Papers

Kikuchi lines and bands in reflection high-energy electron diffraction (RHEED) carry information on crystal geometry and electron scattering, but are often obscured by intense diffraction streaks. We combine multiscale convolution with spatial detail from skip connections and independent supervision that allows overlapping regions to localize streaks and candidate Kikuchi regions separately. Using manual polygon annotations made before model-assisted editing, the Kikuchi intersection-over-union (IoU) on 29 laboratory test images from separate growth batches was $0.6290 \pm 0.0137$. We then performed supervised adaptation to public chalcogenide images and stratified images by Kikuchi visibility using the median ratings of three observers who rated the images separately, two of whom rated with predictions hidden. With all 244 training images, IoU for the clear-feature group of 10 test images was $0.5014 \pm 0.0336$, whereas ambiguous images gave lower values. With 100 training images, clear-group IoU was $0.5171 \pm 0.0073$; expanding the training set also reduced responses on images without target features. Reported uncertainties are sample standard deviations across four laboratory runs or three adaptation runs. Public-image adaptation used reference masks of mixed provenance, including prediction-derived drafts. The method converts visual cues into inspectable spatial regions, providing a basis for analysis of line positions, intersections, and local intensity.

Low-dimensional magnetic systems have received significant interest due to their high scalability and energy efficiency for future electromagnetic applications. However, low-dimensional magnetism at finite temperature is subject to Mermin-Wagner fluctuations, which make its realization highly challenging. Here, we propose structural modulation in the thin-film structure of an orthoferrite system to achieve a high low-dimensional magnetic response at room temperature. ErFeO3 epitaxial thin film with atomically precise thickness control demonstrates that the magnetic response at 300 K can be significantly enhanced compared to its bulk counterpart. The magnetic response reaches its maximum value of 3.7 MuB/f.u. for the 2 nm-thick epitaxial film. The characteristic domain structure resulting from epitaxial strain and orbital reconstruction at the surface, both arising from the thin film geometry, has been proposed as the microscopic origin of the giant magnetization enhancement. We show that magnetic ordering can indeed be realized in the 2D limit, with deliberate structural control of orthoferrite systems.

Interlayer coupling controls the electronic properties of layered van der Waals transition metal dichalcogenides. We investigate light-induced control of the interlayer spacing through orbital-selective excitation in trilayer 1T'-WSe2 and 1T'-WS2. Real-time time-dependent density functional theory simulations show that the interlayer spacing contracts or expands depending on whether chalcogen p-orbital density is depleted from or accumulated in the interlayer region. Effective Lindblad models coupled to the lattice dynamics reproduce these contrasting responses with simplified dynamics. A single effective excited state captures the cosine-like displacive motion in trilayer 1T'-WSe2, whereas the shift of the equilibrium spacing in trilayer 1T'-WS2 requires two excited states with different electron-phonon couplings and relaxation channels. Static calculations at varied interlayer spacings indicate that these spacing changes modify the electronic gaps and could access different electronic phases. These results connect orbital redistribution, carrier relaxation, and interlayer breathing motion, and establish orbital-selective optical excitation as a route to tuning the electronic properties of layered materials.

Spin–orbit torque MRAM (SOT-MRAM) is a leading candidate for next-generation nonvolatile memory, offering high speed, endurance, and architectural compatibility. However, in conventional SOT switching, the magnetization remains near the in-plane region at pulse termination, making the final state highly sensitive to post-pulse relaxation dynamics and prone to back-switching. To overcome this, we propose a field-free scheme in which the transverse SOT drives large-angle precessional excitation while the perpendicular spin-transfer torque (STT) biases the trajectory toward the reversed $-z$ state. Micromagnetic simulations reveal a nonlinear switching boundary in the $J_{\mathrm{STT}}$–$J_{\mathrm{SOT}}$ parameter space, originating from the distinct dynamical roles of the two torques: SOT primarily governs the excitation and crossing of the dynamical separatrix, whereas STT controls the terminal trajectory and final-state selection. An analytical macrospin model, based on the stability analysis of the current-induced equilibrium, reproduces the critical-boundary trends as functions of current density, Gilbert damping $\alpha$, and uniaxial anisotropy $K_\mathrm{u}$, and distinguishes dynamic anti-damping and static instability branches. Systematic analyses of pulse duration, damping, anisotropy, and the STT–SOT balance further demonstrate that reliable ultrafast switching requires not only sufficient excitation to cross the separatrix before pulse termination, but also precise control of the pulse-end magnetization state to minimize post-pulse relaxation. These results establish that the pulse-end state, rather than the instantaneous torque amplitude, is the decisive factor governing switching speed and reliability in coupled STT–SOT systems.

