Materials Science · Cross-listed from cond-mat.str-el
Deviation from Fermi-liquid $T^2$ resistivity caused by collective transport
Kamran Behnia
`Fermi-
liquid behavior' is nowadays used as a shorthand for quadratic temperature dependence of the electrical resistivity. In a metal, for this to occur, electrons must be cooled well below the Fermi degeneracy temperature, $T_{\mathrm{F}}$. A departure from this behavior is observed at finite temperature. Here, we note that this departure has opposite signs in two distinct types of Fermi
liquids. In weakly correlated ones, the upward departure implies a higher exponent of the inelastic resistivity, attributable to additional scattering by
phonons. In contrast, there is a downward deviation in strongly correlated metals, which implies either reduced scattering or additional conduction, as in the case of normal
liquid $^3$He, in which a distinct contribution to heat transport by a sound mode has been recently identified. Such a channel of conduction smoothly transforms across $T_{\mathrm{F}}$ to the one captured by the Bridgman formula for thermal conductivity of classical
liquids. In three metals (UPt$_3$, Sr$_2$RuO$_4$, and heavily overdoped LSCO), according to the available experimental data, the normalized amplitude of excess conductivity at $T/T_{\mathrm{F}}\simeq0.02$ is comparable to what has been seen in $^3$He, suggesting, without establishing, a common origin.
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Materials Science
Plasmon drag and photoinduced magnetic effects in plasmonic and magnetic metals
Md Afzalur Rab, Terence Baker and Natalia Noginova
Photoinduced electric effects in plasmonic and
magnetic materials under pulsed
laser illumination exceed the prediction of the electromagnetic momentum-transfer mechanism by orders of magnitude. In order to get more information on the nature of the effect we study the kinetics of photovoltages in permalloy thin films at different photoexcitation configurations. The photoinduced electric signals consist of magnetically dependent and magnetically independent components which are of significant magnitude and mainly follow the temporal profile of the
laser pulse. In contrast, the predicted contribution from the Anomalous Nernst Effect is much weaker and exhibits substantially slower kinetics. These observations suggest that ultrafast photoexcited hot electrons, rather than thermal mechanisms, play the dominant role in generating the observed photovoltage.
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Materials Science
FP-DeErr: Application-Oriented Error Decomposition for Foundation Potentials
Kiyan Amirian, Ramanuja Srinivasan Saravanan, Felix Adams et al. (+2 more)
Foundation potentials (FPs) have emerged as a new basis for atomistic modeling. While their evaluation using average energy and force errors often indicates near-DFT accuracy, their performance in practical computational studies remains inconsistent. While recent
benchmarks evaluate FPs on downstream computational tasks, the underlying errors that determine task success or failure are not always clear. Here, we develop FP-DeErr, an application-oriented error-decomposition framework that resolves FP errors according to the physically meaningful quantities, configurations, and computational stages governing specific tasks. Rather than averaging errors over an entire
dataset, FP-DeErr uses decomposed error metrics devised for physically meaningful quantities, focusing on the configurations where errors arise and matter most. We demonstrate FP-DeErr by evaluating multiple state-of-the-art FPs on three fundamental tasks: force prediction for atomistic simulations, energy ranking for substitutional and vacancy orderings, and ion/vacancy migration. These error-decomposition metrics resolve force errors among highly accurate, large-error, and far-from-
equilibrium atoms; relative-energy errors among competing orderings, phases, and compositions; and ion migration errors among endpoints and along-path errors. By identifying where FP errors arise, this error decomposition provides targeted guidance for FP development. FP-DeErr also provides an open
benchmark, evaluation code, and a public leaderboard for rigorous FP assessment.
