Papers

Detector cost remains a barrier to the widespread adoption of mid-wave infrared (3-5 micron) technology. PbSe, an inexpensive narrow band gap IV-VI semiconductor that has been used since the early 1940s, delivers high performance for infrared detection despite the abundance of grain boundaries in polycrystalline films. Epitaxial growth, however, could provide superior crystalline quality and interfaces, but suitable substrates remain limited for PbSe. Recent PbSe heteroepitaxy has focused primarily on III-V, II-VI and group-IV substrates that each offer a comparatively narrow range of lattice-matched alloys for heterostructure engineering. Here we show that InP-based heteroepitaxy provides access to a broader materials platform while limiting the lattice mismatch with PbSe to approximately 4%. We grow 150-nm thick PbSe films by molecular beam epitaxy on 200-nm thick In0.53Ga0.47As and In0.52Al0.48As buffers on (001) InP substrates. Reflection high-energy electron diffraction and X-ray diffraction show (001)-oriented rock-salt PbSe with an out-of-plane lattice constant of 6.12 Angstrom on both buffers. Photoluminescence (PL) is observed from room-temperature down to 12 K and the peak wavelength red-shifts from 3.7 to 5.0 microns. Under identical measurement conditions, the room-temperature peak PL intensities from films on In0.53Ga0.47As and In0.52Al0.48As are approximately 1.9x and 1.3x that of a PbSe on GaAs substrate reference, respectively. These results establish an InP-compatible platform for integrating narrow band-gap PbSe with a broad range of ternary and quaternary III-V alloys, including, for example, structures in which In0.53Ga0.47As serves as both a short-wave infrared absorber and a template for PbSe growth.

Two-dimensional metal-organic frameworks (2D MOFs), with diverse topological architectures, provide a powerful platform for exploring unconventional electronic and lattice-dynamical responses. Yet their structural diversity remains fundamentally constrained by the fixed geometry of high-symmetry ligands. Here, we introduce an encoded asymmetric ligand, benzo[b]triphenylene-2,3,6,7,11,12-hexaol (BTH), for metal-selective topological assembly. By integrating multi-site coordination fields with sterically differentiated environments, BTH exhibits distinct topological programmability: different divalent metal ions direct divergent framework architectures. Specifically, coordination of BTH with divalent Cu(II) and Zn(II) ions assembles Cu-BTH-MOF with a dual-mode hexagonal pore topology and Zn-BTH-MOF with uniform hexagonal channels, respectively, as supported by PXRD Pawley refinement, structural simulations, and pore-size distribution analysis. Furthermore, this topological divergence is accompanied by a significant divergence in charge-transport properties, with Cu-BTH-MOF reaching an electrical conductivity of 1.186 x 10-3 S cm-1, more than six orders of magnitude higher than that of Zn-BTH-MOF (3.38 x 10-10 S cm-1). This work establishes ligand desymmetrization as a programmable strategy for metal-selective topological diversification in 2D MOFs.

Although minimalist models for patchy attractive particles have revealed powerful design rules for how particle valence directs colloidal assembly, less work has focused on comparably simple models of reversible, network-forming star polymers. Here, we use relative-entropy coarse-graining and simulation results from finer-resolution bead–spring star polymers to generate 5-bead models of dynamic, end-associating four-armed poly(ethylene glycol) macromers. Our results comparing structural correlations, network connectivity, and phase behavior of the coarse- and fine-grained models provide insight into how the accuracy and transferability of the coarse-grained models depend on the state point chosen for coarse-graining. The results also reveal intrinsic trade-offs between reducing degrees of freedom and expanding the range of effective interactions in coarse-graining that impact the total number of pairwise interactions in the resulting model, with implications for its computational efficiency.

Spatiotemporal fluctuations across multiple scales govern and characterize the emergent properties, phase boundaries, and low-energy excitations of strongly correlated matter. However, capturing these dynamics has remained a major experimental challenge, as conventional probes typically offer either high spatial or temporal resolution, but not both simultaneously. Here, we leverage high-fidelity wide-field imaging of dense diamond nitrogen vacancy center ensembles to measure the momentum and frequency power spectral density of magnetic fluctuations. To access spatial wavevectors below the diffraction limit, we tune the sensing volume continuously through optical depletion. This approach enables study of equilibrium and driven fluctuations across three orders of magnitude in spatial scale and tunable frequency bands, providing a direct means to map low-energy, long-wavelength fluctuations in correlated systems.

