Materials Science · Cross-listed from physics.chem-ph
Atomic-scale structure of static screening in noble-metal nanoparticles from clusters to the conductor limit
Pulkit Joshi and Marek Sierka
The static screening response of a metallic nanoparticle is encoded in its induced charge density. Integrated observables such as the dipole moment or the polarizability do not determine this density, because many different screening profiles yield the same integrals. We show that in noble-metal nanoparticles the screening charge is atomically structured, with facet, edge, and vertex sites responding differently from a smooth classical conductor. This structure survives in a surface layer of about one atomic width even when the integrated response has reached the conductor limit, and it is absent from continuum descriptions. To resolve it across size, morphology, and composition, we calibrate an atomistic charge-dipole model for Ag and Au nanoparticles directly to first-principles induced-density profiles. The calibration includes the short-range kinetic and exchange-correlation contribution to the hardness kernel that a purely electrostatic model omits, reducing the induced-density-profile error by about a factor of 2.5. A single averaged parameter set per element predicts clusters withheld from the fit and transfers without adjustment to Ag/Au core-shell, alloyed, and elongated particles. A continuous fast multipole implementation of the model scales almost linearly with the number of atoms and reaches several-million-atom particles, far beyond the reach of first-principles methods.
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Materials Science
Photoresponse properties of single-crystalline thick film based on high-entropy topological insulator (Bi3/4Sb1/4)2(Te2/5Se2/5S1/5)3
Alexei Vasilev, Marina Zhezhu and Oleg Ivanov
High-
entropy topological
insulator (Bi3/4Sb1/4)2(Te2/5Se2/5S1/5)3 has been for the first time prepared by self-propagating high-temperature synthesis and melting methods. Single-crystalline thick-filmed sample with thickness of ~0.1 mm was applied to examine the photoresponse properties by using room-temperature chopped-light technique. Photodetector based on (Bi3/4Sb1/4)2(Te2/5Se2/5S1/5)3 demonstrated strong photovoltaic response under irradiation of a white LED light, covering 420-730 nm range. The photocurrent increases from ~20 to ~55 mkA with the increase in intensity from 100 to 600 W/m2 that is originated from the increase in the number of non-
equilibrium carriers generated by light. Room-temperature responsivity and detectivity of the photodetector are ~8.7 mA/W and ~109 Jones, respectively.
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Soft Condensed Matter
Dense HeLa cell monolayers remain liquid-like despite strong crowding
Suravi Pal, Nen Saito, Takeshi Kawasaki et al. (+1 more)
Collective dynamics in dense
cell monolayers are governed by the interplay between crowding and cellular motility. Although increasing density can slow cellular motion and promote glass-like behaviour, the dynamical state of dense HeLa monolayers remains unclear. Here, we combine in vitro time-lapse imaging of HeLa
cell monolayers with simulations of a deformable active-
cell model to examine how
cell density and motility regulate collective relaxation. Within the experimentally accessible density and time ranges, untreated HeLa monolayers remain
liquid-like: structural relaxation progressively slows down with increasing density but remains observable throughout the investigated range. Under low-nutrient conditions,
cell motility is strongly reduced, and structural relaxation becomes substantially slower. To elucidate the mechanisms underlying these experimental observations, we further performed simulations using a deformable-
cell model. The model qualitatively reproduces the density-dependent increase in structural relaxation time and further shows that reducing self-propulsion promotes long-lived caging dynamics at high packing fractions. These results show that dense HeLa monolayers can sustain slow, heterogeneous, yet relaxing collective dynamics under untreated conditions, and indicate that persistent cellular motility is an important factor in maintaining structural relaxation at high density, which may provide insight into the metastatic potential of cancer
cells.
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All authors Suravi Pal, Nen Saito, Takeshi Kawasaki, Hiroyuki Ebata
Statistical Mechanics
Recent progress on thermal transport in one-dimensional long-range interacting Fermi-Pasta-Ulam-Tsingou lattice systems
Daxing Xiong, Nianbei Li and Jie Chen
Long-range (LR) interactions are no longer just a theoretical idea: they can be engineered in several low-dimensional platforms and offer a new way to control heat transport. At the same time, they push beyond the standard picture developed mainly for short-range, momentum-conserving
lattices. In this review, we consider one-dimensional Fermi-Pasta-Ulam-Tsingou (FPUT)-type
lattices where LR effects enter mainly through a quartic anharmonic coupling that decays as a power law, characterized by an exponent {\sigma}. Our goal is to explain, in a unified way, how LR anharmonicity changes microscopic energy exchange, collective dynamics, and the macroscopic scaling laws of heat conduction-while also clarifying what is well established and what is still debated (For more details of the abstract, please see the main text and paper).