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All authors Kiyan Amirian, Ramanuja Srinivasan Saravanan, Felix Adams, Charles E Schwarz, Yifei Mo
Materials Science
Bridging simulation length scales with cellular automata
John J. Karnes, Esteban D. Gadea, Shakkira Erimban et al. (+2 more)
Multiscale simulation requires coupling physics models that operate at different characteristic length and time scales, because no single method spans the range needed for most problems of interest. Moving to a coarser-grained representation unlocks longer length and time scales, but it discards the microscopic interactions that build morphology. A fine-grained model can be initialized from an arbitrary packing and left to self-assemble into a physically meaningful structure; a lower-resolution model cannot, and must inherit its starting configuration from a higher-fidelity simulation. The length scales accessible to the coarse-grained model are therefore set not by the coarse-grained method itself, but by the largest fine-grained configuration that can be affordably equilibrated. A representative example is the scale-up from particle-based molecular dynamics (MD) to a
lattice-based representation such as kinetic Monte Carlo (kMC). In this work, we present a cellular automata (CA) approach for generating arbitrarily large
lattice starting configurations. CA is a natural fit for this task: short-ranged local rules drive the
evolution of a
lattice, and their repeated application gives rise to emergent long-range order, thematically mirroring how short-ranged interactions in MD produce self-assembled morphology. We use a configuration from a higher-fidelity simulation as a training set and learn the CA rules from it via logistic regression. As a proof of principle, we develop these rules for a hydrated anion exchange membrane (AEM), generate new starting configurations, and
benchmark their performance in mesoscale kMC simulations against an MD-derived "ground truth." We then demonstrate the ability to generate substantially larger
lattices and show that their behavior in kMC is consistent with that of the smaller CA
benchmark configurations.
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All authors John J. Karnes, Esteban D. Gadea, Shakkira Erimban, Ignacio J. Bombau, Valeria Molinero
Materials Science · Cross-listed from physics.chem-ph
Differentiable Solvation Shell Model for Rational Electrolyte Design
Hancheng Zhao, Hongyi Lin, Celia Kelly et al. (+1 more)
Tailoring Li+ solvation structures has emerged as a promising design principle across multiple Li metal battery (LMB) electrolytes, with localized high concentration electrolytes (LHCE) emerging as a leading candidate. However, rational design of these electrolytes remains limited by a poor quantitative understanding of how molecular properties govern Li+ solvation shell composition. Here we introduce a mean field modeling framework, built on an Ising model, that predicts solvation shell composition from donor number (DN), acceptor number (AN), molar ratio, and molecular size. This framework is end-to-end differentiable, which enables parameterization directly from molecular dynamics (MD) solvation structures via gradient-based optimization. Focusing on LHCE, the model achieves 10.7% RMSE and R2=0.87 for shell composition, 2.3% RMSE on free solvent ratio, and further reproduces solvation trends in real LHCE electrolytes, at a fraction of MD's cost. Our model also shows good generalizability on other electrolyte systems in addition to LHCE. Analysis of its interaction terms shows that DN dominates Li+ solvation energetics, providing a thermodynamic basis for empirical DN-based design rules. We further demonstrate the model's design utility on the LiTFSI/tetraglyme (G4) system absent from training. The model identifies fluorobenzene (FB) as a promising diluent and predicts a salt-concentration window with anion-rich solvation shells and low free solvent, favorable for stable anion-derived SEIs and high oxidative stability, respectively. This prediction is validated by higher-fidelity MD. This work establishes an interpretable differentiable framework for predicting Li+ solvation shell composition, with potential to extend to other electrolyte classes.
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All authors Hancheng Zhao, Hongyi Lin, Celia Kelly, Venkatasubramanian Viswanathan
Materials Science · Cross-listed from cs.AI
The convergent laboratory: when AI reasoning, autonomous experiments, high performance and quantum computing reshape chemistry
Eliu Huerta, Xiaoyun Wang, Geetika Gupta et al. (+7 more)
This Comment emerges from TPC26 (https://tpc26.org), a conference convening leaders from academia, national laboratories, and industry who are reshaping materials science discovery. The meeting explored how AI, autonomous
agents, self-driving labs, higher performance and
quantum computing converge to amplify their individual impact on materials science discovery. The perspectives here reflect the firsthand experiences of researchers at these frontiers and capture the essence of this global endeavor. As AI-driven
reasoning, autonomous agentic frameworks, self-driving laboratories, and fault-tolerant
quantum processors mature simultaneously, we offer this Comment as a reference at what we believe is a tipping point of transformative advances and productive disruption in the chemical sciences.