Hybrid organic-inorganic perovskite heterostructures are emerging platforms for energy conversion and optoelectronic devices, yet the effects of composition and surface terminations on band alignment remain poorly understood. Here, using high-throughput first-principles calculations, we systematically reveal the effect of composition and surface termination on the band alignment of 820 heterostructures formed between poly(3-hexylthiophene) (P3HT) variants and conventional and mixed-cation metal halide perovskites. Band edge analysis predicts concentration dependent band alignments, with most Pb and Sn based perovskites exhibiting Type II and III behavior while mixed-cation CsMASnBr3 uniquely forms Type-I junctions with all P3HT variants. Explicit interface calculations reveal that surface termination can reverse the predicted alignment in conventional tin perovskites, while the mixed cation perovskite preserves Type-I alignment with P3HT regardless of termination. Despite negligible charge transfer, termination dependent band offsets produce markedly different carrier confinement, establishing design principles for engineering P3HT/perovskite interfaces.

We present a transferable graph neural network (GNN) surrogate framework for molecular dynamics (MD) that directly predicts atomic displacements and propagates atomistic configurations without explicit force evaluation or numerical time integration. The central objective of this work is to establish whether a common GNN formulation can represent atomic dynamics across materials with fundamentally different crystal symmetries and coordination environments. The same network architecture, feature representation, graph construction, and training protocol are applied without symmetry-specific modification to face-centered cubic (FCC) aluminum, body-centered cubic (BCC) iron, and hexagonal close-packed (HCP) magnesium. Across these distinct elemental and crystallographic systems, the framework achieves position-prediction errors on the order of 10^-4 Angstrom^2 and supports stable autoregressive propagation to nanosecond time scales. The predicted trajectories preserve thermodynamic stability, characteristic coordination-shell structure in the radial distribution functions, and temperature-dependent mean-squared-displacement behavior. In particular, the framework captures the closely spaced coordination shells of BCC iron and the anisotropic coordination environment of HCP magnesium without introducing lattice-specific representations. These results demonstrate that direct GNN-based atomic propagation can be formulated as a transferable framework across different elements, lattice symmetries, and coordination geometries, providing a pathway toward generalizable surrogate models for accelerated molecular dynamics.

The symmetry-protected multiple Majorana zero modes (MZMs) can be manipulated under external fields and have emerged as a promising pathway toward realizing topological quantum computing. While the suitable materials hosting multiple MZMs are still scarce, we propose a feasible candidate platform named superconducting topological crystalline metals (STCMs) that simultaneously possess symmetry-protected topological bands and intrinsic superconductivity. Model analyses demonstrate that the interplay among s-wave superconductivity, mirror symmetry-protected multiple surface Dirac cones, and the introduced spin splitting leads to high BdG Chern numbers of $\mathcal{N} = \pm C_M$, where $C_M$ is mirror Chern number of the STCM. First-principles calculations identify the experimentally synthesized superconductor ZrRuAs as a promising candidate with $C_M=2$, hosting two symmetry-protected surface Dirac cones. When integrated into a heterostructure with the ferromagnetic insulator (FMI) such as GdI$_{2}$, a topological superconducting phase with $\mathcal{N} = -2$ can be realized, giving rise to two branches of MZMs. This new scheme offers advantages of structural simplicity and tunability, making the FMI/STCM heterostructure an ideal platform for investigating multipole MZMs and novel topological qubit.

