Materials Science · Cross-listed from cs.AI
CP-Agent: A Harness-Engineered Agent for Crystal Plasticity Simulation Workflows
Samuel Onimpa Alfred, Abhishek Kumar and Veera Sundararaghavan
Crystal plasticity (CP) simulations predict the mechanical behavior of polycrystalline metals, yet their routine use is hindered by the manual effort of configuring heterogeneous tools, orchestrating multi-step data pipelines, and calibrating constitutive parameters against experiments. These bottlenecks impede productivity in systematic parameter studies, motivating interest in automated workflows. This study presents CP-
Agent, a harness-engineered LLM-based
agent that autonomously executes complete CP modeling workflows from natural-
language tasks. Operating under the ReAct paradigm, the
agent reasons about tool selection and sequencing while delegating numerical search to established optimizers. The harness comprises a minimal system
prompt, typed tool definitions, a dispatcher, and a safety-bounded iteration loop, encoding domain knowledge through tool schemas rather than hard-coded logic. CP-
Agent is demonstrated on four case studies: calibrating four slip parameters of additively manufactured stainless steel 316L against tensile data; validating the workflow against published copper
benchmarks, reproducing stress-strain and texture
evolution; recovering the initial crystallographic texture of copper, where the
agent correctly identifies a diffuse initial texture; and reproducing the multi-pass rolling texture
evolution of a Mg-Zn-Ca
alloy, where the
agent chains five deformation passes and recovers the experimentally observed weakened, split basal texture. In all cases, the
agent inferred the correct execution sequence from the task statement, robustly across repeated runs, and delivered physically interpretable results. This work establishes harness engineering as a systematic approach to automating CP modeling workflows while maintaining physical interpretability and auditability through visible
reasoning traces.
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Strongly Correlated Electrons
Quantum Representation Selects Neutral Skyrmion Molecules
Vishnu Jejjala
Skyrmions experience a sideways gyroscopic force when they move. Bound molecules can cancel this force; we call them gyroscopically neutral. We show that the
quantum states available on each site of a magnet select the composition needed for cancellation. In two models of $SU(3)$ magnetism, this composition changes from a pair to a trimer. Both models assign exactly the same energy to every configuration of their common classical order parameter, isolating the effect of the local
quantum states. Neutral molecules can also unwind when additional local states are allowed. Mean field calculations nevertheless find both compositions bound and locally stable, with the neutral trimer surviving sampled interaction changes. Comparing their motion reveals the changed cancellation rule, and prepared neutral molecules translate over short distances with little deformation.
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Strongly Correlated Electrons
A Unified Spin-Fermion Framework for Magnetic Diversity in Chromium Monopnictides
Ruoshi Jiang and Bartomeu Monserrat
Isoelectronic compounds are generally expected to exhibit related electronic, structural, and
magnetic behavior. Chromium monopnictides CrX (X= Sb, As, P), however, display a striking
evolution from high-temperature altermagnetism in NiAs-type CrSb, through double-helical antiferromagnetism in MnP-type CrAs, to the absence of resolved long-range
magnetic order in MnP-type CrP. Here, combining first-principles calculations in the non-collinear Curie-paramagnetic state, structural analysis,
magnetic phase-diagram calculations, and exchange-parameter extraction, we establish a unified microscopic framework for this
evolution. All three compounds share a formal high-
spin $d^5$ configuration, nominally Cr$^{1+}$, coupled to itinerant states of predominantly pnictogen character. From Sb to P, chemical pressure enhances ligand itinerancy and drives the structural
evolution from the high-
symmetry NiAs
lattice to increasingly distorted MnP-type networks. The accompanying reconstruction of competing Cr-Cr exchanges favors A-type antiferromagnetism in CrSb and double-helical order in CrAs, while placing CrP near a frustrated regime with closely competing
magnetic tendencies. Our results establish chemical-pressure-driven exchange reconstruction as a general mechanism through which a common
spin-
fermion electronic structure can generate contrasting
magnetic phases in strongly correlated materials.
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Statistical Mechanics · Cross-listed from quant-ph
Exact Characterization of the Holevo Bound by a Quantum Fisher Information Family
Koji Yamaguchi and Hiroyasu Tajima
The
quantum Cramér-Rao bound constrains the precision of parameter estimation through the symmetric logarithmic derivative
quantum Fisher information (SLD QFI). It is asymptotically achievable for regular single-parameter estimation models, but generally not in the multiparameter setting, where optimal measurements for different parameters may be incompatible. For multiparameter estimation, allowing collective measurements, the corresponding asymptotically achievable precision limit is the Holevo bound, whose standard formulation is an optimization over auxiliary Hermitian operators. We bridge this apparent difference in formulation by giving an exact characterization of the Holevo bound in terms of a family of QFIs interpolating between the SLD and right logarithmic derivative (RLD) QFIs. Specifically, for any locally identifiable finite-dimensional estimation problem, we prove that the operator-feasible region in the standard variational definition of the Holevo bound coincides with the intersection of the regions defined by the corresponding Cramér-Rao-type
matrix constraints for the entire QFI family. This characterization also applies to rank-deficient states and does not require any prior choice of weight
matrix. Consequently, the conventional weight-dependent Holevo bound is recovered by minimizing the corresponding weighted cost over the resulting common feasible region.