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All authors Eliu Huerta, Xiaoyun Wang, Geetika Gupta, Edward H. Sargent, Cameron J. Owen, Victor Fung, Abhishek Mitra, Austin Cheng, Emma Bouchard, Shams Mehdi
Materials Science · Cross-listed from cond-mat.mes-hall
First principles calculations of electric-field-driven topological phase transitions in silicene, germanene and stanene
Julián Antonio Villarreal Murúa, Pablo Roura-Bas, Javier Daniel Fuhr et al. (+1 more)
The emergence of two-dimensional topological materials, particularly the group-14 monolayers known as silicene, germanene, and stanene has opened promising pathways for next-generation nanoelectronics and spintronics. Their buckled honeycomb structure and strong
spin-orbit coupling allow for bandgap engineering via a perpendicular electric field, leading to topological phase transitions (TPTs) from non-trivial to trivial insulating states. However, precise determination of the critical electric field $E_z^{\text{cr}}$ at which these transitions occur remains challenging, with tight-binding models often underestimating these values. Here, we present a first-principles framework that combines density-functional theory (DFT), maximally localized Wannier functions, and
evolution of the Wannier charge centers (WCC) to accurately characterize TPTs in silicene, germanene, and stanene through the $\mathbb{Z}_2$ topological invariant. In contrast to earlier work, at each electric-field strength we run fully self-consistent ab initio simulations to obtain the screened electronic structure, accounting for the material's dielectric response from both electrons and ions. From these converged results we construct a Wannier tight-binding
Hamiltonian at each electric field strength, which then enables a gauge-invariant calculation of the $\mathbb{Z}_2$ topological invariant. This methodology yields significantly more accurate numerical predictions of $E_z^{\text{cr}}$, $0.020$ and $0.250$ V/Å for silicene and germanene, respectively. Compared to previous approaches, our framework delivers a marked quantitative improvement for predicting topological phase boundaries, essential for guiding the design of topological field-effect transistors and electrostatically controlled
quantum devices based on two-dimensional materials.
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All authors Julián Antonio Villarreal Murúa, Pablo Roura-Bas, Javier Daniel Fuhr, Ricardo Faccio
Materials Science
From Electronic Structure to Environmental Remediation: Adsorption of Ionized Glyphosate on COOH-Modified Carbon Nanotube
H. T. Silva, L. C. S. Faria, C. Aguiar et al. (+2 more)
Glyphosate is a widely used herbicide whose persistence and toxicity in aquatic and terrestrial environments demand efficient removal strategies. Here we employ GFN2 xTB calculations with implicit ALPB aqueous solvation and automated docking to investigate the adsorption of all five pH dependent ionized forms of glyphosate (G1-G5) on (10,0) single walled carbon nanotubes covalently functionalized with carboxyl groups at 0-25% coverage. Adsorption energies reveal a clear charge dependent trend: the dianionic (G4) and trianionic (G5) species exhibit the most negative binding energies over the entire functionalization range, while the protonated and neutral forms (G1, G2) bind weakly, approaching reversible adsorption at high COOH contents. The deprotonated form G5 strengthens from -2.17 eV on pristine CNT to about -5.7 eV at 10% and 25% functionalization, with a local minimum near 15-20% COOH due to steric and electrostatic crowding of adjacent groups. Decomposition of the solvation free energy shows dominant electrostatic stabilization complemented by increasingly favorable hydrogen bond contributions as carboxyl density grows. All complexes display very small HOMO-LUMO gaps (0.02-0.22 eV), indicating high electronic sensitivity to adsorption and functionalization. Overall, CNT+COOH systems can operate in both strong capture and regenerable regimes depending on glyphosate ionization state, offering a tunable platform for pH responsive remediation.
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All authors H. T. Silva, L. C. S. Faria, C. Aguiar, T. A. Aversi-Ferreira, I. Camps
Materials Science
Customized spin spirals in ferromagnetic thin films
Anjali Panchwanee, Kai Schlage, Dieter Lott et al. (+8 more)
The advancement of spintronic nanoscale devices hinges on the ability to flexibly engineer
magnetic spin structures in thin-film stacks with precision and control. Meeting this demand remains a challenge for stable non-collinear
spin configurations and, more specifically, vertical
spin spirals in thin films. Innovative methods are required for their fabrication, stabilization and control. Here, we use oblique-incidence deposition to design and stabilize vertical
spin spirals at room temperature and without an external field in
magnetic thin films. We induce two crossed uniaxial
magnetic anisotropies at the thin film boundaries. These anisotropies are tunable in direction and strength, thus providing control over the angular range and depth profile of the resulting
spin spiral. The combination of polarized
neutron reflectometry and nuclear resonant scattering enables precise and direct determination of the depth-dependent
spin configurations. Our results establish a single-film design approach, in which the surface anisotropies independently serve as controllable design parameters for tailoring the vertical
spin-spiral profile. Potential applications include nanoscale energy-storage devices,
magnetic sensors, and ferromagnetic-resonance filters, advancing all-
spin-based device engineering in general.