By including spatially varying volume fractions of the constituents, composites are obtained that are akin to functionally graded media. An extension of the mathematical apparatus of double groupoids is proposed to incorporate these materials with the aim of eventually classifying defects of misalignment and their time evolution.

Building on the Bethe ansatz and generalized hydrodynamics, we rigorously establish universal relations between Drude weights governing charge, spin, and energy transport and thermodynamic properties for the one-dimensional repulsive two-component continuum Fermi gas - the paradigmatic integrable Yang-Gaudin model. We analytically derive thermodynamic expressions for charge Drude weights: $D_{nn}$, $D_{nm}$, $D_{ne}$ (responses of particle, magnetization and energy currents to a chemical potential gradient) equal the particle density, magnetization, and temperature times entropy density, respectively. These relations constitute a hallmark of ballistic transport, and can be generalized to other 1D continuum integrable systems. Furthermore, we investigate spin Drude weight ($D_{mm}$, $D_{me}$) at zero and low temperatures. They characterize the magnetization and energy current responses to a magnetic field gradient, revealing an essential spin-charge coupling feature in quantum transport. We find that the Drude weights $D_{nm}$, $D_{mm}$, and $D_{me}$ across the $\mu\text{-}H$ plane remarkably map out the zero-temperature phase boundary. This work fills a critical gap in the understanding of transport within integrable quantum gases and furnishes a direct theoretical foundation for future ultracold-atom experiments.

Emergent phenomena in quantum materials arise from interactions among different degrees of freedom. Identifying these interactions and establishing their roles in ordered states are central problems in condensed-matter physics and provide a basis for controlling material properties. Many relevant low-energy excitations and gaps lie in the terahertz (THz) and mid-infrared (MIR) range, where intense phase-stable fields can both interrogate nonlinear dynamics and drive selected degrees of freedom far from equilibrium. This review surveys recent progress in probing and manipulating quantum materials with strong-field THz and MIR radiation, with emphasis on nonlinear electronic dynamics, collective-mode coupling, symmetry-sensitive responses and field-induced changes in electronic structure and ordered states. Particular attention is given to developments enabled by the Synergetic Extreme Condition User Facility (SECUF).

Understanding the dynamics of interacting quantum fields remains a fundamental challenge. We propose a superconducting transmission line for analog quantum simulation of $(1+1)$-dimensional $\phi^4$ field theory. The transmission line comprises fluxonium-like circuit elements whose continuous and unbounded phase variables encode a scalar field without Hilbert-space truncation. Their anharmonic potentials provide strong interactions. Tuning the circuit parameters provides access to two distinct regimes. In the first, the transmission line emulates $\phi^4$ field theory with a single-well potential. We confirm this correspondence through lattice Monte Carlo calculations of the low-energy spectra of both the circuit and lattice $\phi^4$ theory. This regime enables scattering experiments between counter-propagating particle wave packets. The second parameter set yields a double-well potential that emulates $\phi^4$ theory in the symmetry-broken phase and hosts degenerate vacua. Interfaces between the two vacua form topological kinks, and the transmission line can simulate kink-antikink collisions. We present state preparation and measurement protocols for both collision experiments, enabling spatially resolved, real-time studies of particle and soliton scattering in an interacting quantum field theory.