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Mesoscale and Nanoscale Physics
Emergent frustrated magnetism in strain-patterned graphene
Yu-Chiang Hsieh, Wen-Han Kao, Christophe De Beule et al. (+18 more)
Geometrically frustrated magnetism conventionally arises from pre-existing
magnetic moments on
lattices whose geometry prevents their interactions from being simultaneously satisfied, giving rise to highly degenerate states and rich collective behavior. Creating such frustration in an intrinsically non-
magnetic material presents a fundamentally different challenge, requiring both the magnetism and the competing interactions to emerge from correlated electrons. Here we show that this can be realized in
graphene through lithographically programmable strain engineering. Patterning strain and the associated pseudo-
magnetic field (PMF) into superlattices creates a correlated electronic system with flat bands and strong interactions. Transport measurements reveal interaction-driven insulating behavior, anisotropic
magnetic hysteresis, and slow relaxation dynamics reminiscent of
spin freezing, qualitatively captured by Monte Carlo simulations of competing
magnetic moments on the PMF-defined ruby superlattice. Cryogenic
magnetic force microscopy further reveals
magnetic textures associated with the PMF landscape. These observations demonstrate frustrated magnetism emerging from correlated electrons in otherwise non-
magnetic graphene. Our results establish lithographic strain engineering as a general and scalable route to flat bands and correlated states in van der Waals materials, providing a versatile platform for programmable
quantum matter.
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All authors Yu-Chiang Hsieh, Wen-Han Kao, Christophe De Beule, Sheng-Zhu Ho, Ru-Long Gou, Bo-Nian Chen, Kuan-Yu Chou, Kuo-En Chang, Chin-Chia Chang, Ying-Mei Yang, Ching-Hua Kao, Hao-Chien Chiang, Jyun-Lin Chen, Sheng-Chin Ho, Kenji Watanabe, Takashi Taniguchi, Ming-Hao Liu, Ching-Hao Chang, Yi-Chun Chen, Ying-Jer Kao, Tse-Ming Chen
Materials Science
Unconventional magnetoelastic behavior in Al rich CoFeAl Films with inverse Heusler like local order for flexible spintronics
Rupalipriyadarsini Chhatoi, Anuroopa Behatha, Swayang Priya Mahanta et al. (+6 more)
Strain engineering of
magnetic properties offers a promising route toward flexible spintronic applications. Here, we report an unconventional magnetoelastic response in Al rich Co Fe Al thin films on flexible substrates using strain dependent magneto optical Kerr effect microscopy and magnetometry measurements. While the films exhibit a conventional positive magnetostriction coefficient, consistent with standard in plane easy axis rotation under stress, their saturation magnetization increases under compressive strain and decreases under tensile strain. First principles calculations reveal that this unconventional response originates from a strain induced competition between exchange splitting and
crystal field effects in an inverse Heusler like local environment created by Al enrichment. This leads to a highly sensitive, sublattice dependent
magnetic state, consistent with a strain induced reconfiguration of Co and Fe moments. Our results demonstrate that local compositional tuning can fundamentally alter magnetoelastic behavior, establishing strain controlled sublattice compensation as a route toward programmable
magnetic functionality in flexible spintronic systems.
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All authors Rupalipriyadarsini Chhatoi, Anuroopa Behatha, Swayang Priya Mahanta, Shubhransu Sahoo, Soubhagya Dash, Bhuvneshwari Sharma, Abhisek Mishra Esita Pandey, Satadeep Bhattacharjee, Subhankar Bedanta
Strongly Correlated Electrons · Cross-listed from quant-ph
Sipser-Spielman meets Dijkgraaf-Witten: non-Abelian qLDPC codes via twisted sheaf gauge theory and almost-constant-overhead magic state fountain
Guanyu Zhu, Shi Jie Samuel Tan, Ryohei Kobayashi et al. (+1 more)
Sipser-Spielman codes and Dijkgraaf-Witten twisted gauge theories are among the most profound ideas in the last few decades in the areas of computer science and mathematical physics respectively. This work unifies them in the same framework using the
language of sheaf cohomology, and produces a new framework of twisted sheaf gauge theories describing a class of
quantum low-density parity-check (qLDPC) codes with non-Abelian $D_4$ topological order. The corresponding twisted Clifford-stabilizer qLDPC code can be obtained from gauging a new type of 0-form sub-complex
symmetry from a qLDPC code defined on a general sheaf complex, and can be interpreted as a topological defect network of non-Abelian $D_4$ patches glued together with proper gapped interfaces. As an application, one can use this to realize a magic state fountain via the gauging measurement of the addressable logical CZ gates as 0-form subcomplex
symmetries in a 2D hypergraph-product (HGP) sheaf code. This includes a scheme of subdividing an arbitrary constant-rate 2D HGP code with parameters $[[n,\Theta(n), \Omega(n^{1/2})]]$ into a
quantum sheaf code which allows preparation of $\Theta(n^{1/2})$ logical CZ magic states in parallel, equivalent to the recent
geometric construction using the code-to-
manifold mapping in (arXiv:2601.06736). Moreover, using the recent sheaf complex and algebraic code constructions by Golowich-Tamo-Zhu (arXiv:2609.27801) with parameters $[[n,\Theta(n^{1-\epsilon}), \Omega(n^{(1-\epsilon)/2})]]$ for arbitrary small $\epsilon$, one can prepare $\Theta(n^{1-\epsilon})$ CZ magic states in parallel and hence achieve an almost-constant magic rate.