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All authors Anjali Panchwanee, Kai Schlage, Dieter Lott, Sven Velten, Thomas Saerbeck, David L. Cortie, Sakshath Sadashivaiah, Ilya Sergeev, Guido Meier, Lars Bocklage, Ralf Röhlsberger
Materials Science
Remote epitaxy beyond polarity
Ching-Tai Fu, Pei-Jan Hung, Xudong Li et al. (+21 more)
Remote epitaxy through a monolayer two-dimensional material-covered substrate establishes a crystallographic registry across the van der Waals (vdW) surface that enables the epitaxial growth, lift-off and transfer of single-crystalline films. A central belief in remote epitaxy is that the substrate facilitating the phenomenon must be a material with strong ionicity, as the interatomic electrostatic potential fluctuation in covalent and metallic materials is substantially attenuated by two-dimensional materials. Here, we show remote epitaxy is possible when the substrate is a metallic or covalently bonded material and experimentally demonstrate non-polar remote homo- and heteroepitaxy across a wide range of material systems, including both metals and
semiconductors. The achieved non-polar remote interactions are designed and engineered by harnessing substrate conductivity and vicinal surface step-edge density. These findings indicate that remote epitaxy is universal and applicable to ionic, metallic, and covalent materials, expanding its capabilities and stimulating a plethora of new fundamental scientific questions about the mechanism of remote epitaxy.
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All authors Ching-Tai Fu, Pei-Jan Hung, Xudong Li, Xiaolong Zhu, Yu Han, Sayantan Mahapatra, Zhiheng Zhao, Qingsong Fan, Xubing Wu, Qizhang Li, Chenxi Sui, Zirui Zhou, Ting-Hsuan Chen, Cheng-Hao Lei, Ivan Kuzmenko, Xiaobing Zuo, Byeongdu Lee, Alexander S. Filatov, Jeffrey R. Guest, Fengyuan Shi, Yuzi Liu, Hua Zhou, Yunfeng Shi, Po-Chun Hsu
Materials Science · Cross-listed from physics.app-ph
Thermoelectric properties of metal-semiconductor percolation composites
Oleksandr Porubaniyi, Sergii Tomko, Mihailo Cherkez et al. (+2 more)
We analyze thermoelectric response of composite materials comprising homogeneous
semiconductor hosts with randomly distributed metallic inclusions. We demonstrate that the properties of such materials are strongly affected by the percolation transition (with background conductivity). We show that in vicinity of percolation threshold, the power factor and the thermoelectric figure of merit strongly depend on both the concentration and arrangement of inclusions. Finally, we identify promising regimes for enhancing the power factor in realistic composites.
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All authors Oleksandr Porubaniyi, Sergii Tomko, Mihailo Cherkez, Viktor Podolskiy, Radion Cherkez
Materials Science · Cross-listed from cond-mat.supr-con
Ni-O hybridization as a stabilizer for $s^{\pm}$ superconductivity in La$_3$Ni$_2$O$_7$: a DFT+RPA study
Lauro B. Braz, Daniel D. Rivera, Emmanuel V. C. Lopes et al. (+3 more)
The superconducting gap
symmetry of high-pressure bilayer nickelates remains under debate, with weak- and strong-coupling approaches yielding different pairing tendencies. In this work, we investigate how the weak-coupling treatment of electronic states away from the Fermi level influences
magnetic fluctuations and superconductivity in La$_3$Ni$_2$O$_7$. We employ a full-spectrum model based on orthonormalized projections of Kohn-Sham states onto local Ni-$e_g$ orbitals, which preserves the density-functional band structure while redistributing spectral weight over a wide energy range. Compared to a low-energy description, this approach yields enhanced interlayer
spin fluctuations and a commensurate
magnetic instability. Within a
spin-fluctuation framework, these features favor a sign-changing $s^\pm$ superconducting state, whereas low-energy models tend to stabilize $d$-wave pairing. Our results suggest that interlayer coupling in full-energy models may play an important role in shaping the predicted pairing
symmetry of bilayer nickelates.