We present a high-resolution numerical study of the spin-1 Blume–Capel ferromagnet on the honeycomb lattice ($z=3$). Wang–Landau estimates of the joint density of states $\Omega(E_1,E_2)$, combined with field mixing, are used to map the first-order transition line and locate the tricritical point at $(\Delta_t,T_t)=[1.4819(2),\,0.4022(7)]$. Histogram reweighting of Metropolis simulations for $L=36$ and $48$ provides an independent consistency check, with a crossing temperature near $0.4039$, compatible with the Wang–Landau extrapolation. From the field-mixing analysis we obtain $r=-1.586(19)$, while the slope of the multicanonical coexistence line yields the consistent and more precise estimate $r=-1.587(5)$. Normalizing by the zero-temperature field $\Delta_0=zJ/2$, the available honeycomb, square, triangular, and simple-cubic estimates cluster near $r/\Delta_0\simeq-1.06$, corresponding to a magnitude about $6\%$ larger than the mean-field value $-1$; no systematic dependence on coordination number or dimensionality is resolved over the range examined. Finite-size scaling of $\sigma_Q$ gives $y_t=1.795(7)$, consistent with the tricritical Ising value $9/5$, while the fourth-order cumulant scaling is compatible with $y_g=4/5$. Deep in the first-order regime, the cumulant approaches the expected two-phase limit $U_Q\to2/3$. Multicanonical simulations up to $L=64$, using weights constructed directly from the Wang–Landau density of states for $L\le24$ and rescaled and refined for larger systems, yield an interface-tension exponent $\mu=1.265(26)$, consistent with the tricritical prediction $(d-1)/y_g=5/4$. Finally, we map the continuous branch of the phase boundary from the same density-of-states data, obtaining $T_c(\Delta=0)=1.157$; estimates sufficiently close to the tricritical point are affected by crossover from Ising to tricritical scaling.

MXene properties are typically tuned through composition, surface termination, and intercalation, while the metal-carbon framework topology is considered fixed. Here, we demonstrate that this framework can reconstruct. Unconstrained relaxations of biaxially strained bare Ti3C2 yield a dynamically stable polymorph, N, featuring a 15-atom primitive cell, six distinct Ti-C bond classes, and 2.55 Å Ti-Ti pairs. The coherent transformation pathway crosses an 8.47 eV barrier per cell but first reaches another reconstructed minimum, N', lying 1.08 eV below N, revealing a family of bond-switched networks. Phase N lies 7.58 eV per cell above the parent. Reverse barriers along the calculated pathway are 1.50 and 1.98 eV per cell for N and N', respectively. Reconstruction quenches the parent spin polarization, yielding a nonmagnetic metal with a nearly fourfold increase in Fermi-level density of states. Bader and electron-localization analyses suggest charge redistribution from C toward Ti associated with Ti-Ti pairing. In multilayers, reconstructed layers form interlayer Ti-C bonds. A 10% biaxial tension halves the phase-energy difference, and pressure reverses phase ordering near 85 GPa. These results establish bond-switching reconstruction as a mechanically controllable structural degree of freedom in MXenes.

Increasing miniaturization of nanoscale devices makes determining the three-dimensional distribution of dopants increasingly important. In out-of-focus spectroscopic scanning transmission electron microscopy images, we show that dopant atoms appear as disks with radii relating to dopant depth, allowing the three-dimensional distribution of dopants to be determined from simple geometric analysis of a single out-of-focus image. Through numerical experiments on Si-doped graphene we validate statistical detection and Bayesian inference methods to quantify confidence and uncertainties while making the analysis more robust at lower dose. We present proof-of-concept experimental data from an Fe-doped spinel, retrieving dopant depth to within around 2 nanometres.