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Strongly Correlated Electrons
Exact and fast series expansions for quantum models with long-range interactions
Antonia Duft, Patrick Adelhardt, Jan Alexander Koziol et al. (+2 more)
Over the past decade, high-order series expansions based on linked-cluster methods have become an important tool for studying low-energy properties of gapped
quantum systems with long-range interactions. We introduce a deterministic framework that removes a central computational bottleneck of this method. Our graph zeta method replaces the costly and statistically noisy Monte Carlo (MC) evaluation of high-dimensional
lattice sums by a systematic, high-precision computation that delivers series coefficients within minutes on standard desktop hardware. The full momentum-dependent series is obtained in a single calculation, enabling high-resolution excitation spectra throughout the Brillouin zone. Building on the companion paper [1], the method reformulates graph-
embedding sums as graph zeta functions and decomposes them into blocks classified by their treewidth tw. Low-treewidth blocks (tw$\leq2$) admit closed expressions based on Epstein zeta functions, while higher-treewidth blocks (tw$>2$) are evaluated using tensor-network bucket elimination. We
benchmark the approach for transverse-field Ising models with power-law interactions in 1d, 2d, and 3d, reproducing previous MC results at a fraction of the computational cost while enabling substantially denser parameter sampling. An open-source implementation makes the method directly applicable to general interactions and large parameter scans. As an application, we compare microscopic interaction models for the stacked quasi-2d transverse-field Ising triangular-
lattice antiferromagnet KTmSe$_2$ and find that a model including dipolar interactions best describes existing experimental data. The graph zeta method thus turns high-order linked-cluster expansions into a practical and deterministic tool for fast quantitative momentum-resolved modeling of short- and long-range
quantum matter.
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All authors Antonia Duft, Patrick Adelhardt, Jan Alexander Koziol, Andreas A. Buchheit, Kai Phillip Schmidt
Strongly Correlated Electrons
Electronic correlations shape the low-energy optical response of the kagome antiferromagnets Mn$_3$Sn and Mn$_3$Ge
R. Mathew Roy, Bo Tai, Maxim Wenzel et al. (+7 more)
Using optical spectroscopy and density functional theory, we provide evidence that electron-electron interactions strongly affect the properties of the kagome antiferromagnet Mn$_3$Sn, since its low-energy optical interband transitions arise exclusively from the correlation-modified electronic band structure. Mn$_3$Sn possesses an optical effective mass about three times larger than that of its isostructural analog Mn$_3$Ge. The DFT+$U$ treatment in the Lichtenstein formulation, with an on-site Coulomb repulsion $U = 4$~eV and Hund's coupling $J = 0.25$~eV, accounts for the optical transitions in Mn$_3$Sn, whereas those in Mn$_3$Ge are already reproduced without Hubbard corrections ($U, J = 0$). The near-isotropic electronic structure of Mn$_3$Sn reveals a three-dimensional metal whose electronic response is shaped prominently by the Mn $d$-states. The apparent linear regime in $\sigma_1(\omega)$ observed in Mn$_3$Sn and Mn$_3$Ge arises from several overlapping interband transitions and therefore should not be interpreted as the optical signature of the Weyl cones. The optical response does not alter with
magnetic field up to 17 T, consistent with strong free-carrier screening. Our findings establish a comprehensive-correlated picture of Mn$_3$Sn and Mn$_3$Ge that offers a template for other correlated topological metals.
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All authors R. Mathew Roy, Bo Tai, Maxim Wenzel, Achyut Tiwari, Mykhaylo Ozerov, Chandra Shekhar, Claudia Felser, Artem V. Pronin, Xiaolong Feng, Martin Dressel
Soft Condensed Matter
Transport of Deformable Vesicles Driven by Chiral Active Brownian Particles
Dipak Patra and Anil Kumar Dasanna
Active matter systems can generate mechanical stresses that deform their surroundings, providing a route to transport and shape dynamics far from
equilibrium. Deformable vesicles containing active particles offer a minimal setting in which such active stresses are directly coupled to boundary mechanics. Here, we use numerical simulations to investigate a two-dimensional, fixed-area vesicle filled with chiral active particles interacting through excluded volume and polar
alignment. We find that the coupling between particle chirality and vesicle deformation produces distinct modes of collective motion, including run-and-tumble-like migration, rotor-like dynamics, and persistent spinning. Most notably, we show that vesicle rotation is non-monotonic in chirality: at fixed activity, an optimal chirality maximizes the rotational velocity. We develop an analytical theory that relates the vesicle rotation to the effective torque generated by the chiral active particles. The theory identifies the competition underlying the optimal chirality and predicts a scale-invariant dependence of the rotational velocity on activity and chirality. This scaling collapses simulation results obtained over different activity strengths onto a universal curve. Our results establish a general mechanism by which chirality and collective
alignment regulate the transmission of active stresses to deformable boundaries, providing a framework for understanding transport and rotational dynamics in confined active systems.