Generative models now propose millions of "stable" crystal structures, and their own referees have shown that stability is not discovery; no public benchmark asks whether a candidate has the physics to do a job. For superconductors the job is twofold: to pair, with a definite gap symmetry, and to become wire. We present a physics judge that answers both from a structure alone (DFT+U, a gated Wannier model, the full rank-4 RPA susceptibility on a $24^3$ mesh, the linearized gap equation, an irreducible-representation classifier, a manufacturability funnel) and measure what it says about what generators propose. With answer keys pre-registered before computing, the judge was calibrated on six known superconductors (Nb, Nb$_3$Sn, MgB$_2$, BaFe$_2$As$_2$, La$_{2-x}$Sr$_x$CuO$_4$, YBa$_2$Cu$_3$O$_7$), recovering the expected class in all six after two dated corrections. On the ruthenium analogue of the iron pnictide, with two runs and their criterion pre-registered the day before, it returns a null verdict at the same physical interaction where iron gives s$\pm$ ($\lambda_1 \le 0.0007$ versus 0.096; critical U 4.17 versus 0.97 eV); the pre-registered equal-alpha run fails the letter of the criterion, and we declare the resolution in favour of absolute U as post-hoc. The funnel reproduces the industrial map with thresholds fixed before running. Three generation audits follow: a descriptor sweep over 150 Materials Project metals re-finds the canon; 1,248 MatterGen structures yield 0 candidates that are new, stable and carry a pairing motif; mechanism filters over 47,893 compounds, validated by a blind hold-out, re-derive the community's analogies: geometry plus d-count is necessary but not sufficient. Generation re-finds what is known; judgment is the bottleneck. We propose a public benchmark over the eleven lists of AI-proposed superconductor candidates, none of which classifies gap symmetry.

Light-driven control of material symmetry enables the engineering of phenomena forbidden in equilibrium. Although electromagnetic fields have been used to break time-reversal symmetry, its dynamic control on ultrafast timescales in nonmagnetic insulating oxides remains virtually unexplored. Here, we demonstrate simultaneous magnetic symmetry lowering and timereversal-symmetry breaking in cubic SrTiO3 driven by an off-resonant, elliptically polarized THz pulse. Second harmonic generation (SHG) polarimetry reveals emergent SHG circular dichroism inconsistent with third-order nonlinear processes under cubic m3m symmetry. The SHG polar patterns exhibit mirror-symmetry breaking, indicating a transient reduction to tetragonal 4/mm'm' magnetic symmetry. Furthermore, the SHG response scales linearly with the angular momentum of THz pulse, providing direct evidence for THz-field-induced timereversal-symmetry breaking. These results establish a direct pathway for ultrafast symmetry control in non-magnetic oxides, enabling dynamic manipulation of emergent phases on ultrafast timescales.

We systematically investigated the phase stability and pressure dependence of the elastic properties of four GeO2 polymorphs: rutile-, CaCl2-, alpha-PbO2-, and pyrite-type phases using theoretical calculations based on density functional theory. The elastic constants were calculated at 5 GPa intervals within the respective stability ranges of the four phases, as determined from static enthalpy calculations. We further employed a classical strain-coupled Landau free-energy expansion to describe the pressure evolution of the elastic response associated with the rutile- to CaCl2-type transition and to elucidate the origin of the elastic softening near the transition. The rutile- to CaCl2-type phase transition is consistent with a Landau-type second-order transition, with a critical pressure of 14.6 GPa obtained from the strain-based analysis. As the transition pressure approaches, elastic softening develops in the rutile-type phase, resulting in anomalous pressure dependence of the bulk and shear modulus. The calculated elastic-wave anisotropy increases markedly near the transition, primarily due to the rapid reduction in shear-wave velocity, reaching a maximum of approximately 122% at 22.5 GPa. Following the transition, the anisotropy decreases sharply in the CaCl2-type phase and exhibits a discontinuity at the CaCl2-type/alpha-PbO2 -type phase boundary. The higher-pressure alpha-PbO2- and pyrite-type phases exhibit comparatively weak pressure dependence of anisotropy, with a small discontinuity at their respective phase transition boundaries. The pyrite-type phase has the lowest anisotropy, reaching only approximately 4-5% at high pressure, consistent with the high-symmetry cubic structure and nearly isotropic elastic-wave propagation.