We study general maximal hard-core models on periodic lattice-type graphs. While for standard models, phase coexistence may arise for high activity, for maximal models this behavior may occur also for sufficiently low activity values. Relying on the concept of volume allocation, we develop a unified set of assumptions that imply the Peierls condition, a convergent cluster expansion for the partition function, and hence the conclusions of Pirogov-Sinai theory for this class of models. We further check these assumptions for a number of examples including standard lattice-type periodic graphs, proving crystallization for both high and low activity. We also derive estimates for the values of activity that bound the phase coexistence regions in the phase diagram, rewriting for this purpose the proof of a technical result in the derivation of Pirogov-Sinai theory.

Dipolar quantum gases in elongated traps become supersolid through a transition that is continuous at intermediate density but first order at low and high density; at the continuous point, ramps of the scattering length follow Kibble–Zurek scaling. We study ramps across the first-order superfluid–supersolid transition of $^{164}$Dy in an infinite tube using the three-dimensional extended Gross–Pitaevskii equation with truncated-Wigner noise. With quantum noise only, the uniform superfluid survives the metastable window and transforms after its spinodal, where the roton softens. For onsets occurring during the linear ramp, the delay measured from this spinodal has a fitted exponent $\zeta = 0.36 \pm 0.02$, close to the continuous-transition result and the mean-field value $1/3$. Reverse ramps show a comparable delay beyond the fold of the crystal branch, producing dynamical hysteresis. Initial thermal noise with nominal temperatures of 2.5–10 nK produces crystalline regions inside the metastable window during holds, with faster nucleation closer to the spinodal and at higher initial temperature. In ramps at 5 nK, thermal fluctuations cross onset thresholds near $f_s = 1$ early, whereas the bulk of the crystal still forms after the zero-temperature spinodal with a similar scaling. Without a heat bath these effective rates depend on preparation: ramps crossing the window at the same rate nucleate early in 2 of 32 or 11 of 16 realizations depending on their starting point. At low density, slower ramps select larger spacings in a crystal of separated droplets, and droplets survive far above the transition on reverse ramps. A Maxwell construction gives a coexistence window $0.04 a_0$ wide around the first-order transition point, in which localized states exist; in the simulated tube they lie above the homogeneous states. At the continuous point there is no coexistence.

The $^{229}$Th nuclear clock transition is inhomogeneously broadened even at sites of nominally cubic symmetry, where the electric-field gradient of the ideal lattice vanishes. We show that dilute static point-defect disorder produces a doublet with a zero at the quadrupole-free frequency. The doublet is symmetric in the isotropic approximation; size misfit point defects introduce a small lobe asymmetry without removing the zero. Charged and size-misfit defects share inverse-cube scaling and an approximately common normalized profile, whose width separates into a host-controlled background and a term linear in the $^{229}$Th density. In a heavily doped $^{229}$Th:CaF$_2$ crystal [Nature 657, 626 (2026)], the thorium-linked contribution is comparable to the measured 1.1 MHz width; in a lightly doped crystal [arXiv:2606.08870], the 0.9 MHz width bounds the host background. Neither spectrum shows the predicted dip, which points to the presence of extended defects in both crystals. If the predicted dip is resolved, it can provide a nuclear-clock discriminator referenced to the quadrupole-free nuclear transition frequency.

Finite photon momentum allows second-order photocurrents in centrosymmetric space groups, where the conventional bulk photovoltaic effect is forbidden. Here we study the photon-drag response of altermagnets and show that its angular dependence reveals both the symmetry of the magnetic order and the Néel domain of the sample. For example, when a crystal rotation exchanges the two domains, the domain-even and domain-odd parts of the current appear in different angular harmonics, $4n$ and $4n+2$ for tetragonal $d$-wave altermagnets, so that two measurements rotated by $90^\circ$ on a single domain isolate the domain-odd current. We also find that these microscopic contributions exhibit opposite domain parities depending on light polarization. Under linear light, only the shift term is domain odd, while under circular light, the domain-odd channel switches to the injection, Fermi-surface, and contact principal-value terms. Mirror symmetries fix the angular phase of each harmonic and distinguish $d_{x^2-y^2}$, $d_{xy}$, and $g$-wave order. In contrast, conventional collinear antiferromagnets show no domain-odd photon-drag current, and in tetragonal ferromagnets the two parts share the same harmonics. Although the altermagnetic spin splitting does not require spin-orbit coupling (SOC), SOC is essential to observe the domain-odd charge current. Our work uncovers distinct signatures of altermagnetism in photon drag and provides a route to all optical magnetic readouts of altermagnets.