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All authors Lauro B. Braz, Daniel D. Rivera, Emmanuel V. C. Lopes, George B. Martins, Gustavo M. Dalpian, Luis G. G. V. Dias da Silva
Materials Science · Cross-listed from cond-mat.str-el
Dipolar and quadrupolar spin supersolid states in a spin-1 triangular antiferromagnet
Yixuan Huang, Yuan Gao, Wei Li et al. (+2 more)
We present a systematic numerical study of the
spin-1 antiferromagnetic Heisenberg model on the triangular
lattice in an out-of-plane
magnetic field, using Density
Matrix Renormalization Group (DMRG) methods. By mapping out the
quantum phase diagram as a function of the single-ion anisotropy $D_z$ and
magnetic field, we identify distinct dipolar and quadrupolar
spin supersolid states, characterized by spontaneous U(1)
symmetry breaking with finite
spin superfluid stiffness coexisting with longitudinal translational
symmetry breaking. At zero field, the dipolar
spin supersolid with a 'Y'-type
spin configuration persists down to $D_z = 0$, whereas the quadrupolar
spin supersolid prevails at large $D_z$. At intermediate fields, the phase diagram is dominated by an up-up-down phase. At high fields below saturation, a quadrupolar
spin superfluid emerges in the large-$D_z$ regime, whereas a dipolar
spin supersolid with a 'V'-type
spin configuration dominates at small $D_z$. These phases are characterized through their order parameters and
spin superfluid stiffness using calculations on various system sizes. Furthermore, the dynamical
spin structure factor is obtained across the phase diagram, where characteristic spectral signatures of different phases are observed, including the gapless Goldstone mode and the roton-like minima. These features are directly accessible to inelastic
neutron scattering experiments. Our results provide a theoretical understanding of the interplay between frustrations, anisotropy, and Zeeman interactions in driving distinct
spin supersolid phases in the
spin-1 system, which are relevant to various triangular-
lattice antiferromagnets such as Na$_2$BaNi(PO$_4$)$_2$ and K$_2$Ni(SeO$_3$)$_2$.
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All authors Yixuan Huang, Yuan Gao, Wei Li, Seiji Yunoki, Sadamichi Maekawa
Materials Science · Cross-listed from physics.app-ph
What Photocurrent Versus Effective Voltage Tells Us About Charge Generation in Organic Solar Cells
Ardalan Armin, Austin M. Kay, Drew B. Riley et al. (+2 more)
The photocurrent of an organic solar
cell is routinely plotted against an effective voltage and used to extract an
exciton dissociation probability, and through it a free-charge generation efficiency. The photocurrent measures neither. Using a drift-
diffusion model in which free-charge generation is field independent and losses occur only by bimolecular recombination, we show that the apparent dissociation probability returned by this procedure lies well below unity even for complete dissociation. Across wide variations of carrier mobility and recombination strength it is a single-valued function of the fill factor and coincides with the short-
circuit charge collection efficiency, reporting neither the generation yield nor anything about collection beyond what the fill factor already shows. Even for ideal transport the normalised photocurrent saturates below unity at an intensity-independent first-order limit set by recombination of photogenerated carriers with injected
equilibrium charge. Applied to four organic solar
cells whose generation efficiencies are known independently, the apparent dissociation probabilities track the short-
circuit collection efficiency rather than the generation yield. We therefore suggest this construction not be used, particularly in the high-efficiency non-fullerene acceptor systems that are now state of the art.