Lutetium hydrides (LuH$_x$, $1.75 \leq x \leq 3$) form a diverse series of phases, several of which superconduct under pressure. Characterizing their electronic properties has remained challenging owing to a high propensity for hydrogen defect formation, and recent angle-resolved photoemission (ARPES) measurements reveal puzzling flat-band regions that position these materials as candidates where superconductivity and flat-band physics may intersect. Here, by combining density functional theory, dynamical mean-field theory, and the constrained random-phase approximation, we uncover the microscopic origin and correlation nature of these flat bands. Across all compositions, the screened on-site Coulomb interaction is larger for H-s states than for Lu-$d$ states due to compact hydrogen orbitals. Nevertheless, these systems remain weakly correlated metals: the nearly filled H-$s$ shell admits little charge fluctuation, so its large interaction acts as a static level shift rather than a source of correlation. Although hydrogen primarily occupies tetrahedral sites at $x=2$, we discover that anti-site defects–where hydrogens occupy slightly unfavorable octahedral sites–generate both the ARPES flat-band features and the low-energy optical absorption peak, attesting to the usual defective nature of such materials in experimental samples. We further find that correlation strength is governed primarily by hydrogen orbital filling at these sites rather than the interaction magnitude itself. Consequently, we identify hydrogen orbital filling as the fundamental organizing principle dictating correlation and low-energy flat-band physics in lutetium hydrides.

Dissimilar Al/Cu joints are essential to battery-pack assemblies; however, their mechanical strength is limited by brittle Al-Cu intermetallic compounds (IMCs) such as Al2Cu and Al4Cu9. Interlayer strategies to suppress these phases remain largely empirical, lacking a predictive framework linking interlayer chemistry to the phases that form and to their intrinsic mechanical character. Here an Ag interlayer is introduced and combines computational thermodynamics, first-principles calculations, microstructural characterization, and mechanical testing into a single self-consistent description of the joint. CALculation of PHAse Diagrams (CALPHAD) equilibrium and Scheil simulations predict the solidification path of the Al-rich Al-Ag fusion zone and explain why Cu incorporation is limited when Ag is present; energy-dispersive X-ray spectroscopy (EDS) and electron backscatter diffraction (EBSD) confirm an FCC Al-Ag solid solution as the dominant constituent. First-principles phonon calculations within the quasiharmonic approximation yield finite-temperature entropy and Gibbs energy, benchmarked against CALPHAD, while elastic constants assess ductility via the Pugh criterion (i.e., the bulk/shear (B/G) modulus ratio). All Al-Ag phases, including the observed solid solution, exceed the Pugh threshold of 1.75, whereas the targeted Al-Cu IMCs do not, giving a mechanistic basis for the interlayer's effectiveness. This microstructural change translates into improved performance: nominal strength rises from 47.9 to 67.4 MPa. Nanoindentation gives a fusion-zone reduced modulus of 82.8 GPa (Young's modulus 82.0 GPa), versus a calculated 0 K Voigt-Reuss-Hill value of 71.4 GPa. The present work establishes a transferable CALPHAD, first-principles, and experiment workflow for rational interlayer selection in dissimilar-metal joining.

The valence electron concentration (VEC) is the most widely used predictor of FCC against BCC stability in high-entropy alloys (HEAs), yet it is a compositional average carrying no information about atomic size. Using the macroscopic atom model, we show that the mixing enthalpy is almost size-blind, shifting by less than 6% even when constituent volumes differ by a factor of 2, so that size can act only on the electron count. That action equals exactly the covariance of the atomic surface $V^{2/3}$ with the valence electron count, divided by its mean. This covariance is not free. Volume and valence are strongly anti-correlated across the elements used to build HEAs, so the size-corrected count is an affine rescaling of VEC over 265 characterized alloys and improves no prediction. VEC already encodes atomic size, which explains its success and locates its failure among large, electron-rich elements. Chemistry sets the enthalpy through one switch element.

The energetic effect of a force error depends on atomic motion. We establish a directional residual-work coefficient combining directional curvature mismatch with the spatial distribution of the residual response. For conservative potentials force-matched at an anchor, it determines the leading signed work at the first crossing of a small force-error budget. At a 474-atom lithium-electrolyte interface, predictions fixed before future reference evaluations differ from measurements by less than 4.6% of predicted work across 24 prescribed endpoints. Changing only the initial velocity direction at fixed structure and initial total kinetic energy reverses the force-work ranking. At the same admitted time of 0.25 fs, one direction gives an 11.6% larger maximum force residual but 36.1% less work. The reversal recurs at a second structure. The framework connects force tolerances to reference-energy transfer, providing a physical basis for potential assessment and adaptive reference allocation.