We propose that the path to realizing the full potential of two-dimensional (2D) electronics lies in understanding and mastering their energy band tail states (BTS). Unlike silicon, which benefits from sharp band edges (Urbach energy $E_\rm U$ ~ 10 meV), today's monolayer 2D semiconductors have rough band edges ($E_\rm U$ ~ 100 meV) caused by spatial potential inhomogeneity. Comparing a physics-based electrical model to experiments, we demonstrate that BTS cause reduced effective mobility and "slow" transistor turn-on with excessive gate voltage in monolayer 2D transistors, which sets a fundamental limit for their energy-efficient operation. We also show that BTS effects in 2D transistors could be mitigated with higher gate capacitance, with strain engineering, and by using bilayer instead of monolayer 2D channels, as long as $E_\rm U$ is reduced below ~ 50 meV. This work provides a theoretical framework and design guidelines to navigate these fundamental limits, and to enable successful integration of 2D semiconductors into low-power nanoelectronics.

Polaritons and quantum vacuum dressing are usually regarded as intertwined consequences of ultrastrong light-matter coupling. Here we show that they can be controlled independently through helicity. We consider cyclotron resonance coupled to a chiral cavity supporting a single circular mode. When the helicity of the cavity field matches the cyclotron motion, energy is exchanged resonantly between light and matter, producing a large Rabi splitting and conventional polaritons, while the ground state remains the bare vacuum. Reversing the magnetic field reverses the cyclotron motion without changing the cavity. The same mode then couples through anomalous processes that create and annihilate light and matter excitations in pairs: the conventional polaritonic anticrossing disappears, while the ground state acquires squeezing and virtual excitations. These two regimes show that spectral hybridization and quantum vacuum dressing are distinct manifestations of ultrastrong coupling, and that a large Rabi splitting alone does not imply a dressed quantum vacuum. Helicity therefore provides a route to controlling polariton formation and quantum correlations as distinct resources in cavity quantum materials.

The logarithmic law of the wall is one of the most robust scaling laws of classical turbulence, yet whether it survives in a quantum fluid such as superfluid $^4$He (He II) remains unknown. At a solid wall, the viscous normal-fluid and inviscid superfluid components of He II obey fundamentally different boundary conditions, yet their motions can be coupled through quantized vortices. How these competing effects organize the near-wall flow remains an open question in quantum-fluid hydrodynamics. Here we visualize the near-wall velocity field in mechanically driven He II pipe flows at Reynolds numbers up to $1.26\times10^6$ using molecular tagging velocimetry and independently determine the wall shear stress from pressure-drop measurements. We find that the normal-fluid velocity develops a robust logarithmic profile, showing that a law-of-the-wall description persists despite the two-fluid nature of He II. Strikingly, however, the resulting wall law is distinctly nonclassical: the effective Kármán constant is less than half its classical value and remains nearly unchanged across the temperature range studied. This invariance, despite substantial changes in the relative fractions of the two components, indicates strong dynamical coupling between them. These results not only reveal how a universal law of classical turbulence is transformed by quantum hydrodynamics, but also provide valuable guidance for the design and operation of cryogenic cooling systems involving He II transport.

We develop a machine learning assisted workflow for the rapid screening of permanent magnet candidates within the CaCu$_5$ structure family. We generated more than 60,000 structures through substitutions. These compositions were screened using a combination of pretrained materials models, Materials Project data, and a machine-learning model for magnetization prediction. Four criteria, namely, metallicity, negative formation energy, energy above the convex hull $\leq 50$~meV/atom, and predicted magnetization above the adopted $\geq 0.75$~T threshold reduced the initial chemical space to 439 candidates for first-principles calculations. Density functional theory calculations revealed that 159 compounds exhibit positive axial magnetic anisotropy energy, favoring [001] over the tested in-plane directions. The resulting dataset reveals chemical trends in magnetic anisotropy across the CaCu$_5$ compositional space and provides a set of candidates for further investigation. More broadly, this work demonstrates a practical strategy for combining existing machine learning models with first-principles calculations to systematically reduce large chemical spaces to tractable sets for computationally intensive materials screening.