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All authors Ardalan Armin, Austin M. Kay, Drew B. Riley, Oskar J. Sandberg, Paul Meredith
Materials Science
Neural-field design of broadband Rayleigh-wave carpet cloaks under microstructure realisability constraints
David Aznaurov, Davit Piliposyan, Danila Rukhovich et al. (+1 more)
Transformation elasticity provides appropriate material distributions for elastodynamic cloaks but the required stiffness tensors generally violate the minor
symmetries of Cauchy elasticity and are difficult to realise using conventional materials. Existing approaches restore these
symmetries by modifying the transformed tensor, producing only an approximate cloak. In this work rather than modifying the transformed tensor we seek the best performing cloak within the class of Cauchy materials. We formulate 2D Rayleigh wave carpet cloak design as an optimisation problem governed by partial differential equations. Using a coordinate based neural-field and a differentiable finite element model solver we optimise symmetric stiffness and density fields by minimising wave field distortion. Both single frequency and broadband optimisation are considered, with the broadband model trained over multiple frequencies. Physical realisability is addressed using a database of homogenised microstructures through conditional
diffusion, neural-field inverse design, and nearest-neighbour selection. FEM simulations show that the optimised Cauchy design approaches the ideal transformation-based cloak. After projection onto explicit microstructures, the homogenised representation recovers approximately 97% of the defect free reference surface-displacement magnitude, while direct FEM simulation of the fully resolved microstructured geometry recovers approximately 76%
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All authors David Aznaurov, Davit Piliposyan, Danila Rukhovich, Sebastien Guenneau
Materials Science
Interfacial Accommodation as a Candidate Ductility Pathway in Intermetallic-Rich Alloys
Avik Mahata
Heterophase interfaces are increasingly recognized as active participants in plastic deformation, yet quantitative methods for comparing their strain-accommodation capacity remain limited. Here, we present an atomistic framework for quantifying interface-mediated strain accommodation using molecular dynamics simulations. Interface broadening, roughening, and migration are extracted from atomistic trajectories and combined into an Interface Accommodation Index, with a normalized counterpart accounting for differences in initial interface structure. A weighting sensitivity analysis demonstrates that the relative ranking of interfaces is robust to the specific form of the index. The framework is demonstrated for three experimentally motivated interfaces, Al/Al3Ti, Al/Al9M2, and Al9M2/Al3Ti (M = Fe, Co, Ni), under tensile, compressive, and shear loading. Bulk simulations show that Shockley partial dislocations dominate plastic deformation, with
alloy chemistry governing the transition toward mixed-character dislocation networks. Tensile loading produces the greatest interface accommodation, while shear produces comparatively limited structural
evolution. The Al9M2/Al3Ti interface exhibits both the highest yield resistance and the largest accommodation response, suggesting that intermetallic-intermetallic interfaces can simultaneously sustain load and redistribute strain. These simulations quantify structural accommodation rather than ductility or fracture directly; their connection to macroscopic ductility therefore requires experimental validation. The framework provides a transferable approach for comparing interface accommodation in multiphase
alloys and identifies interface chemistry and crystallography as important design variables for damage-tolerant structural materials.
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Materials Science
Semiclassical thermoelectric transport in disordered Dirac electron system Ag2Te
Kentaro Kuga, Keisuke Hirata, Daiki Goto et al. (+3 more)
We investigated the thermoelectric effects of the Dirac electron system Ag2Te under
magnetic field. Our anal-ysis based on the Boltzmann semiclassical model associated the disorder with the unconventional
magnetic field responses such as linear magnetoresistance, linear Nernst effect, step-like Nernst effect, and sign change in Nernst effect. The analysis also revealed the impurity band near the Fermi energy. We simultaneously clari-fied the serious impact of the thermal Hall effect on the measurement of the Nernst effect, and we proposed the definitive solution. Our careful measurement and analysis will be the standard for the thermoelectric study under
magnetic field.
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All authors Kentaro Kuga, Keisuke Hirata, Daiki Goto, Ryogo Ishihara, Masaharu Matsunami, Tsunehiro Takeuchi
Materials Science
Anharmonic Lattice Dynamics and Anisotropic Electron-Phonon Coupling in Quasi-1-Dimensional Charge Density Wave Ta2NiSe7
Prithwija Mandal, S. Nanthini, Aditya Singh et al. (+4 more)
The microscopic origin of charge density wave formation in quasi one dimensional Ta2NiSe7 remains actively debated, particularly regarding the relative contributions of Fermi surface nesting, electron
phonon coupling, and
lattice instabilities. Here, we combine temperature and orientation dependent polarized Raman spectroscopy with first principles calculations to uncover the anisotropic electronic and
lattice interactions governing the CDW state in Ta2NiSe7. Heat capacity and electrical transport measurements identify an incommensurate CDW transition at 61 K. Raman spectroscopy reveals pronounced in plane anisotropy, with e ph coupling strength along intrachain b axis exceeding five times that along interchain c axis, whereas
lattice anharmonicity is enhanced by threefold along c axis. First principles calculations identify Ta2 Se octahedral vibrations and Ta Se electronic states near the Fermi level as dominant channels mediating the anisotropic e ph interaction. Exceptionally strong and directional e ph coupling along b axis establishes
lattice driven electronic instability as the primary mechanism underlying CDW modulation and highlights the dominance of intrachain interactions in strongly coupled Ta2NiSe7. Despite this strong coupling, the CDW remains incommensurate, indicating that
lattice anharmonicity provides an additional degree of freedom. Enhanced anharmonicity along c axis suggests that anisotropic
phonon phonon interactions reshape the free energy landscape and contribute to stabilizing incommensurate phase. These findings reveal a cooperative interplay between anisotropic e ph coupling and
lattice anharmonicity in governing CDW formation in low dimensional
quantum materials.