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Statistical Mechanics
Exact Nonlinear Active Microrheology in Diffusive Single-File Systems
Aurélien Grabsch and Olivier Bénichou
Active microrheology probes a crowded medium by forcing a tracer and measuring its response. In single-file transport, where particles cannot overtake, a constant force $F$ produces a subballistic displacement $\langle X_t\rangle\simeq \sqrt{t}\,\xi(F)$ together with a persistent bath deformation. Despite decades of work, the exact nonlinear response at arbitrary force has remained confined to a few special solvable models. Here we remove this restriction by combining recent advances in hydrodynamic transport coefficients, a pressure-balance formulation of the local drive, and single-file duality, which eliminates the resulting moving boundary. This yields a closed exact boundary-value problem for general diffusive single files, determining both $\xi(F)$ and the full density profile. For overdamped Brownian particles with general interactions, all microscopic interaction details enter only through the
equilibrium equation of state, bringing realistic interacting systems, including finite-width quasi-one-dimensional channels, within exact reach. The solution also reveals universal global laws; in particular, the bath-density dipole is fixed by the applied force independently of the interaction potential.
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Strongly Correlated Electrons · Cross-listed from quant-ph
Thermal entanglement on a frustrated tetrahedron: Probing quantum resources through concurrence and stabilizer structure
Reza Pourkhodabakhshi, Francis Dominie, Deep Gajera et al. (+1 more)
In a frustrated
spin system, highly entangled eigenstates can form a separable thermal mixture. We study this distinction for four
spin-$1/2$ moments on a tetrahedron, the elementary unit of the pyrochlore
lattice, with the general four-parameter exchange
Hamiltonian. Tetrahedral
symmetry allows a restricted search over thermal-state decompositions to be carried out by linear optimization, yielding an upper bound on multipartite concurrence and explicit separable decompositions where this bound vanishes. At low temperature, the concurrence maps show extended separable regions near the all-in–all-out limit, whereas suppression near the
spin-ice point is narrowly localized. Heating broadens the latter region as nearby multiplets are repopulated. The optimization identifies fully separable thermal states even when the eigenstate-averaged concurrence remains large. Negativity independently confirms finite-temperature
entanglement in selected coupling regions. A mixed-state stabilizer Rényi diagnostic, used to explore
quantum magic, favours different couplings and can increase locally with temperature. These results connect thermal
entanglement to the splitting and population of
symmetry multiplets, and provide a practical basis for identifying frustrated
spin configurations for studies of
quantum resources beyond the ground-state limit.
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All authors Reza Pourkhodabakhshi, Francis Dominie, Deep Gajera, Stephanie H. Curnoe
Strongly Correlated Electrons · Cross-listed from quant-ph
Universal entanglement embezzlement and divergent nonlocal magic from generic local chaotic quantum evolution
Matias Karjula, Teemu Ojanen, Kim Pöyhönen et al. (+2 more)
We show that, starting from a product state, local
unitary quantum evolutions generate intermediate states which exhibit a multiscale
entanglement-spectrum structure required for universal
entanglement embezzlement. This facilitates
entanglement extraction from a catalyst many-body state while leaving it asymptotically unchanged. Remarkably, these atypical structures emerge generically at intermediate stages, well before reaching maximum
entropy where thermalization has flattened out the spectral hierarchy. The resulting state is accompanied by nonlocal nonstabilizerness that diverges with the system size, consistent with a recently established equivalence between universal embezzlement and divergent nonlocal magic. Thus, without any fine tuning, a chaotic
quantum evolution generates intermediate states which form a universal family of catalytic reservoirs.
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All authors Matias Karjula, Teemu Ojanen, Kim Pöyhönen, Tapio Ala-Nissila, Moein N. Ivaki
Materials Science
Adaptive Substrate Support Based on Thin-Film Piezoelectric Actuators
Ertuğ Şimşek, Bas Jansen, Marcelo Ackermann et al. (+1 more)
Advanced lithography scanners require extreme substrate flatness in the range of nanometers to prevent focus errors. Such a flatness is challenging to reach and maintain using static substrate supports. Active correction concepts using bulk piezoelectric or linear actuators become prohibitive due to wiring and volume limitations, considering the thousands of pillars required. In this work, we present to our knowledge the first ever demonstration of an active substrate support concept based on thin-film piezoelectric actuators. The working principle, fabrication steps, and characterization of a proof-of-principle device, supported by finite element modeling (FEM), are presented in detail. The fabricated device shows a displacement above 9 nm, which is sufficient to correct some of the focus errors in lithography systems. We foresee that this new concept may open the way towards smaller chip dimensions and improved yield.
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All authors Ertuğ Şimşek, Bas Jansen, Marcelo Ackermann, Muharrem Bayraktar
Materials Science
Low Temperature Halide Assisted HVPE Growth of Single Crystal AlN Films
K. Udwary, M. Smeaton, J.S. Mangum et al. (+6 more)
Low defect, single polarity aluminum nitride layers grown by halide vapor phase epitaxy (HVPE) methods have classically needed growth temperatures well exceeding 1100{\deg}C with many of the best results being grown in the range of 1400{\deg}C. These high temperatures have typically been required to obtain Al-polar AlN films with smooth morphologies and high crystalline quality. However, these elevated temperatures make the use of quartz reactor chambers difficult, as quartz begins to soften at 1200{\deg}C, and requires specially designed reactors. This study examines the use of anhydrous hydrogen chloride (HCl) gas, injected directly to the growth surface, to suppress inverted polarity grains that form at low growth temperatures. This method allows for high quality, single
crystal AlN layers with a growth temperature of just 1000{\deg}C in a quartz reactor chamber. With this method, AlN layers of 5 um thickness were grown on c-plane (0 0 0 1) sapphire, with a growth rate of 20 um/hour, and a resulting full-width at half-maximum (FWHM) of symmetric (0 0 0 2) rocking curve reflection under 400 arcsec and asymmetric (1 0 -1 2) reflection under 1000 arcsec. Electron backscatter diffraction measurements showed the suppression of inversion domains with increasing free HCl, resulting in smoother and higher quality films.