Ceramic materials are inorganic, predominantly nonmetallic solids whose performance is governed by the interplay among atomic bonding, crystal structure, processing, microstructure, and functional properties. Their ionic and covalent bonding provides high hardness, thermal and chemical stability, wear resistance, and diverse electrical behavior, but also limits plastic deformation and increases sensitivity to flaws, porosity, grain boundaries, and residual stresses. This review examines ceramics through the processing–microstructure–property–performance relationship, emphasizing the effects of crystal chemistry, defects, grain size, porosity, and phase stability on mechanical, thermal, electrical, and biological behavior. Conventional sintering, sol–gel processing, and additive manufacturing are discussed as key routes for controlling densification, porosity, geometry, and composition. Biomedical ceramics, including alumina, zirconia, calcium phosphates, hydroxyapatite, tricalcium phosphate, and bioactive glasses, are also reviewed. Emerging topics include nanoceramics, smart ceramics, composites, multimaterial manufacturing, defect engineering, immunomodulatory bioceramics, and sustainable processing. Major challenges remain in brittle fracture, processing heterogeneity, degradation control, scale-up, and the porosity–strength trade-off. Future advances will require integrating advanced manufacturing, multiscale characterization, predictive modeling, and data-driven design.

Several models for chirality-induced spin selectivity (CISS) in charge transfer have been proposed, but rarely compared directly with experiments. This step is essential for their validation and future progress of the field. Here we investigate a broad class of radical pair states associated with different microscopic models by computing the related electron-paramagnetic resonance spectra. This allows us to evidence peculiar signatures of different radical pair states, to study their experimental accessibility and identify conditions to verify proposed microscopic models.

In the BCS theory of superconductivity the amplitude (Higgs) mode is degenerate with the pair-breaking threshold: its frequency coincides with $2\Delta$, so it is an edge singularity rather than a true collective mode. This is why after a sudden weak perturbation at $t=0$ its oscillations decay algebraically as $1/\sqrt{t}$. We show that the retardation effects due to the phonon dynamics in the strong-coupling theory lift this degeneracy. The Higgs mode detaches from the pair-breaking edge $2\Delta_g$, set by the spectral gap, and becomes a sharp subgap excitation. We determine its frequency from the longitudinal pair susceptibility evaluated directly on the real frequency axis, using the Eilenberger equations for Migdal–Eliashberg theory with the Einstein phonon spectrum. The response of the mass renormalization supplies at least two fifths of the displacement, and possibly all of it: with it switched off, the binding falls below the resolution of the calculation. Its consequences, however, are significant because a percent-level shift transfers about a quarter of the spectral weight of the amplitude channel out of the two-quasiparticle continuum into a discrete energy level. What experiment sees is therefore not the displacement itself but its consequence: amplitude oscillations that persist instead of decaying as $1/\sqrt{t}$.

Supermoire lattices in large-angle twisted bilayers have recently been shown to emerge from periodic arrangements of commensurate stacking motifs, yet the microscopic structural mechanism governing their formation has remained unresolved. Here, we uncover the microscopic origin of supermoire order as a hierarchical lattice relaxation process. Combining force-field simulations with experimental validation via super-resolution, layer-resolved multislice electron ptychography, our results identify interlayer Se-Se repulsion at the picometer scale as the driving force, giving rise to coupled short-range (about 1 nm) moire relaxation and coexisting long-range (about 10 nm) supermoire modulation. These findings demonstrate that even picometer-scale lattice relaxation remains critical in large-angle moire systems and must be explicitly considered in understanding their emergent electronic and quantum phenomena.