We generalize the sample-based Krylov quantum diagonalization (SKQD) method from ground-state calculations to the evaluation of single-particle Green's functions. By constructing and sampling unitary Krylov subspaces in the N +/- 1 particle-number sectors and evaluating all sector-connecting overlaps classically, the approach reconstructs the Green's function via a Lanczos continued fraction while retaining the shallow-circuit, ancilla-free character of SKQD. The quantum device is required only to prepare and sample short-time evolutions. Applied to the particle-hole-symmetric single-impurity Anderson model in chain geometry, with the discrete bath representation used in dynamical mean-field theory (DMFT), the method recovers the spectral function using a relatively small fraction of the full Hilbert space. Across a range of interaction strengths that spans the metal-insulator transition, the main spectral features are reproduced. These results suggest that SKQD-based Green's-function calculations may allow DMFT impurity solvers with a larger number of bath sites on near-term quantum hardware than is currently practical.

The effects of disorder on topological phases of matter are typically either preservation of topology or its destruction. For example, the quantum Hall effect's quantization and chiral edge mode remain robust until a strong-disorder percolation transition exits the topological phase. Disorder can also enlarge a preexisting topological phase, yielding a topological Anderson insulator (TAI). However, the reliance of TAI and other theoretical treatments on perturbatively averaging out long-wavelength randomness suggests that additional effects might appear when the disorder involves localized defects. Here we show that a finite density of randomly distributed defects can generate various new topological phase transitions. This route to disorder-induced topology can be viewed as the formation of topological impurity bands (TIB) and is applicable even if the initial clean model is a trivial band insulator. The theory relies on an orbital-dependent vorticity of impurity bound states, which we derive analytically near a generic Dirac cone phase transition as well as using the Chern insulator lattice models of Qi-Wu-Zhang and Haldane. Their numerically computed phase diagrams at 3% defect density show robust topological transitions in distinct TIB and TAI regimes, suggesting a local route to topological phases.

Two-dimensional massless Dirac systems, exemplified by graphene, are known to exhibit a divergent orbital diamagnetic susceptibility that scales linearly with system size. Motivated by viewing a chiral edge state as one half of an enlarged analogue of a benzene ring, we study Chern insulators under open boundary conditions and find the same divergent scaling. This giant diamagnetism is robust against disorder, revealing its topological nature. Our results further suggest a profound connection to the divergent diamagnetism of massless Dirac systems.

Conventional semi-local density functional approximations for the exchange-correlation energy systematically underestimate fundamental band gaps. Advanced meta-generalized gradient approximations (meta-GGAs) can partially overcome this limitation through their orbital dependence via the kinetic energy density. In principle, the flexible meta-GGA form should allow for balanced performance across diverse properties. However, atomization energies, reaction barrier heights, and lattice constants, as well as band gaps, exhibit different sensitivities to the large parameter space of meta-GGA functionals. In this work, we explore the space of appropriate norms that guide the r$^2$SCAN-type functional construction through the interpolation function connecting two fundamental paradigms: the one-electron limit and the uniform electron gas limit. We introduce local modifications to a strongly-smoothed interpolation function and investigate their impact on functional performance. To further probe the limits of the meta-GGA framework, we include spin-unpolarized bonded systems among the set of norms. The resulting bonded-norm bn-r$^2$SCAN meta-GGA achieves balance: band-gap predictions approaching the accuracy of the ultra-nonlocal LAK meta-GGA and lattice constants of nearly r$^2$SCAN accuracy.

Layer compensation can conceal spin polarization behind a spin-degenerate bulk spectrum in antialtermagnets, preventing spectroscopic identification of the underlying magnetic order. Here we show that the orbital effect of an in-plane magnetic field converts the hidden spin texture into an observable spin splitting with momentum parity opposite to that of the underlying exchange order, thereby restoring spectroscopic access. Once the parity is determined, complementary response functions in the weak-field regime further resolve its wave character. Within a minimal model, we illustrate that a sum rule over the difference of spectral functions between opposite spins isolates the momentum gradient of the form factor and differentiates hidden even-parity orders, whereas for odd-parity sectors the induced net spin polarization exhibits characteristic field-amplitude and angular dependences. These results establish orbital-field-induced spin splitting as a generic route to identifying the hidden altermagnetic order parameter without layer resolution.