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All authors Prithwija Mandal, S. Nanthini, Aditya Singh, Kewal S. Rana, Dibyendu Dey, Kanishka Biswas, Ajay Soni
Materials Science
Symmetry-protected triplet Weyl complexes
Yun-Yun Bai, Ke-Xin Pang, Yan Gao et al. (+2 more)
The Nielsen-Ninomiya
theorem dictates that Weyl nodes must appear in pairs of opposite chirality to preserve global charge neutrality. However, in
crystals, specific crystalline
symmetries can stabilize multi-Weyl nodes, circumventing this pairwise constraint and enabling compensated Weyl complexes with mixed chiral charges. The minimal configuration of this type is a triplet Weyl complex (TWC), comprising exactly three Weyl nodes. Here, we systematically investigate the
symmetry conditions required to realize TWCs. By screening all 1651
magnetic space groups (MSGs) in both spinless and spinful systems, we establish that: (i) Only TWCs with charge magnitudes of $\{1,1,2\}$ and $\{1,2,3\}$ are permitted; (ii) the $\{1,1,2\}$ configuration can be realized in 166 spinless MSGs and 70 spinful MSGs; and (iii) the $\{1,2,3\}$-TWCs, which has not been reported before, can occur in 10 MSGs for both spinless and spinful cases. We explicitly demonstrate the existence of $\{1,2,3\}$-TWC in a tight-binding model. Furthermore, we present the first electronic realization of $\{1,1,2\}$-TWC topological semimetal state in the chiral carbon allotrope DZQH-C$_{36}$, in which the three Weyl nodes form a collinear configuration, leading to a characteristic “S”-shaped surface Fermi arc pattern. Our findings uncover novel topological states featuring mixed chiral charges and provide guidance for exploring their physics in concrete material systems.
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All authors Yun-Yun Bai, Ke-Xin Pang, Yan Gao, Weikang Wu, Shengyuan A. Yang
Materials Science
Cross-Layer Anomalous Hall Transport driven by Néel-Vector rotating in the Altermagnet candidate V2Te2O
Yanan Pan, W. Z. Zhuo, Pan Gao et al. (+7 more)
In van der Waals (vdW) materials, weak interlayer coupling generally suppresses vertical dispersion, reinforcing the conventional paradigm that in-plane transport dominates over cross-layer channels. Here, using first-principles calculations and
magnetic symmetry analyses, we uncover a giant,
symmetry-unlocked cross-layer anomalous Hall conductivity (AHC) in the vdW altermagnet V2Te2O. In the
magnetic ground state with Neel vector N//z, horizontal mirror
symmetry protects a
spin-polarized nodal chain near the Fermi level and strictly enforces zero anomalous Hall response. Tilting the Neel vector explicitly breaks this mirror protection, allowing
spin-orbit coupling to gap the nodal chain and activate a sharp cross-layer Hall response. When the Neel vector is rotated into the in-plane configuration (N//x), cross-layer orbital hybridization generates intensive Berry
curvature hotspots, boosting the cross-layer component of AHC {\sigma}_{yz} to approximately 255 S/cm, which exceeds in-plane component {\sigma}_{xy} by nearly two orders of magnitude. Furthermore, varying the azimuthal angle systematically redistributes the anomalous Hall response, enabling full directional control of transverse transport. Our findings demonstrate a highly sensitive cross-layer anomalous Hall switch activated by low-barrier
spin canting, offering promising avenues for directional tensor selection and low-power multi-axial vdW spintronics.