Distinguishing trivial from topological superconducting phase remains a central and contested experimental challenge, since most existing probes infer the bulk phase transition indirectly, from boundary signatures that can be sensitive to local physics. Here, we propose an alternative that probes the bulk topological phase and is based on supercurrent response. We study a one-dimensional Rashba spin-orbit-coupled superconducting nanowire with an applied magnetic field that opens a topological gap. We show that for strong spin-orbit coupling, the superfluid stiffness, and consequently the supercurrent, is suppressed by a factor of two inside the topological phase, producing a non-monotonic signature of the bulk phase transition as a function of chemical potential. We further use a low-energy helical model to understand this suppression analytically. Our results show that the bulk topological phase transition can be detected through kinetic inductance measurements.

We investigate the relaxation dynamics and steady state of a qubit interacting with a coherent environment through an energy-conserving flip-flop interaction within the Markovian repeated-interaction framework. We derive an exact analytical solution for the evolving and stationary state, nonperturbative in the environmental coherence. We show that environmental coherence provides a resource for dissipative state preparation by expanding the set of accessible steady states. In particular, coherent ancillas can increase the system ground- state population beyond that of the bath, corresponding to an effective temperature below the bath temperature, and enhance its steady-state purity, with these effects controlled by the interplay between the system energy scale and the system-ancilla coupling. Nevertheless, we prove that the purity of the system can never exceed the purity of the ancilla. We further analyze the thermodynamics of the protocol and show that environmental coherence can modify and even reverse the natural direction of heat transfer, giving rise to anomalous heat flow. Remarkably, for fixed interaction parameters, the direction of the coherence-induced heat transfer is governed by the relative phase between the system and ancilla coherence, whereas their magnitudes determine the amount of heat exchanged. Our results establish environmental coherence as a resource for controlling steady-state preparation and energy transfer in repeated-interaction dynamics.

We develop a constructive framework for characterizing modulated symmetries and their gauging in $d$-dimensional lattice systems. The modulation profiles are organized as a finite-dimensional representation of the space group acting on a finite Abelian internal symmetry group. Since the corresponding automorphism group is finite, the nontrivial spatial action factors through a finite quotient of the space group, leading to periodic modulation patterns and providing a classification framework for discrete Abelian modulated symmetries. The symmetry-allowed local interactions are systematically obtained from a kernel construction, which also yields an algebra of open operators. Upon gauging, its elements are transmuted into extended Wilson and boundary operators while retaining their algebraic relations. In the deconfined regime, the resulting algebra realizes a mixed 't Hooft anomaly, providing a microscopic route to Abelian crystalline symmetry-enriched topological phases (SETs). These SETs do not mix electric and magnetic sectors, which transform in mutually contragredient representations, thereby preserving their braiding pairing. We illustrate the framework through explicit examples and show that several models present in the literature fit naturally within our construction.

In ultraclean conductors, electron-electron collisions can make transport hydrodynamic. In a Berry-curved band, these collisions can also produce two-particle coordinate shifts, which contribute to the anomalous Hall current in the presence of a transport electric field. We develop a kinetic theory of this contribution for a two-dimensional massive Dirac Fermi liquid with weak contact interactions and weak short-range disorder. The computed response is independent of interaction strength at leading Born order. Its contribution to the anomalous Hall conductivity is comparable to the thermal correction to the intrinsic anomalous Hall conductivity. The existence of the momentum zero mode of the electron-electron collision integral leads to a nontrivial frequency dependence of the anomalous Hall response considered in this work. In particular, the limits of vanishing frequency (dc) and vanishing disorder do not commute. In the dc limit, the momentum response to the transport field grows inversely with the momentum relaxation rate. This allows arbitrarily weak, energy-dependent impurity scattering to produce a finite correction by coupling conserved momentum to the modes relaxed by electron-electron scattering. This correction disappears when the clean limit is taken before the zero-frequency limit. As a result, the interaction-induced Hall response retains information about the mechanism of momentum relaxation even as the overall disorder strength tends to zero.