We prove that, for any given sufficiently regular one-particle density, there exists a unique external potential for which the solution to the many-body Schrödinger equation has this prescribed density. This implies in particular that one can exactly reproduce the time-dependent density of an interacting system using non-interacting electrons, which is at the heart of time-dependent density functional theory. Our result covers the Coulomb interaction and densities arising from extended nuclei.

We provide the first fully rigorous justification of time-dependent density functional theory in the continuum: Given a time-dependent density, we prove that there exists an external potential, unique up to a time-dependent constant, such that the corresponding Schrödinger equation reproduces the given density. This potential can be obtained with an iteration scheme. Our argument covers Coulomb interactions and does not need any Taylor expansion in time. It instead requires analyticity in space for the density and potential, which is compatible with extended nuclei.

We report a neutron diffraction study of the structural and magnetic properties of a family of ferro- and ferrimagnetic Prussian blue analogues (PBAs), $A_4$[Fe(CN)$_6$]$_{2.7}$ ($A$ = Co, Mn, Ni), Rb$_2$Ni$_4$[Fe(CN)$_6$]$_{3.3}$, and Mn$_4$[Cr(CN)$_6$]$_{2.7}$, as a function of temperature (2–450~K) and applied magnetic field. All bimetallic compounds of the Fm$\overline{3}$m family exhibit a broad diffuse feature at low scattering angle, which we identify, through comparison with the cation-stabilized Rb$_2$NiFe framework, as an intrinsic signature of correlated vacancies and their associated interstitial water. High-temperature diffraction reveals a continuous crossover from positive to negative thermal expansion in CoFe and MnFe upon dehydration, while NiFe remains structurally robust up to 450~K. At low temperature, all compounds order in a collinear ferrimagnetic state with propagation vector $\mathbf{k}=(0,0,0)$, except MnFe, which adopts a partially frustrated magnetic structure with $\mathbf{k}=(1,0,0)$. A moderate magnetic field of $B_c = 1.3$~T drives a spin reorientation in MnFe toward the collinear $\mathbf{k}=(0,0,0)$ ferrimagnetic state common to the other compounds; the same transition is independently induced by dehydration. A minimal Heisenberg model shows that this transition results from a near-compensation between antiferromagnetic Mn–Fe coupling and a geometrically frustrated antiferromagnetic Mn–Mn interaction on the face-centered-cubic Mn sublattice, placing MnFe in the vicinity of a magnetic compensation point. These results resolve a longstanding ambiguity in the interpretation of the Fe $K$-edge XMCD response of MnFe-based PBAs, and establish water content as a key parameter controlling both the structural and magnetic stability of this family of materials, with direct relevance to their use as battery electrodes.

Despite the pivotal role of twist in modulating physical properties at van der Waals (vdW) interfaces, the mechanics governing torsional response remain poorly understood. Here, we probe twist mechanics at homo- and heterogeneous vdW interfaces, together with their sliding behaviors within a unified experimental framework. For both systems, the peak torque scales nearly linearly with contact area, in contrast to predictions from linear elastic and rigid models. Remarkably, while the sliding friction of the two interfaces diverges by over three orders of magnitude owing to different scaling laws, the corresponding torque follows the same linear scaling and differs by only about twenty-fold. Large-scale atomistic simulations reveal an edge-dominated yielding mechanism for torsional motion, wherein elastic reconstruction shifts the effective load-bearing region toward the edges, eliminating torque from the contact interior. This mechanism contrasts with the bulk-mediated stress transmission governing translational sliding, a distinction rooted in the different loading geometries inherent to the two motion modes, where torsional loading necessitates perimeter actuation, whereas sliding enables center-driven loading. This symmetry-imposed divergence demonstrates that translational and torsional properties cannot be predicted from one another at vdW interfaces, providing critical insights for the design of dynamically reconfigurable micro- and nanoelectromechanical devices.