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All authors K. Udwary, M. Smeaton, J.S. Mangum, R. Gannon, G. Dodson, B. Tellekamp, K.L. Schulte, J.H. Leach, J. Simon
Strongly Correlated Electrons
Orbital-Induced Peierls Transitions: How Orbitals Orchestrate Lattice Instability
T. Mizokawa and S.V. Streltsov
The Peierls transition is typically regarded as a phenomenon inherent to one-dimensional (1D) materials. However, orbital degrees of freedom can induce this instability even in higher dimensions. Two mechanisms are primarily responsible. First, the anisotropic shape of $p$ and $d$ orbitals can lead to effective "1D-zation" of the electronic spectrum. Second, orbital degrees of freedom can lift band degeneracy by shifting bands relative to each other via the local or band Jahn-Teller effect, thereby affecting the nesting of the Fermi surface. The orbital-induced Peierls effect is most commonly observed when ligand octahedra surrounding transition metals share edges, and less frequently in face-sharing geometries. In this review, we discuss the underlying physical mechanisms, the materials in which this phenomenon occurs, the characteristics of the high-temperature undistorted phase, and the role of local effects such as the formation of molecular orbitals.
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Materials Science
Hypothesis-Driven Autonomous Materials Synthesis with Multimodal LLM Agents
Izumi Takahara, Kazunori Nishio, Akira Aiba et al. (+4 more)
Self-driving laboratories can explore synthesis conditions autonomously, but their decision-making layer is typically a black-box optimizer, and the output is a set of optimized samples, with the measurements reduced to predefined scalar objectives and the reasons behind success left unarticulated. Here we present SynAgent, a framework in which large
language model
agents operate an automated experimental system and maintain an explicit, revisable understanding of the synthesis process as the campaign's primary output. Starting with no predefined analysis pipeline, SynAgent adaptively generates analysis skills for newly acquired data and evolves this understanding through
multimodal reasoning over experimental data such as X-ray diffraction patterns and electron micrographs. The
evolution is guided by a verify-falsify scheme, in which the
agent deliberately challenges its own hypotheses by testing conditions predicted to fail as well as those predicted to succeed. In a single campaign of 18 autonomous experiments using LiCoO2 (001) thin-film deposition as a testbed, SynAgent synthesized highly crystalline films and evolved an understanding of how the substrate temperature governs crystallization, discovering an abrupt threshold and a narrow optimal growth window at 650-690 {\deg}C. These results extend autonomous experimentation beyond optimized samples to testable, human-readable understanding.
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All authors Izumi Takahara, Kazunori Nishio, Akira Aiba, Shigeru Kobayashi, Takao Nakajima, Taro Hitosugi, Teruyasu Mizoguchi
Strongly Correlated Electrons
Optical investigation of the electronic structure of a ferromagnetic Weyl semimetal CeAlSi
Shin-ichi Kimura, Yue Pan, Hiroshi Watanabe et al. (+3 more)
To investigate electronic states during the ferromagnetic transition in a
magnetic Weyl semimetal CeAlSi, we measured temperature-dependent optical conductivity [$\sigma_1(\omega)$] spectra and compared them with DFT+DMFT band calculations. The $\sigma_1(\omega)$ spectrum did not change significantly across the ferromagnetic ordering temperature ($T_C$), suggesting that the Ce 4f states are almost localized. DFT+DMFT calculations with almost localized Ce 4f states successfully reproduced the spectral shape and the unchanged $\sigma_1(\omega)$ spectra across $T_C$. The dynamic effective mass evaluated from the extended Drude model is very small, which DFT+DMFT calculations also reproduce, but the scattering probability at even lower temperatures suggests ferromagnetic fluctuations. These results suggest that the interaction intensity between the Weyl
fermions and Ce 4f states is very weak, as reproduced by DFT+DMFT calculations.