Confined epitaxy has recently emerged as a novel methodology for controlled growth of high-quality monolayer two-dimensional (2D) materials. However, mechanistic understanding remains limited to analysing nucleus adsorption and diffusion barriers. Here, I discover that van der Waals (vdW) confinement not only affects the specific adsorption and diffusion of nuclei on confined substrates but also induces strong coupling to atomic forces at the interface. Using artificial intelligence (AI) assisted density functional theory (DFT) calculations, I study how vdW confinement couples to the atomic motion of monolayer NbSe2 grown between c-plane sapphire and hexagonal boron nitride (h-BN). The calculated force-electronic landscape yields large mechanical forces of +0.070 and -0.04 eV per Angstrom on Nb and Se, respectively, giving rise to a unit-cell interfacial interaction energy up to 2.4 eV, comparable to reported adsorption and diffusion energies on similar substrates. The results indicate that interfacial mechanics may explain the success of confined epitaxy. The findings suggest that tuning interfacial mechanics, and related vdW mechanochemistry, could be a promising route to high-throughput, high-quality materials synthesis.

A long-term goal of quantum simulation is to faithfully reproduce the low-energy Hamiltonians of correlated quantum materials, establishing a direct connection between solid-state experiment, electronic-structure theory, and programmable many-body systems. Here, we introduce an integrated quantum-simulation architecture based on fermionic alkaline-earth atoms that enables programmable control over the key ingredients of multi-orbital material Hamiltonians. Long-lived clock states encode synthetic orbitals, their differential polarizabilities generate orbital-selective tunneling, and contact interactions provide multi-orbital Hubbard and Hund couplings. Spatially structured coherent driving on the ultra-narrow clock transition further realizes symmetry-selective inter-orbital hybridization, while the clock detuning independently controls orbital energy offsets. In this way, the spatial symmetries of solid-state orbitals can be encoded directly into the effective Hamiltonian, even though the atoms themselves remain in conventional $s$-wave Wannier orbitals of the lowest optical-lattice bands. We demonstrate the resulting integrated control using the four-band low-energy Hamiltonian of the bilayer nickelate La$_3$Ni$_2$O$_7$ as a demanding benchmark. Self-consistent calculations show that the microscopic parameters obtained from first-principles modeling can be reproduced within a single experimentally accessible lattice configuration and independently programmed over substantial parameter ranges. Our results establish a general route for translating material-derived multi-orbital Hamiltonians into programmable ultracold-atom quantum simulators.

Recent scanning tunneling microscopy has directly imaged electronic crystals in rhombohedral hexalayer graphene, and magnetotransport measurements suggest that superconductivity and charge-density-wave order emerge from a common spin-valley-polarized ferromagnetic metal at nearby carrier densities. Motivated by these observations, we ask whether collective modes in a magnetic Wigner crystal can mediate pairing in this setting. We address this question by studying the Cooper problem for two electrons in the first conduction band of the Wigner crystal. Unlike conventional phonon-mediated pairing, the collective mode (boson) energies and single-particle (fermion) dispersion are comparable scales controlled by the electron density, leaving no small parameter for an adiabatic expansion. Moreover, because the magnetic Wigner crystal is not time-reversal invariant, the usual Cooper logarithmic divergence in the pairing susceptibility is absent, so the attraction must exceed a finite threshold for pairing to occur. These unusual features motivate a numerical experiment to see whether the crystal's own vibrations can bind electrons. We obtain the crystalline ground state and its collective mode spectrum within Hartree–Fock and time-dependent Hartree–Fock approximation, and derive the electron–phonon Hamiltonian using the quasiboson approximation. Solving the resulting two-electron problem, we find that phonon-mediated attraction exceeds the pairing threshold, with chiral $p$-wave pairing as the leading instability. Within these approximations, we show that collective modes of a Wigner crystal can indeed favor chiral pairing despite broken time-reversal symmetry. Our results provide an encouraging starting point for developing a full many-body theory to study electronic crystallization and superconductivity.