Molar heat capacity at constant pressure, C_p (T), is a central thermodynamic quantity in materials science, but it remains difficult to calculate accurately from first principles when anharmonic vibrational effects become important. In this work, rocksalt ZrC is used as a high-temperature benchmark for the Beyond Quasi-Harmonic (BQH) method, a prepared-supercell first-principles approach that extracts anharmonic vibrational energy directly from density-functional-theory energy evaluations. The calculated BQH molar heat capacity is compared with CALPHAD reference values, a fully anharmonic thermodynamic-integration calculation, a calculated C_v (T) curve from the present work, and a quasi-harmonic calculation. The BQH curve gives a substantial improvement beyond C_v (T) and beyond the quasi-harmonic approximation. Because ZrC is electronically conductive, an electronic heat-capacity correction was also estimated from the density of states at the Fermi level and added to the vibrational BQH result. This correction brings the calculated molar heat capacity into close agreement with the fully anharmonic theoretical benchmark through approximately 1200 K. These results show that the BQH method fully captures important anharmonic phonon contributions missing from ordinary quasi-harmonic calculations.

Quasi-static sensing, i.e., measurement of a sensor signal change induced by analyte presence with respect to a baseline signal observed in a reference gas beforehand, is the state of the art for qualitative and quantitative analyte identification in chemiresistive sensing. However, this approach is prone to baseline drift and, especially for inexpensive miniaturized point-of-care sensors, repeated calibration with reference gas is not feasible. To access reliable baseline information, active switching between analyte and reference gas would be required, causing a limitation for miniaturized implementation. Dynamic excitation of sensors offers an alternative: Via external stimuli the sensor is reversibly driven out of equilibrium in a controlled way, and the resulting transient sensor response, which is dependent on analytes present, is recorded and interpreted. Correlation of excitation and response signals can reduce effects of baseline drift and furthermore, dynamic features in sensor responses may contain valuable information. Especially light activation is a powerful and potentially miniaturizable approach to agitate sorption processes and therefore induce dynamics. In this work we report photothermal heating of hybrid, chemiresistive gold nanoparticle composites via LED excitation matching the plasmon resonance, to dynamically shift the analyte sorption equilibrium and induce dynamic sensor responses in a highly controlled way. We demonstrate that these sensor responses enable the detection of volatile organic compounds (VOC) via interpretation of differential signal components and that this approach improves the chemiresistors' baseline stability.

Hydrogen isotope retention in plasma facing and structural alloys is a central materials challenge for deuterium-tritium fusion. Motivated by ion beam irradiation experiments and first principles calculations, we identify an irradiation-enabled mechanism whereby solute segregation to defect sinks enhances hydrogen isotope trapping. Triple-ion irradiation of reduced activation ferritic-martensitic steel F82H reveals pronounced segregation of Cr and Ta to cavity surfaces. Density functional theory shows that these segregants markedly increase H stability at cavities by strengthening binding energies and increasing migration barriers, leading to substantially higher attention. The effect originates from solute-tuned electronic structure: Ta promotes strong H 1s-metal d orbital hybridization, whereas Cr shifts the surface d-band toward a more favorable bonding configuration. These findings provide an atomistic link between irradiation-induced segregation and elevated-temperature hydrogen isotope retention and alloy chemistry routes to control tritium inventory in fusion environments.

Valley splitting sets the energy scale at which spin and valley degrees of freedom hybridize in silicon quantum-well qubits, but its sensitivity to interface structure makes it difficult to predict. Using the valleyor basis, we formulate a two-band effective-mass model for intervalley coupling in a finite quantum well and develop an analytical framework for treating non-perturbative effects of shear strain and wiggle-well potentials. For a $z$-independent coupling $V_s\tau_2$, corresponding to uniform shear strain, we construct a variational state from the exact plane-wave valleyors and a hard-wall envelope. This yields closed-form expressions for the two lowest states and their splitting, including the characteristic oscillatory $|\sin(k_{\rm min}L)|$ dependence. The variational result agrees with exact diagonalization to within $\sim1\%$ for realistic couplings, and provides a simple prescription for tuning the shear strain away from the nodes to enhance the valley splitting. We further show that finite barrier heights primarily renormalize the effective width of the quantum well while preserving the oscillatory dependence. For a wiggle-well coupling $V_w\cos(k_wz)\tau_1$, the valleyor representation reveals a crossover near the $k_w=2k_1$ resonance from wiggle-dominated splitting to orbital quantization. Remarkably, at high wiggle-well amplitudes, the empty-box energy scale predominantly dictates the near-resonant valley splitting, while the wiggle-well potential enters only as a sub-leading correction. This behavior can be viewed as asymptotic freedom for spin qubits. Away from resonance, the splitting exhibits a broadly peaked resonance with diffraction-like side-lobes as a function of detuning.