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All authors Guanyu Zhu, Shi Jie Samuel Tan, Ryohei Kobayashi, Po-Shen Hsin
Materials Science
Structural prediction of B$_{18}$Y$_{2}$ cluster: A Machine-Learning-Assisted Basin-Hopping Study
Peter Ludwig Rodríguez-Kessler
The structural and optical properties of the doubly yttrium-doped boron cluster B$_{18}$Y$_2$ have been systematically investigated using density functional theory calculations. The lowest-energy structure was identified through extensive basin-hopping searches accelerated by a pre-trained MACE machine-learning potential and subsequently refined and validated at the DFT level. The resulting global-minimum structure adopts a double-ring geometry, consisting of two fused B$_9$ rings stabilized by yttrium atoms positioned above and below the boron framework. Vibrational frequency calculations confirm the dynamical stability of the optimized structure, while the calculated infrared and UV–Vis spectra provide characteristic signatures of the Y–B interactions and the electronic structure of the boron framework. These results demonstrate how yttrium doping can stabilize unusual double-ring boron architectures and highlight the effectiveness of machine-learning-assisted basin-hopping searches for exploring the complex potential-energy landscapes of doped boron clusters.
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Materials Science · Cross-listed from physics.acc-ph
Fabry-Pérot Resonance Shifts as a Novel Non-destructive In Situ Surface Damage Diagnostic
Gregory Blume, Colin Kirk, Sushil Poudel et al. (+6 more)
Current surface damage evaluation for nanostructured electronic devices requires specialized equipment or conditions outside the designed operating environment and cannot be used for in situ evaluation of surface damage. In this work, we developed a non-destructive method to probe the surface sublimation of a
semiconductor heterostructure which can be applied to other
semiconductor damage mechanisms. This approach employs shifts in the resonances of an optical cavity comprising the surface and an integrated distributed Bragg reflector fabricated below the
semiconductor heterostructure undergoing sublimation. We performed the demonstration of this technique under
vacuum, but surface damage effects can be observed in any operational environment either in situ or ex situ.
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All authors Gregory Blume, Colin Kirk, Sushil Poudel, John Hill, Alimohammed Kachwala, Joseph Grames, Marcy L. Stutzman, Matt Grau, Sylvain Marsillac
Statistical Mechanics
Complexity drives the symmetry breaking of temperature fluctuations
D. Rosales Herrera, M. Y. Gallegos Ruiz, A. Fernández Téllez et al. (+2 more)
Frequently, nonextensive systems are described through $q$-exponential functions, where the $q$-parameter determines how far a system is from
equilibrium. In this work, we study systems constrained to $q-1\ll1$ to describe systems near thermal
equilibrium, and derive the probability density function and temperature fluctuations. To this end, we derive the series expansion of the $q$-exponential function, yielding a perturbative series that is a superposition of gamma distributions. On the other hand, the temperature fluctuations are expressed as a superposition of Dirac delta functions and their derivatives, meaning that the bulk of the system remains at a constant temperature, while point-temperature variations emerge, marking the system's departure from thermal
equilibrium. The statistics of the temperature fluctuations exhibit a transition from a symmetric to a nonsymmetric distribution as the nonextensive parameter increases. These results provide evidence of the association between the emergence of nonextensivity and the
symmetry breaking of temperature fluctuations.
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All authors D. Rosales Herrera, M. Y. Gallegos Ruiz, A. Fernández Téllez, J. R. Alvarado García, J. E. Ramírez
Materials Science
Retrainable physics-integrated neural differentiable modeling of sintering across material systems
Zeping Chen, Ani Aprahamian, Khachatur V. Manukyan et al. (+1 more)
Sintering is widely used to manufacture ceramics, but coupled densification and grain growth, material-dependent kinetics, and sparse measurements complicate predictive modeling and process design. We present Sinter-PiNDiff, a retrainable physics-integrated neural differentiable framework for predicting density and grain-size
evolution. Two neural networks learn densification and grain-growth coefficients within coupled rate equations, while a smooth saturation factor attenuates densification near theoretical density. The same governing structure, network architecture, and training procedure were fitted independently to published data for MgO, Al-doped ZnO, and CaO-doped ThO2. Tests at held-out temperatures and compositions yielded the lowest mean error in all twelve material-metric comparisons against multilayer perceptron and residual network baselines. For MgO, Al-doped ZnO, and CaO-doped ThO2, respectively, density normalized root-mean-square errors were 14.6%, 10.8%, and 14.4%, and grain-size errors using the same metric were 8.6%, 12.1%, and 19.3%. Removing evolving density from both neural-network inputs increased density and grain-size trajectory errors in all three systems and ten of twelve aggregate errors, supporting density-dependent kinetic feedback. Deep ensembles estimated model disagreement, but empirical coverage showed that the uncertainty bands were not calibrated and did not capture all model-data discrepancies. These results establish Sinter-PiNDiff as a retrainable framework for sparse-data prediction and uncertainty-informed selection of sintering conditions.