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All authors Shin-ichi Kimura, Yue Pan, Hiroshi Watanabe, Akimitsu Kirikoshi, Junya Otsuki, Hiroshi Tanida
Materials Science
Nonempirical Time-Dependent Density Functional Theory Framework for Nonlocal Exchange–Correlation Potentials
Zhandos A. Moldabekov, Michele Pavanello, Thomas D. Gawne et al. (+2 more)
Advanced, orbital-dependent exchange–correlation (XC) functionals can significantly improve the description of electronic structural properties, but they substantially worsen spectral properties that are computed within standard linear-response time-dependent density functional theory frameworks. This is not a failure of the underlying Kohn-Sham states, but due to a formal inconsistency in the treatment of the dynamic density response when the non-locality of the XC potential is not taken into account consistently on the level of the full off-diagonal density
matrix. To avoid these complexities, we present a non-empirical additive correction $\Delta f_\textnormal{xc}(\mathbf{q},\omega)$ to the dynamic XC kernel that re-enforces the exact f-sum rule of the non-local KS
Hamiltonian within TDDFT. Comparing our new results against a representative set of accurate experimental measurements (ambient aluminum, silicon and carbon, as well as heated and compressed aluminum) reveals a dramatic improvement in all cases without any additional computational cost. The corresponding extension to the open-source GPAW code is made freely available online. We further investigate the implications of non-local pseudopotentials and show that the non-locality has an important, physically motivated effect that is indispensable to capture the correct plasmon dispersion in lieu of full all-electron simulations. In addition to being important for the estimation of a plethora of dynamic and spectral properties, our work constitutes an important step towards a universal XC functional that can be used to estimate all kinds of observables with high accuracy. Finally, we outline the potential utility of our framework for the development of advanced non-local XC functionals, and suggest a new way to rigorously verify non-local pseudopotentials against experimental measurements of collective excitations.
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All authors Zhandos A. Moldabekov, Michele Pavanello, Thomas D. Gawne, Jan Vorberger, Tobias Dornheim
Materials Science
ERAF4XRD: A multimodal agentic framework for constructing validated experimental X-ray diffraction databases from scientific literature
Afnan Mostafa, William Ratcliff, Simon J. L. Billinge et al. (+1 more)
The scientific literature contains decades of experimental measurements that remain difficult to access as structured data for modern AI and data-driven research. Much of this information is distributed across figures, captions, text, and tables, requiring experimental data and their context to be identified, connected, and verified before they can be reused. Here we introduce ERAF4XRD (Experiment Reader Agentic Framework for X-Ray Diffraction), a fully automated
multimodal (i.e., image and text), multi-
agent framework that reconstructs validated X-ray diffraction (XRD) records from scientific publications. ERAF4XRD downloads and screens documents, identifies XRD figures, extracts and links metadata to the corresponding experimental data, and validates outputs against source evidence using an independent validation
agent. On a manually curated
benchmark of 273 scientific publications containing 3,150 candidate figures, ERAF4XRD achieved up to 98.7% accuracy for XRD figure identification and generated 1,400 metadata values across 22 fields. Independent manual assessment of the final validated records yielded 98.5% precision and 90.7% recall, with no unsupported metadata observed among 443 evaluated fields. By moving beyond information extraction to the reconstruction and validation of linked experimental records, ERAF4XRD establishes an automated approach for transforming published scientific information into machine-readable experimental
datasets for AI and data-driven science.
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All authors Afnan Mostafa, William Ratcliff, Simon J. L. Billinge, Niaz Abdolrahim
Materials Science
Thermally Desorbable InN Capping Layers for Nitride Surface Science
Mellie Lemon, Amitayush Thakur, Anthony Rice et al. (+5 more)
Group III-nitride thin films are essential for optoelectronic and power devices, where surface and interface quality critically influence performance. It is often necessary to transfer these films through atmosphere for processing or characterization steps, which can introduce significant surface contamination. Here we demonstrate a technique to protect the surface of III-N films during atmospheric exposure by capping with sacrificial InN layers. Using molecular beam epitaxy grown AlGaN films as our representative protected material, we take advantage of the lower decomposition and desorption temperatures of InN and metallic In to remove the protective cap layer in situ via thermal desorption without damaging the AlGaN film beneath. Angle-resolved photoemission spectroscopy (ARPES) measurements of the valence band dispersion in Al0.4Ga0.6N demonstrate that the film surface is recovered after InN decapping, highlighting the versatility of this process in allowing further surface-sensitive characterization of films that had been exposed to air.
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All authors Mellie Lemon, Amitayush Thakur, Anthony Rice, Glenn Teeter, Michelle Smeaton, Renae Gannon, Jessica L. McChesney, M. Brooks Tellekamp
Mesoscale and Nanoscale Physics
Layer-Dependent Vibrational and Optical Properties of $\mathrm{Mo}{0.58}\mathrm{W}{0.42}\mathrm{Se}_2$ Alloy
Szymon Socha, Tomasz Wozniak, Elena Blundo et al. (+7 more)
Semiconducting Mo$_x$W$_{1-x}$Se$_2$
alloys provide a versatile platform for tailoring the optical properties of two-dimensional materials through both composition and layer thickness. Here, we systematically investigate mechanically exfoliated Mo$_{0.58}$W$_{0.42}$Se$_2$ flakes ranging from monolayer (1L) to nine layers by combining Raman scattering (RS), photoluminescence (PL), reflectance contrast (RC) spectroscopy, and first-principles
phonon calculations. Thirteen RS peaks are identified, including the low-frequency interlayer shear mode, whose thickness dependence is well described by a linear-chain model, yielding an interlayer force constant of $K_s=(2.996\pm0.015)\times10^{19}$ N m$^{-3}$. PL measurements reveal a crossover from the direct-bandgap 1L to indirect-bandgap multilayers. The thickness
evolution of the indirect optical transition is quantitatively reproduced using a
quantum-confinement model, yielding an out-of-plane reduced effective mass of $\mu_\perp=0.75 m_0$. RC spectroscopy reveals four excitonic resonances. While the A and B
excitons associated with the $K^\pm$ valleys remain nearly independent of layer thickness, the higher-energy C and D resonances originating from the band-nesting regions exhibit pronounced
redshifts, reflecting substantial thickness-induced modifications of the electronic band structure. These results establish comprehensive spectroscopic fingerprints of flake thickness, interlayer coupling, and electronic structure in Mo$_x$W$_{1-x}$Se$_2$
alloys and provide a reliable, non-destructive framework for their optical characterization.
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All authors Szymon Socha, Tomasz Wozniak, Elena Blundo, Malgorzata Brzoska, Grzegorz Krasucki, Piotr Wrobel, Antonio Polimeni, Adam Babinski, Maciej R. Molas, Katarzyna Olkowska-Pucko
Strongly Correlated Electrons · Cross-listed from hep-th
Deep learning emergent spacetime from fermionic spectral functions in holography
Koji Hashimoto, Hyun-Sik Jeong, Keun-Young Kim et al. (+2 more)
We present a physics-informed machine learning framework based on Neural Ordinary Differential Equations that solves the holographic inverse problem: reconstructing the bulk spacetime and gauge field of a charged AdS black hole directly from boundary fermionic spectral functions. Encoding the UV asymptotics, horizon regularity, and zero temperature extremality as hard constraints in the neural network architecture, our framework reliably reconstructs the extremal Reissner-Nordström AdS geometry across three
quantum critical regimes set by the $U(1)$ probe charge—non-Fermi
liquid, marginal Fermi
liquid (strange metal), and Fermi-
liquid-like states—and can jointly infer the probe charge itself to sub-percent accuracy. Relaxing the near-AdS boundary constraint uncovers a geometrical degeneracy: bulk profiles that differ throughout the radial direction but share the same near-horizon $AdS_2 \times \mathbb{R}^2$ data reproduce identical spectral functions near the Fermi surface. This isospectral non-uniqueness is precisely the bulk degeneracy expected on general holographic grounds at zero temperature, and its spontaneous emergence across independent training runs shows that the network isolates the IR CFT universality rather than overfitting a single UV completion.
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All authors Koji Hashimoto, Hyun-Sik Jeong, Keun-Young Kim, Daichi Takeda, Kwan Yun
Soft Condensed Matter
Conformational landscape of a macrocycle from REST enhanced sampling
Valentin Kasper, Nicole Holzmann, Sanjoy Ray et al. (+2 more)
We use replica-exchange molecular dynamics (REMD) to map the conformational free-energy landscape of the macrocyclic drug lorlatinib in explicit water and chloroform. In water a single dominant basin is recovered; in chloroform two conformational states are resolved. We use these conformers as the starting point to calculate
proton chemical shifts from first principles and a continuum solvent model. The resulting population-weighted spectrum is compared directly to the experimental CDCl$_3$ spectrum, benchmarking the computational approach against measured NMR data.
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All authors Valentin Kasper, Nicole Holzmann, Sanjoy Ray, Matthias Kaiser, Alons Lends
Mesoscale and Nanoscale Physics
Chiral classical and quantum acoustics with hole-spin qubits
Zhanning Wang, Yongtao Li, Nelson E. Rivas et al. (+5 more)
Gate-defined hole
spins combine strong
spin-orbit coupling with exceptional strain sensitivity, making surface acoustic waves a natural route to remote, phase-coherent control. We show that counterpropagating surface acoustic waves can differ in coupling strength and in whether they predominantly drive
spin rotations or modulate the
qubit frequency. We call the transverse transition-strength imbalance
spin-acoustic chirality and show that it is tunable through gate-controlled reshaping of the dot confinement. Combining a multiband Luttinger-Kohn
Hamiltonian with the Bir-Pikus description of strain and 3D piezoelectric finite-element simulations, we obtain the acoustic g-
matrix modulation governing coherent SAW driving. Quantizing the same strain-mediated interaction yields the corresponding single-
phonon coupling, and a generalized anisotropic Rabi interaction with co-rotating, counter-rotating, and longitudinal components, linking classical chirality to
quantum anisotropy and directional one-
phonon emission.
Magnetic field orientation and dot shape tune the acoustic chirality and operator selectivity. We illustrate this framework through bichromatic coherence protection and
phonon-mediated heralded Bell-state initialization.
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All authors Zhanning Wang, Yongtao Li, Nelson E. Rivas, Gonzalo García, Irene Castro, Rubén Seoane Souto, Daniel Ramos, José C. Abadillo-Uriel
Statistical Mechanics · Cross-listed from quant-ph
Lindbladian quantum chaos beyond classical strange attractors
Ángel L. Corps and Armando Relaño
We investigate the connection between classical and
quantum chaos in a dissipative system of two coupled collective
spins. Although the classical dynamics possesses a stable fixed-point attractor, we find pronounced signatures of chaos in the transient dynamics preceding relaxation. In the
quantum model, such transient chaos is accompanied by a transition to random-
matrix statistics in the relevant part of the Liouvillian spectrum and by a qualitative increase in the number of Liouvillian modes contributing to expectation values of physical observables. The transition occurs before the bifurcation at which the stable fixed point disappears and a chaotic attractor emerges. Our results show that Liouvillian
quantum chaos can be associated with transient classical chaos, rather than requiring a chaotic asymptotic attractor, and provide a refinement of the Grobe-Haake-Sommers
conjecture.
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Materials Science
A Pseudoscalar Representation Mapping from Parent-Group Vibrational Normal Modes to Symmetry-Adapted Magnetic Structures
Yachao Liu, Haibo Niu and Vei Wang
Conventional approaches classify
symmetry-allowed
magnetic configurations but do not by themselves establish a direct, mode-resolved correspondence with parent-
lattice vibrations. Here, we formulate a universal determinant-induced pseudoscalar twist for all 32 crystallographic point groups, establishing an exact representation-to-geometry correspondence between parent vibrations and
magnetic order. Within the paramagnetic gray group $G\times\Theta_{\mathcal{T}}$, the spatial twist determines
symmetry-defined
magnetic geometry, while time-reversal parity independently specifies
magnetic character. Each parent
phonon irrep $\Gamma$ maps to $\Gamma_{\mathrm{mag}}=\Gamma\otimes\Gamma_{\mathrm{ps}}$, preserving multiplicities and yielding the projection identity $P_{\mathrm{mag},mn}^{(\Gamma\otimes\Gamma_{\mathrm{ps}})}=P_{\mathrm{ph},mn}^{(\Gamma)}$ under the common Cartesian realization. This establishes the Template Principle: parent vibrational modes furnish real-space templates whose
symmetry-enforced nodal
manifolds are inherited exactly. Applied to monolayer $\mathrm{Cd}_2\mathrm{N}_3$, the framework identifies the ferrimagnetic ground state from the parent $A_{2u}$ sector, confirmed by first-principles calculations, alongside cluster
magnetic octupoles and antiferromagnetic
manifolds. It further provides an a priori parent-group criterion for screening
symmetry-allowed linear
magnetic responses.
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Materials Science
The role of disconnections in redox-induced phase transformation of metal oxides
Martina Ruffino, Baptiste Bienvenu, Xuyang Zhou et al. (+2 more)
Detailed atomic-level understanding of the phase transformation between magnetite (${\rm Fe_3 O_4}$) and haematite (${\rm Fe_2 O_3}$) is lacking, despite widespread interest in redox reactions of metal oxide systems. While the magnetite-to-haematite transformation entails the addition of oxygen to the system and thus a net diffusive flux, haematite formations have been reported to grow along well-defined habits on the close-packed $\{0001\}_{\rm Fe_2 O_3}//\{111\}_{\rm Fe_3 O_4}$ planes. The propagation of the phase interface in the bulk is thus thought to maintain the oxygen sublattice fixed up to a shear, and to require long-range
diffusion of iron ions. In this letter we propose interfacial steps with dislocation character, i.e. disconnections, as the elementary defects propagating the transformation. We use the topological model of interfacial defects to predict three disconnection modes for the system, and we employ scanning transmission electron microscopy to ascertain their presence in a haematite/magnetite interface of a partially oxidised magnetite powder. Using atomistic simulations, we determine the
equilibrium structures of the disconnections, and study their motion and how they accomplish the transformation, obtaining excellent agreement with atomic-resolution experimental observations.
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All authors Martina Ruffino, Baptiste Bienvenu, Xuyang Zhou, Dierk Raabe, Yan Ma
Materials Science
Rapid Parameter Estimation from Photoluminescence Decays of Halide Perovskite Thin Films
Robin Heumann, Toby Rudolph, Gaosheng Huang et al. (+2 more)
Extracting material parameters from experimental data is often challenging if no invertible analytical equation can be used to link the data with the quantities of interest. If the link between experiment and material parameters is given mathematically by a set of non-linear differential equations, these must be solved repeatedly during the traditional fitting procedure, resulting in long optimization times and limited insight into parameter uncertainty. Here, we present a parameter estimation workflow specifically aimed at transient photoluminescence measurements performed on lead-halide perovskite films. This workflow is accelerated using artificial neural networks for rapid comparison between experiment and simulation. An advantage of the method is the ability to rapidly scan multidimensional material parameter spaces and identify correlations between parameters that provide insights into the physics of non-radiative recombination in halide perovskites. Finally, we compare steady-state and transient photoluminescence and show how uncertainty in parameters such as the defect density can be reduced by including steady-state data in the parameter estimation workflow.
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All authors Robin Heumann, Toby Rudolph, Gaosheng Huang, Thomas Kirchartz, Chris Dreessen
Statistical Mechanics · Cross-listed from quant-ph
Measuring correlations in quantum and statistical systems
V.I. Yukalov and E.P. Yukalova
The survey discusses the problem of measuring correlations in composite
quantum and statistical systems. After briefly recalling the standard methods of describing correlations, the emphasis is on the method of correlation indices. The latter method for quantifying the strength of correlations in composite physical systems is sufficiently general allowing for measuring in a unique way the correlation strength in both
quantum and statistical systems, for static as well as for dynamic processes. The correlation indices, can be defined for correlation operators, reduced density
matrices, and other operators containing information on correlations in the studied composite systems. The correlation indices measure all types of correlations,
quantum correlations, such as
entanglement, as well as classical correlations. They are applicable for characterizing static as well as dynamical processes. Examples are given of correlation indices for several
quantum states and for
spin and pseudospin systems. The quantification of correlations in a nonequilibrium system is exemplified by calculating the correlation index for a trapped Bose-Einstein condensate subject to the action of an alternating field.
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Mesoscale and Nanoscale Physics
Fröhlich Bipolarons in Two-Dimensional Materials
A. Kudlis, V. Shahnazaryan, I. Iorsh et al. (+2 more)
Motivated by the progress in the physics of two-dimensional materials and the recent two-dimensional generalization of the Fröhlich model, we study the formation of bipolarons in polar monolayers. Because of very special nonlocal dielectric screening in two dimensions, this setting differs qualitatively from the conventional Fröhlich model. In monolayers, (i) long wavelength LO
phonons acquire a nontrivial dispersion; (ii) the Fröhlich electron-
phonon vertex becomes momentum-dependent and regular at small momenta; and (iii) direct repulsion between charge carriers takes the Keldysh-Rytova form. Using the Feynman path-integral variational approach, we show that the region in the parameter space where stable bipolarons exist is strongly modified compared to the usual quasi-two-dimensional model with dispersionless
phonons. Specifically, in the most favorable limit, when the ratio $\sigma_0$ of the static polarizability to the high-frequency polarizability tends to infinity, the lower critical coupling, sufficient for the formation of bipolarons, can be made arbitrarily small. More surprisingly, we demonstrate that no stable bipolarons can exist in the strong coupling limit: in the isolated monolayer the stability region is always confined to a finite range of coupling constants. In general, the stability region is strongly shifted toward large values of the polarizability ratio $\sigma_0$, well beyond the parameter regimes in representative
crystals, which indicates that polar monolayers do not favor bipolarons.
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All authors A. Kudlis, V. Shahnazaryan, I. Iorsh, I. A. Shelykh, I. V. Tokatly
Mesoscale and Nanoscale Physics
Altermagnetic Magnons in Dipolar Nanomagnet Arrays
Rhea Hoyer, Ephraim Spindler, Lukas Körber et al. (+3 more)
Altermagnetism is conventionally understood in a
spin-conserving framework, where
symmetry-enforced momentum-dependent
spin splitting emerges in collinear magnets with vanishing net magnetization. Here, we show that its defining signatures persist in nanomagnet arrays coupled exclusively by dipolar interactions, despite the intrinsic breaking of
spin conservation. Using a macrospin theory of dipolar-coupled ferromagnetic nanoislands, corroborated by micromagnetic simulations, we demonstrate that arrays engineered with altermagnetic
symmetries exhibit
spin-split
magnon bands whose eigenstates can partially remain strongly
spin polarized. The resulting
spin expectation value displays the characteristic $d$-wave pattern throughout the Brillouin zone, establishing a mesoscopic realization of altermagnetic
magnons beyond the conventional
spin-conserving paradigm. As a consequence,
spin-wave propagation becomes strongly direction dependent, providing a highly tunable platform for anisotropic
magnon transport and synthetic altermagnetic functionality.
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All authors Rhea Hoyer, Ephraim Spindler, Lukas Körber, Tobias Wagner, Mathias Weiler, Alexander Mook
Quantum Gases
Geometry-Driven Suppression of Fermionic Pairing on a Spherical Surface
Lorenzo Frigato, Andrea Tononi and Luca Salasnich
We investigate the ground-state properties of a two-component attractive Fermi gas confined to a spherical surface, demonstrating how
curvature and finite-size effects lead to qualitatively different behavior compared to the planar limit. In the strongly attractive regime, the system forms a Bose-Einstein condensate (BEC) of tightly bound dimers, yielding a gap and chemical potential that approach flat-space results with leading-order
geometric corrections. However, as the attraction decreases, the system crosses over into a Bardeen-Cooper-Schrieffer (BCS) regime where the Cooper pair size becomes constrained by the sphere radius, producing pronounced deviations from flat-space behavior. We identify strong shell effects at magic particle numbers set by the single-particle spectrum, revealing the geometry-driven suppression of fermionic pairing at weak interactions. Our results highlight a fundamental interplay among geometry,
quantum statistics, and interactions, motivating future experiments with shell-trapped ultracold
fermions and inspiring geometry-controlled condensed matter devices.
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