Within the rapidly growing family of two-dimensional (2D) materials, 2D ferromagnetic (FM) materials have attracted a great deal of recent attention. The ferromagnetism in 2D FM materials originates from the underlying exchange interactions. In particular, metal-insulator transitions (MITs) in 2D FM materials induced via various modulation strategies is critical to the design of 2D electronic devices with reduced sizes (e.g. transistor). However, the critical behaviors of exchange interactions and their effects on the Curie temperatures near MITs remains to be clarified. By taking the 2D FM 1T-FeX2 (X=Cl, Br, I) monolayers as the testbeds, we computationally study the critical behaviors of the exchange interactions in the vicinity of the MITs driven by the on-site Coulomb electron-electon interactions. The FM superexchange interactions and the direct exchange interactions are found to energetically favor the halfmetallic and semiconducting states, respectively. In addition, the halfmetallic states have the stronger FM couplings and thus the higher Curie temperatures. This study provides a comprehensive understanding of the interrelations between MITs and exchange interactions and could be useful for the device design requiring both MITs and exchange-interaction related magnetic properties, particularly robust magnetic ordering and higher Curie temperatures, in 2D FM materials.

Artificial kagome lattices provide a route to electronic flat bands, geometric frustration, and correlation driven phases, but their realization in atomically controlled two-dimensional materials remains scarce. Here, we show that commensurate twisted bilayer germanene on Ge2Pt produces two electronically distinct large-angle moiré phases. Scanning tunneling microscopy measurements and density functional theory calculations reveal that commensurate twisted bilayers that are odd under an exchange of sublattices are semiconducting, whereas the twisted bilayers with an even parity are metallic. The twisted bilayers with an even parity host an empty state resonance that exhibits an emergent decorated kagome structure with a C3 symmetry. These results establish large-angle twisted germanene as a platform for engineering kagome-like electronic states in a buckled two-dimensional material.

Metal phthalocyanines (MPc) are a versatile molecular platform for applications ranging from organic optoelectronic devices to single-atom catalysis (SAC). Their adsorption and layer formation on the prototypical transparent electrode substrates of organic optoelectronic devices is directly relevant for charge injection and transport across the organic-oxide interface. Moreover, the well-defined M-N$_4$ coordination of the metal cation defines their activity as SACs for (electro-)catalysis. Here, the adsorption of the metal-free phthalocyanine (H$_2$Pc) is characterized on In$_2$O$_3$(111) using low-temperature STM, nc-AFM, and STS. In$_2$O$_3$ is not only a model system of indium tin oxide (ITO) but also an active catalytic material for CO$_2$ reduction. H$_2$Pc adsorbs in the same site and configuration reported for copper phthalocyanine [J. Mater. Chem. C 13, 17650-17661 (2025)] and for the majority of cobalt phthalocyanine [Surf. Sci. 722, 122065 (2022)]. Despite this shared preference in adsorption site, H$_2$Pc cannot be organized into extended and ordered monolayer structures by gentle annealing: the molecule starts to decompose at $\approx$50$^\circ$C, well below the temperature used to grow monolayers of CoPc and CuPc. Self-metalation is not observed on stoichiometric In$_2$O$_3$(111). On the reduced surface where In$^0$ adatoms are present, new H$_2$Pc-related features appear but cannot be identified by imaging only. The comparison of H$_2$Pc with CoPc and CuPc identifies distinct roles of the central metal ion in the metal-Pc/In$_2$O$_3$(111) systems: it acts as a structural anchor that stabilizes the macrocycle against decomposition on the surface, and it modifies the frontier-orbital character in ways that determine whether a second adsorption configuration is populated.