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All authors Yanan Pan, W. Z. Zhuo, Pan Gao, Ziyu Zhou, Junqing Xu, Lijie Shao, Damin Meng, Weiwei Chen, Zhongjun Li, Ye Yang
Materials Science
A locally ab initio computational framework for arbitrary incommensurate materials interfaces
Drake Niedzielski and Tomás A. Arias
Incommensurate materials interfaces constitute a broad and technologically important class of systems, yet their lack of shared periodicity limits predictive and computationally efficient first-principles electronic-structure methods. Here we introduce a scalable computational framework for constructing locally ab initio electronic
Hamiltonians for arbitrary materials interfaces. Our approach exploits the nearsightedness of Wannier
Hamiltonian matrix elements, enabling their systematic extrapolation and interpolation across interlayer registries. This strategy yields transferable
Hamiltonians that retain first-principles accuracy while bypassing the need for prohibitively large commensurate supercells or Moiré approximations. We validate the framework on quasicrystalline 30{\deg} twisted bilayer
graphene, reproducing experimentally observed spectral features including mirrored Dirac cones and minigaps at avoided crossings arising from generalized interlayer scattering. We further predict quasiperiodic flat-band states in experimentally accessible doping regimes. By enabling predictive electronic-structure calculations across structurally incommensurate interfaces, this framework establishes a practical route to first-principles exploration of emergent interfacial phenomena.
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Materials Science
Generalized Helicity-Dependent Magnetization Switching via Substrate Phonons
F.G.N. Fennema, H. Damas, H. Yoshikawa et al. (+3 more)
Coherent excitation of circularly-polarized substrate
phonons can drive deterministic reversal of magnetization in an adjacent
magnetic layer. However, the extent to which this substrate-mediated mechanism can be generalized across different materials remains unresolved. Here, we measure and compare the spectral dependence of helicity-dependent magnetization reversal in
magnetic GdFeCo layers grown on a diverse set of diamagnetic substrates. Switching is observed for all investigated substrates, spanning six point groups and several infrared-active transverse-optical
phonon symmetries. While the switching spectra broadly overlap with the Reststrahlen bands, their maxima are systematically shifted to wavelengths shorter than the corresponding transverse-optical
phonon resonances. This spectral mismatch shows that substrate absorption alone does not determine the switching efficiency. Transfer-
matrix calculations show that strong absorption concentrates energy deposition near the substrate interface, providing a possible source of local heating that could suppress magnetization reversal. Our results reveal the broad applicability of substrate-mediated phononic switching while showing that its efficiency is governed by the full optical response of the
heterostructure rather than substrate absorption alone.
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All authors F.G.N. Fennema, H. Damas, H. Yoshikawa, A. Tsukamoto, C.S. Davies, A. Kirilyuk
Materials Science
Influence of dislocation density on the tribological response in oxides: case study on SrTiO3
Chukwudalu Okafor, Oliver Preuß, Thomas Chudoba et al. (+6 more)
Most ceramics suffer from brittle surface damage and cracking when small particles slide across the surface under low load. Microscratching tests are a useful technique to mimic this loading scenario while retaining the material's deformation history; however, the impact of pre-seeded dislocations, which can significantly facilitate plastic deformation, has not been explored in ceramics. Here, the influence of mechanically seeded dislocations on the microscratching response of oxides is investigated using a model perovskite, SrTiO3. First, various dislocation densities over four orders of magnitude are introduced via room-temperature cyclic Brinell indenter scratching. Subsequently, load-ramped microscratching tests are performed within the pristine and dislocation-seeded regions using a nominally 30 {\mu}m spherical diamond tip. On the reference pristine surface, we observe a clear transition from elastic to elasto-plastic deformation, followed by median/radial cracking at higher loads. In contrast, pre-seeded dislocations, accompanied by residual compressive stresses, suppress elastic deformation and lead to median/radial crack shortening and subsequent transition to a partial cone crack. The subsurface cracks are characterized by 3D Nano-CT. The changes in crack geometry, with and without dislocations, were described using the Lawn-Evans-Marshall and Lawn-Wiederhorn-Roberts models. These findings provide direct evidence of dislocation-regulated near-surface damage tolerance, with general applicability to other plastically deformable oxides.
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All authors Chukwudalu Okafor, Oliver Preuß, Thomas Chudoba, