollinear antiferromagnets (nc-AFMs), and PT-symmetric antiferromagnets (PT-AFMs). Here we show that the quantity that fundamentally couples a magnet to a uniform magnetic field is not the magnetization, but the binary order parameter eta that labels the two time-reversal-related minima of the Landau free energy. We develop a Landau theory of order selection based on eta under the constraints of magnetic point-group (MPG) symmetry, in which eta couples to odd-degree polynomials in the magnetic field. Within this framework, the linear term is the ferromagnetic Zeeman coupling, while higher-order couplings with leading degree n = 3, 5, 7, and 9 naturally appear in AMs and nc-AFMs. In contrast, combined PT symmetry forbids any such coupling. Consequently, it is the order-(n-1) magnetic susceptibility, rather than the net magnetization, that serves as the primary experimental observable for identifying the magnetic order of AMs and nc-AFMs. For all 122 MPGs, we classify the leading coupling degree and the corresponding polynomial forms. We demonstrate our framework in two representative materials: the AM MnF2 and the nc-AFM MnTe2. We further construct a symmetry-allowed spin model for an AM system to reveal the microscopic origin of the higher-order coupling and establish the coupling coefficient explicitly in terms of the spin-model parameters. Our work unifies the description of magnetic-order selection across magnets with and without net magnetization, offers a microscopic origin for this counterintuitive physics, and provides fingerprints for distinguishing intrinsic field selection from extrinsic switching.

Altermagnets have attracted intensive attention recently, owing to their unique combination of zero net magnetic moment of antiferromagnets and momentum space spin-splitting of ferromagnets. Herein, we systematically explore monolayer altermagnetic Ti$_2$XX' (X/X' = F, Cl, Br, I) materials for novel electronic properties. Especifically, spin-splitting exists in the valence bands of all studied materials, whereas several compositions exhibit nearly spin-degenerate conduction bands near the Fermi level, which is markedly different from conventional altermagnets. This phenomenon can be attributed to the bond-angle-sensitive super-exchange occurring in the $d_{xz}$ or $d_{yz}$ orbitals, while the super-exchange of the $d_{x^2-y^2}$ orbital is not sensitive to the Ti-X-Ti bond angle. Motivated by this intriguing phenomenon, Fermi level modulation via doping or heterostructure construction enables the transition between two electronic states, endowing these materials great application potential in information storage devices.

Recent quantum twisting microscopy experiments [1] have provided unprecedented momentum- and energy-resolved imaging of magic-angle twisted bilayer graphene, revealing a stark dichotomy between the heavy and light electronic characters of its narrow bands. In this work, we provide a sharp distinguishing criterion between the two most likely candidate states that exhibit spectroscopic features consistent with the experimental results. Focusing on charge neutrality, these states are 1) the 'Mott semimetal', governed by strong dynamical correlations, and 2) the 'strain-induced anisotropic semimetal', characterized by weak Hartree-Fock effects. We demonstrate that an out-of- plane magnetic field serves as a sharp discriminating probe based on the expected Landau level gap size hierarchy. We find that the strain-induced anisotropic semimetal has a robust gap hierarchy where the Chern C gaps, \Delta_C , decrease in order \Delta_{\pm 4} > \Delta_{\pm 8} > \Delta_{\pm 12}. In contrast, for the Mott semimetal, \Delta_{\pm 4} remains the largest gap, while the relative magnitude of the C = \pm 8, \pm 12 gaps depends sensitively on the applied magnetic field. We test the robustness of these results against strain orientation and lattice relaxation finding consistency between the gap hierarchy of the strained semimetal and previous incompressibility measurements at finite magnetic field [2].

We investigate the Lee–Yang zeros (LYZ) of inhomogeneous anisotropic XY spin chains with Dzyaloshinskii–Moriya (DM) interactions in the complex transverse-field plane, focusing on their fundamental connection to quantum phase transitions. We systematically study uniform chains, period-2 and period-3 modulated chains, and Fibonacci quasiperiodic chains of lengths 5 and 8. As the DM coupling strength $D$ increases, the LYZ exhibit qualitatively distinct topological evolutions on the complex plane: the complex zeros of the uniform chain collapse toward the real axis; periodic chains feature either bifurcation of closed zero contours before all zeros become real or a single re-emergence of complex zeros; quasiperiodic chains exhibit repeated annihilation and revival of complex zeros. Analytical derivations demonstrate that this diverse behavior originates from DM-induced shifts of folded bands and the modulation of zero positions by anisotropic pairing at particle–hole band crossings. Our results establish a direct correspondence between LYZ topology and band deformation: isolated contact points of zeros with the real axis correspond to discrete quantum critical fields, while continuous real-zero intervals directly identify gapless chiral phases. Accordingly, beyond locating phase boundaries, LYZ can distinguish characteristic phases and serve as an intuitive probe for band folding and phase diagram restructuring.

A power series for the Wigner-Kirkwood pair commutation function for quantum statistical mechanics in classical phase space is given with terms automatically generated by recursion. The calculated second virial coefficient agrees with the measured values of helium for temperatures greater than 65 K. Prospects for a general quantum Monte Carlo algorithm are discussed.

We determine the aging phase diagram of mixed spherical $(p+s)$-spin glasses quenched from random configurations to zero temperature. Solving the asymptotic dynamical equations of Cugliandolo and Kurchan, we find transitions between aging states with one, two, and continuously many effective temperatures, including phases in which discrete and continuous hierarchies coexist. We obtain analytic expressions for the energies reached asymptotically by the dynamics. In models combining pairwise and higher-order interactions, and sufficiently separated interaction orders ($s>3$), a fully continuous phase exists, where the gradient descent relaxation converges to the algorithmic energy lower bound. Instead, in mixed models with only high-order interactions ($p\ge3$) the energy relaxation remains strictly above it. Numerical integration of the dynamical equations is consistent with the predicted two-step and mixed discrete–continuous aging states.

We study phase transitions out of a (2+1)d topological phase driven by the proliferation of anyons in a braided fusion subcategory. We describe a general theoretical framework for such transitions, in which the topological quantum field theory (TQFT) is coupled to dynamical matter associated with anyons in the subcategory. We interpret this construction using symmetry topological field theory (SymTFT), where the dynamics is localized on the symmetry boundary of the (3+1)d slab. We analyze several examples, and present explicit Chern-Simons-Higgs (CSH) field theories realizing the proliferation transitions. We also examine proliferation transitions that implement gauging of non-invertible one-form symmetry in the parent TQFT. This includes a general construction for ${\rm Rep}(G)$ one-form symmetry for a finite group $G$, and a CSH realization of the non-invertible one-form gauging ${\rm SU}(2)_{10}\rightarrow {\rm Spin}(5)_1$. We discuss which anyons proliferate at these transitions.

Early thinking in the field of high entropy oxides (HEOs) emphasized their likely abundance, with combinatorial arguments hinting at a myriad of new materials. The experimental reality has proven more challenging: the stability of HEOs cannot be straightforwardly predicted based on ionic radii, lattice geometry, and charge-balancing considerations alone. In this work, we employ machine learning interatomic potentials (MLIPs) to predict the synthesizability of HEOs of the form $A_2$O$_3$ derived from a selection of trivalent cations. From nearly 500 possible compositions, we identify 16 promising candidates for experimental validation with solid-state and combustion synthesis. We discover three new HEOs in the corundum structure, including (Al,Cr,Fe,Rh,Sc)$_2$O$_3$, and one novel cation-ordered phase, (Al,Fe,Ga,Sc)$_2$O$_3$. By far the most common synthesis outcome was a mixture of competing phases, sometimes involving redox reactions. Our results also reveal profound synthesis method dependence for the final product, where qualitatively equivalent outcomes between the two synthesis methods were only observed for 3 of the 16 tested compositions. We conclude that the occurrence rate of HEOs is far rarer than initially believed and that machine learning approaches can effectively guide us to the "needle in the haystack".

The quantum Hopfield model is widely used to describe ultrastrong light–matter coupling between cavity photons and collective bosonic excitations in solids, where the diamagnetic interaction is conventionally assumed to be a constant. We experimentally demonstrate that the diamagnetic response of Landau polaritons is reduced under strong terahertz field excitation. We show that this behavior originates from field-driven redistribution of electrons into the nonparabolic regime of the conduction band of GaAs, which reduces the plasma frequency and consequently the diamagnetic interaction strength. A microscopic hot-electron model reproduces the observed nonlinear response. Motivated by this microscopic picture, we propose a nonlinear extension of the Hopfield model with a Kerr-like interaction. Our results establish a route toward nonlinear cavity quantum electrodynamics and driven ultrastrong light–matter coupling beyond the conventional linear Hopfield description, which is capable of creating uniquely quantum optical effects such as squeezed light generation.

The fabrication of highly ordered laser-induced periodic surface structures (LIPSS) on thin metallic films is dictated, predomaninatly, by a synergy of periodic electromagnetic energy deposition and complex fluid dynamics. In this work, we present a combined experimental and theoretical study on the formation of ultra-regular LIPSS on 32-nm-thick Au films using a double-pulse femtosecond laser scheme. We demonstrate that for thin films, the excitation of coupled Surface Plasmon Polaritons (SPPs) at both interfaces dictates the initial energy distribution. On the othe hand, the final morphology is greatly influenced by hydrodynamical processes. Interestingly, due to the low electron-phonon coupling of Au and the high thermal confinement of the thin film, single-pulse irradiation leads to uncontrolled hydrodynamic instabilities a non uniform topographies. Thus, we demonstrate that a double-pulse approach with an optimized interpulse delay ({\Delta}{\tau}=1.2 ns) effectively controls the melt duration and viscosity, suppressing complex fluid motion and promoting the growth of highly ordered arrays. These structures support narrow surface lattice resonances (SLRs) suitable for high-sensitivity plasmonic biosensing.

AutoMOOSE is an agentic software framework that converts a natural-language request into an executed, screened, and interpreted MOOSE phase-field simulation. Here, we deploy AutoMOOSE as a agentic software, complementing our prior work which focused on development of the agentic tool. We describe our software framework and architecture through Use Case and logical views of the 1+5 architectural-views model, covering its user roles, component structure, six-agent pipeline, physics plugin layer, Model Context Protocol interface, and screening/falsification/recovery loop. Our architecture separates physical falsification from automatic repair, so corrected simulations remain inspectable and must be re-admitted before acceptance. We focus on software design, extensibility, interoperability, and reuse of the AutoMoose framework for broad utilization in multiphysics materials design problems.

Two-dimensional topological materials with Mexican-hat dispersion exhibit numerous nontrivial features, such as double-valued isoenergetic contours in k-space, strong mixing of electron and hole states, a van Hove singularity in the density of states, and specific quantum geometric properties. We find that, due to these features, Mexican-hat dispersion significantly strengthens interband plasmons, reduces their damping, and gives rise to an additional branch of the plasmon spectrum when electron-hole symmetry is broken. The plasmon spectra are limited to a finite range of the wave vector, the boundaries of which depend on the strength of the electron-electron interaction. We also reveal a relationship between the features of the plasmon spectrum and singularities of the joint density of states with a finite plasmon wave vector q, as well as features of the interband quantum metric, which also depend on q.