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All authors Zeping Chen, Ani Aprahamian, Khachatur V. Manukyan, Tengfei Luo
Strongly Correlated Electrons · Cross-listed from hep-th
Bound States in 2d Yukawa Theory from Hamiltonian Truncation
Olivier Delouche, Kara Farnsworth and Francesco Riva
We study the spectrum of two-dimensional Yukawa theory using
Hamiltonian truncation, with a focus on bound states. We extend the framework of
Hamiltonian truncation effective theory to include
fermions and logarithmic UV divergences. With these corrections, the energy levels converge as a function of the cutoff with the scaling predicted by power counting. We identify a strategy to follow the
evolution of
fermion-antifermion bound states from weak to strong coupling, and investigate its binding energy, finding good agreement with finite-volume perturbation theory at weak coupling. Finally, we explore the heavy-scalar regime toward the massive Thirring/Sine-Gordon limit, recovering the expected weak-coupling behavior and outlining how the calculation can be extended toward this limit.
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Mesoscale and Nanoscale Physics
Rydberg excitons in core-shell nanostructures II. Plasmon-exciton interaction and enhancement
David Ziemkiewicz, Gerard Czajkowski and Sylwia Zielińska-Raczyńska
Interaction between Rydberg
excitons in core-shell Cu$_2$O nanostructures and surface plasmons is investigated. An enhancement of a quadrupole transitions to the Rydberg
exciton states in copper oxide plasmonic nanaostructures is examined. A possibility of a modification of plasmonic enhancment (i.e., an average amplification factor) of electric field distributions in the vicinity of nanostructures, which depends on its shape and geometrical size, is also discussed.
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Materials Science · Cross-listed from physics.chem-ph
HOMO-LUMO Intervals from Modern Density Functionals as Fundamental Gap Estimators
H. Francisco, Javier Carmona-Espíndola, A. C. Cancio et al. (+2 more)
Use of the Kohn-Sham
eigenvalue gap (highest occupied molecular orbital to lowest unoccupied, HOMO-LUMO) as a fundamental gap (I-A, I= ionization potential, A= electron affinity)
estimator is a long-standing challenge for relatively simple exchange-correlation functionals, e.g. meta-GGAs. The LAK meta-GGA [T. Lebeda et al. Phys. Rev. Lett. 133, 136402 (2024)] was developed to emphasize certain constraints in ways intended to make the LAK KS gaps close to the HSE06 hybrid functional [A.V. Krudau et al. J.Chem. Phys. 125, 224106 (2006)] gaps. The LAK functional was tested against a small atomization data set and a very small bond length set, with no molecular HOMO-LUMO gap testing. Here we test LAK against widely used, large reference data sets for molecular heats of formation, bond lengths, harmonic frequencies, I, and A and compare with r2SCAN [J.W. Furness et al., J. Phys. Chem. Lett. 11, 8208 (2020)] as well as HSE06 and PBE0, a quite different hybrid. On these tests LAK does not give meaningfully better geometries, heats of formation, HOMO-LUMO gaps, or DFT IP
theorem satisfaction than r2SCAN. Compared against experimental I and A values the same holds; LAK results resemble r2SCAN results, not HSE06. Moreover, the HOMO and LUMO shifts generated by the NCAPR GGA [J. Carmona-Espindola et al., J. Chem. Phys. 157, 114109 (2022)] as derivative discontinuity estimates, correct the bare NCAPR HOMO and LUMO
eigenvalues to substantially better agreement with experiment for both fundamental gap and IP
theorem than do the meta-GGAs (LAK, r2SCAN) or hybrids (HSE, PBE0). We discuss possible reasons why LAK behaves differently for molecules and solids.
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All authors H. Francisco, Javier Carmona-Espíndola, A. C. Cancio, José Luis Gázquez, S. B. Trickey
Materials Science
Crystallographic-orientation dependence of the early-stage oxidation of Zr single crystals: an XPS study of suboxide formation and in-depth distribution
Joaquin Sacanell and Flavio Conde
The influence of crystallographic orientation on the early stages of the oxidation of pure Zr single
crystals was studied by X ray photoelectron spectroscopy (XPS). Two samples, cut from the same a-Zr single
crystal, were oxidized simultaneously at room temperature and O2 pressures of 1 X 10-8, 1 X 10-7 and 1 X 10-6 torr: one with its surface normal parallel to the c-axis (Z1, basal (0001) plane) and the other with its normal 12deg from that of a prismatic plane (Z2, near-prismatic orientation). At all three pressures the oxidation kinetics of both samples followed a three stage, logarithmic type behaviour, but the near prismatic sample (Z2) incorporated oxygen faster and to a greater extent than the basal sample (Z1) in every case. Deconvolution of the Zr 3d core level spectra resolved, in addition to metallic Zr and ZrO2, two sub-stoichiometric Zr O compounds, denoted (ZrO)a and (ZrO)b, with binding-energy shifts of 1.3 and 2.3 eV with respect to metallic Zr, consistent with sub oxides previously reported for polycrystalline Zr. Angle resolved XPS showed that ZrO2 is the outermost compound in both orientations, while the two sub-oxides are distributed nearly homogeneously through the film. Oxide thicknesses, calculated from the attenuation of the metallic Zr 3d signal, ranged from 10 to 13 A for Z1 and from 14 to 19 A for Z2 depending on the oxidation pressure, in close agreement with earlier measurements on cold worked polycrystalline Zr, whose surface texture is dominated by prismatic-oriented grains.
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Materials Science · Cross-listed from physics.chem-ph
Scaling Density Functional Theory with Gaussian Splatting
Andrés Guzmán-Cordero, Cindy Zhang, Majdi Hassan et al. (+3 more)
Density functional theory (DFT) strikes a practical balance between accuracy and computational cost in many problems of computational chemistry and materials science. However, many DFT calculations are limited by fixed atom-centered basis sets, which dictate how accuracy and cost scale with system size. We propose Gaussian Splatting for Density Functional Theory (GS-DFT), which represents molecular orbitals as a cloud of Gaussians whose positions, shapes, and mixing coefficients are optimized jointly by gradient descent to minimize the energy without training data. Conceptually, GS-DFT is 3D Gaussian splatting with the renderer replaced by
quantum mechanics. We introduce two key solver components: adaptive density fitting with screening for efficient evaluation of two-electron integrals, and a regularized differentiable orthogonalization of the molecular orbitals. Empirically, the optimized basis reaches the accuracy of the largest conventional basis sets with a fraction of the parameters, converging systematically in energy, density, and nuclear forces. At equal parameter count, it captures the stretched-bond and anion physics that fixed bases only recover with specialized basis augmentation. The resulting solver exhibits quadratic peak
memory scaling in the cloud size, allowing us to simulate systems of up to 2,742 atoms (10,406 electrons) without any modifications at triple-zeta scale using a single four-GPU node.
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All authors Andrés Guzmán-Cordero, Cindy Zhang, Majdi Hassan, Marta Skreta, Kirill Neklyudov, Matija Medvidović
Materials Science
Ferroelectric Switching in ZnO/Zn1-xMgxO Heterostructures: Atomistic Insights into Interfacial Coupling and Layer Architecture
Alireza Sepehrinezhad, Ali Mohammadi Dinani, Ece Gunay et al. (+4 more)
Ferroelectric switching in
heterostructures couples composition, layer
topology, temperature, and interfacial boundary conditions. ReaxFF molecular dynamics isolates these variables in ZnO/ Zn1- xMgxO/ZnO and Zn1-xMgxO/ZnO/ Zn1-xMgxO stacks. Within pristine, initially single-domain models, coupling to switchable Zn1-xMgxO reduces the applied field required to reverse ZnO by up to fivefold. Temperature generally lowers the coercive field, whereas Mg concentration produces a nonmonotonic response. At equal ZnO and Zn1-xMgxO (ZMO) proportions, structures with ZnO at the center switch at lower fields than those with ZMO at the center at all four temperatures examined, demonstrating a
topology-dependent response. Layer-resolved trajectories reveal
topology-dependent switching sequences with direction-dependent redistribution of normal stress near the heterointerfaces, consistent with a stress-assisted cooperative pathway. Limiting MgO-containing structures exhibit sequential multilevel switching or low-polarity trapping, depending on thickness and temperature. Fixed-charge atomistic simulations complement previous continuum descriptions by resolving structural, energetic, and local stress
evolution under a common applied field. TEM and STEM-EDS observations provide experimental structural context for the modeled architectures. Together, the results establish layer
topology and interfacial mechanical confinement as design variables for wurtzite ferroelectric
heterostructures.
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All authors Alireza Sepehrinezhad, Ali Mohammadi Dinani, Ece Gunay, Elizabeth C. Dickey, Jon-Paul Maria, Susan Trolier-McKinstry, Adri C.T. van Duin
Quantum Gases
Spatiotemporal Non-Hermitian Skin Effect with Floquet-Engineered Ultracold Atoms
Weijie Liang, Weiping Zhang and Keye Zhang
Non-Hermitian skin effect, the accumulation of bulk eigenstates at edges under open boundary conditions, has been observed across classical,
quantum, and synthetic platforms. Whether it can be generalized to the genuine time dimension remains open. We propose a spatiotemporal NHSE in the Floquet phase space via Floquet engineering of a ring-trapped ultracold atomic gas. Placing spatial and temporal degrees of freedom on an equal footing, we show that a single parent skin effect projects onto either domain. The spatial projection yields an NHSE with arbitrarily tunable skin locations, eliminating the need for physical open boundaries. The temporal projection gives time-domain nonreciprocity and periodic temporal funneling, consistent with causality. This establishes a unified spatiotemporal paradigm for NHSE and opens a route to non-Hermitian topological physics in time.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Nonstabilizerness of quantum tensor network states is intractable in two dimensions
Gianluca Esposito and Georgios Styliaris
Nonstabilizerness is a necessary resource for
quantum systems to lie beyond the classically simulable regime. With the advent of stabilizer $\alpha$-Rényi
entropies, nonstabilizerness has also become a many-body diagnostic, complementary to
entanglement. While deciding whether an arbitrary
quantum state has nonstabilizerness is provably hard, such states already require a description exponentially large in the number of
qubits and are thus out of reach for many-body physics. Here we instead consider 2D tensor network (TN) states, which compactly capture states obeying an
entanglement area law, and ask whether they admit a simpler
algorithm for the same task. In contrast to the 1D case, we prove that, even at small, constant bond dimension, computing the stabilizer
entropy of 2D TN states is $\#\mathrm{P}$-hard for any integer $\alpha\ge 2$, and deciding stabilizer membership is $\mathrm{C_=P}$-complete. The corresponding constant-accuracy problems remain $\mathrm{C_= P}$-hard. We further prove that deciding whether a PEPS can be transformed into a stabilizer state by local
unitaries over a specified bipartition is $\mathrm{C_= P}$-hard. Under standard complexity assumptions, these results rule out classical or
quantum algorithms with
polynomial resources for all three tasks in the worst case.
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Materials Science · Cross-listed from physics.optics
High-Yield, 150 ps Polymer Scintillators via Synergistic Purcell and High-Z Enhancement
Xiaohe Zhou, Hiba H. Karakkal, Chenger Wang et al. (+12 more)
Developing plastic scintillators that simultaneously achieve high light yield (LY), ultrafast timing, and scalable processability remains a formidable challenge in radiation detection. Here, we report a solution-processable hybrid scintillator that integrates high-Z sensitization with Purcell-enhanced radiative recombination within a conjugated-
polymer platform. By
embedding HfO2 nanoparticles and resonant Ag-SiO2 plasmonic nanoantennas into a poly(9,9-dioctylfluorene)
matrix, we exploit the intrinsic sub-nanosecond kinetics of conjugated
polymers while overcoming their characteristic low stopping power. The HfO2 nanocrystals amplify energy deposition and suppress interchain aggregation, preserving high photoluminescence
quantum yields in the solid state. Simultaneously, the nanoantennas induce strong plasmon-
exciton coupling, accelerating radiative decay to ~150 ps. This synergistic architecture yields LY=6.1
photons/keV, comparable to standard commercial plastics with nanosecond lifetimes, yet over an order of magnitude higher than current sub-nanosecond state-of-the-art materials. This performance represents one of the most favourable combinations of efficiency and timing resolution reported to date. Our versatile strategy provides a framework for next-generation organic scintillators, merging record-breaking temporal response with high efficiency for advanced radiation-sensing architectures.
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All authors Xiaohe Zhou, Hiba H. Karakkal, Chenger Wang, Andrea Fratelli, Francesco Bruni, Matteo L. Zaffalon, Leonardo Poletti, Saptarshi Chakraborty, Emanuele Mazzola, Roberto Lorenzi, Francesco Carulli, Francesca Rossi, Francesco Meinardi, Luca Gironi, Sergio Brovelli
Mesoscale and Nanoscale Physics
Maximal Chern Numbers from Finite-Range Hopping
Christopher Arriagada Cortés and Vladimir Juričić
Finite-range hopping constrains both the number of Dirac points and the masses that gap them. We determine the maximal absolute Chern numbers of an isotropic finite-range extension of the Qi–Wu–Zhang model on a square
lattice through thirteenth-neighbor hopping. Algebraic zero counting and mass-weighted sum rules yield global bounds, and we construct explicit
Hamiltonians that saturate them. We find $|C|_{\max}=36,40,51$ for eleventh-, twelfth-, and thirteenth-neighbor hopping. Equal numbers of Dirac points can produce different maxima because finite-range mass harmonics distinguish opposite
vortex charges differently. Twice the squared hopping radius bounds every maximum through twelfth-neighbor hopping and is saturated at the eleventh and twelfth, but the thirteenth-neighbor maximum exceeds it. Thus finite-range hopping constrains the maximal Chern number in two complementary ways: through the number of Dirac
vortices it can generate and through the mass-sign patterns it can assign to them. This
geometric viewpoint provides a design principle for high-Chern bands and a route to analogous bounds in moiré and other
lattice systems.
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Materials Science
Dielectric response of the antiferromagnetic multiferroics with cycloidal equilibrium for the polarization related to the noncollinear spins
Pavel A. Andreev
Linear dynamics of the small amplitude perturbations in the antiferromagnetic multiferroics is analytically considered.
Equilibrium state in the considered regime is assumed to be cycloidal structure both for the antiferromagnetic vector and the nonzero magnetization vector (presence of weak ferromagnetism in the system is included). The electric polarization of
spin origin related to the "noncollinear"
spins is considered and its influence on the
spin dynamics is included. The dynamical electric susceptibility tensor is obtained to demonstrate response of the multiferroics on the alternating electric field. Existence of two polarization projections is found, response of each of them on two projections of the electric field perpendicular to the cycloid direction is presented. Different roles of the in plane and out of plane electric perturbations is demonstrated analytically. Essential role of the low frequency gapless
spin wave in the dielectric response is described. Contributions of the spiral structure and the weak ferromagnetism in the dielectric response are specified.
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Other Condensed Matter
Non-Uniform Quantum Well and Barrier Thickness Engineering for Robust Ultra-High TER and Low RA Ferroelectric Tunnel Junctions
Balram Khattar, Adarsh Tripathi, Manish Anand et al. (+1 more)
HfO$_2$-based ferroelectric tunnel junctions (FTJs) are promising candidates for scalable non-volatile
memory, but simultaneously achieving a high tunneling electro-resistance ratio (TER) and a low resistance-area (RA) product remains challenging. To address this challenge, this work introduces non-uniform
quantum well (QW) and barrier thickness engineering in HfO$_2$-based multi-QW FTJs using a self-consistent Preisach-based ferroelectric (FE) model integrated with the coherent and inelastic non-
equilibrium Green's function (NEGF) formalism. The non-uniform well and barrier configuration produces a wide range of FTJ design landscapes due to closely spaced, broad resonant states in the low resistance state (LRS) and a larger separation in the high resistance state (HRS), resulting in strong polarization-dependent resonant transmission with TER reaching the order of $\mathbf{1\times10^{8}\%}$ and an LRS RA product as low as $\mathbf{1~\Omega\cdot\mathrm{cm}^{2}}$ at read bias and in the presence of scattering. By incorporating self-consistent elastic scattering into the NEGF framework, we also show that elastic scattering can positively influence the TER and RA performance of non-uniform FTJs by progressively increasing the overlap of the closely spaced resonances. Overall, the results establish non-uniform QW and barrier thickness as an effective and robust design parameter for controlling resonant-state
alignment and achieving a favorable combination of high TER and low RA in HfO$_2$-based multi-QW FTJs.
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All authors Balram Khattar, Adarsh Tripathi, Manish Anand, Abhishek Sharma
Materials Science
Polar discontinuity screening by charge disproportionation in ferroelectric-nickelate superlattices
Edith Simmen, Jonathan Amara, Philippe Ghosez et al. (+1 more)
We use density functional theory (DFT) to demonstrate rearrangement of charge disproportionation as a new mechanism for screening polar discontinuities at heterointerfaces. We focus on SmNiO$_3$, a III-III perovskite characterized by an insulating ground state that originates from disproportionation of the electrons at the Ni sites. When interfaced with ferroelectric, II-IV perovskite BaTiO$_3$, this system can display a polar discontinuity whose magnitude is determined by the nature of the interface (NiO$_2$-BaO or SmO-TiO$_2$) and the orientation of the BaTiO$_3$ spontaneous polarization. In the orientation maximizing the interface charge, SmNiO$_3$ compensates by transferring 1 $e$/f.u. between the two interfaces and modifying the disproportionation sequence from Ni$^{4+}$/Ni$^{2+}$ to Ni$^{2+}$/Ni$^{2+}$ at the SmO-TiO$_2$ interface and to Ni$^{4+}$/Ni$^{4+}$ at the NiO$_2$-BaO interface. While this mechanism is potentially universal in all perovskites exhibiting charge disproportionation, our formal analysis of BiNiO$_3$/BaTiO$_3$ superlattices suggests that larger polar discontinuities may need more complex disproportionation patterns for screening.
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All authors Edith Simmen, Jonathan Amara, Philippe Ghosez, Nicola A. Spaldin
Materials Science
A quantitative phase-field model for grain boundary trapping and diffusion of hydrogen
Vincent Feyen, Martin Diehl and Nele Moelans
Grain boundaries influence hydrogen transport in polycrystalline metals by acting as both trapping sites and interconnected
diffusion pathways. Conventional interpretations of thermal desorption spectroscopy (TDS) and permeation experiments often treat traps as isolated defects, neglecting grain boundary connectivity and potentially misinterpreting experimental data. Here, we develop a quantitative phase-field model for hydrogen
diffusion, grain boundary trapping, and grain boundary-assisted transport. The formulation preserves the physical grain boundary volume independently of the numerical interface thickness and accounts for anisotropic
diffusion parallel and perpendicular to grain boundaries.
Benchmark simulations verify quantitative behavior under interface upscaling. The model shows that grain boundary
diffusion can significantly shift TDS peaks, making Kissinger-type analyses unreliable when grain boundary transport is significant. Effective
diffusion coefficients are also shown to depend strongly on grain size, trapping free energy, temperature, and grain boundary mobility. These results highlight the coupled role of trapping thermodynamics, bulk
diffusion, and grain-boundary transport.
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Strongly Correlated Electrons · Cross-listed from math-ph
Categorical spin-networks: state-sum invariants of 4-manifolds from higher-gauge theory
Hank Chen, Zhian Jia, Ran Luo et al. (+1 more)
In this work, we define $(3+1)$-dimensional topological
quantum field theories (TQFTs) and their
lattice realizations with input data given by a pivotal fusion 2-category; more precisely, our framework applies in wider generality to presemisimple locally fusion pivotal tensor $2$-categories, which are equipped with a so-called shadow trace. We introduce a decoration of triangulated
manifolds by the input data, and develop a $20j$-symbol formalism for computing 4-simplex scattering amplitudes. We verify the topological invariance of 20$j$-symbol summations under the 4-dimensional Pachner moves. Furthermore, we also construct explicitly a 3-dimensional Levin-Wen-type
lattice Hamiltonian model realizing the state-sum invariant. Our construction can be understood as a higher-dimensional analogue of the
spin-networks construction for the Turaev-Viro invariant. Examples arising from $2$-groups are discussed from the perspective of higher gauge theory.
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All authors Hank Chen, Zhian Jia, Ran Luo, Wei Cui
Statistical Mechanics
The memory equation of a characteristic function in surface diffusion
S. Miret-Artés
The decay of a density wave, the
Fourier component of the adparticle density seen by a coherent probe, obeys in an interacting adlayer an exact
memory equation of Mori's form, determined by the local rate and the
memory function. Because the density is conserved, the correlation function is a characteristic function, and the kernel is built from that of a single jump; positivity and normalization then make the local rate and the
memory function
equilibrium averages, whatever the interaction. The local rate obeys an exact sum rule, which makes de Gennes narrowing a
theorem on the
lattice and gathers the interaction into one effective hop rate. Detailed balance makes the decay a superposition of relaxation modes, approached from below by a convergent hierarchy of closed forms. The theory fixes the local rate, the
memory function and the relaxation spectrum. The experiment provides the static structure factor and the decay, recorded from the instant of scattering through a ballistic regime, a jump regime in which the
memory acts, and a diffusive regime. A single exponential fitted, as experiments do, over a time interval in the diffusive regime gives the slowest relaxation rate, the constant rate of that regime, and not the local rate. The correlation time, defined as the area beneath the normalized decay, needs no time interval and is the mean inverse relaxation rate. Under a standard condition on the jump rates, met in one-dimensional
diffusion when the rate of leaving a site is independent of the site reached, the correlation time, the static structure factor and the
lattice geometry give the effective hop rate at long wavelength, with no model or fit and with a parameter-free test. There the sum rule becomes a Darken-type relation.
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Strongly Correlated Electrons
Criticality enabled long-range order in a U(1)-symmetric spin-1 Heisenberg chain with biquadratic interactions
Natalia Chepiga and Fabian H.L. Essler
In a recent paper Nahum argued on the basis of a renormalization-group analysis that, contrary to standard lore, ground states of 1D
spin chains with short-range interactions can spontaneously break U(1) “easy-plane”
spin rotation
symmetry. True long-range order of $(S^x,S^y)$ arises at the phase transition between two quasi-long-range-ordered phases. Here we present detailed numerical results for an anisotropic
spin-1 chain model. We find a magnetization exponent $\beta\approx0.29$, consistent with the $\epsilon$-expansion prediction $\beta\approx0.28$, a divergence of the Luttinger parameter on approaching the transition from both sides with an exponent that we relate to Nahum's transition, and finite-size spectra consistent with a dynamical critical exponent $z\approx2$. Our results support the critical behavior predicted by Nahum's field theory.
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Quantum Gases · Cross-listed from physics.atom-ph
Highly elastic collisions of ultracold asymmetric top molecules in a static electric field
Reuben R. W. Wang
We propose that the application of static electric fields to reactive CaNH$_2$ molecules can result in large ratios of elastic to lossy collisions at ultracold temperatures. In the first rotationally excited
manifold, the asymmetric top structure of CaNH$_2$ results in a $\approx 226$ MHz splitting of the opposite parity $K$-doublet states. This modest splitting allows electric fields below a kilovolt per centimeter to polarize the molecules and induce long-range dipole-dipole interactions. By increasing the electric field, we find that dipole-dipole attraction can become sufficiently large to induce weakly bound octatomic field-linked states of [CaNH$_2$]$_2$. In the absence of these field-linked states, we identify select molecular states where dipolar interactions allow elastic collisions to dominate over lossy collisions by up to three orders of magnitude, while maintaining loss rate coefficients at the $10^{-14}$ cm$^3$s$^{-1}$ level. These results establish that evaporative cooling is a viable route to
quantum degenerate gases of
laser coolable asymmetric top molecules. Access to such low
entropy ensembles of asymmetric top molecules holds promise to push the frontiers of
quantum simulation, state-resolved chemistry, and searches for beyond the Standard Model physics.
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Mesoscale and Nanoscale Physics · Cross-listed from quant-ph
Quantum environment afterglow from broadband excitation spectroscopy in superconducting qubits
J. R. Guimarães, Y. Liu, Y. Gao et al. (+10 more)
Understanding the
qubit environment is central to fault-tolerant superconducting
quantum computation. Characterization typically relies on relaxation, leaving excitation largely underexplored. Here, we access this information with time-resolved broadband excitation spectroscopy. The resulting
qubit excitation spectrum reveals a highly structured landscape, interspersed with cold regions. Combined with postselection, this technique enables full reconstruction of the noise power spectral density (PSD) and separates
quantum from classical noise. With feed-forward, it exposes long-lived two-level-systems (TLSs), whose relaxation times span tens of microseconds to milliseconds - uncovering an intrinsic link between the
qubit-TLS coupling and TLS relaxation. The data suggest that the long-lived TLSs are intrinsic to the
qubit environment, and can cause excitation that lasts for many
qubit operation cycles. Consequently, the environment retains a
memory of prior dynamics, and properties like gate fidelity become non-Markovian and protocol-dependent. The presented approach enables identifying and bypassing the hidden roadblocks formed by long-lived TLSs in fault-tolerant
quantum computation.
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All authors J. R. Guimarães, Y. Liu, Y. Gao, Y. Haddad, A. Galicia, D. A. Volkov, J. T. Schmieder, H. Bhardwaj, M. Neis, J. Cereijo, M. Jerger, P. A. Bushev, R. Barends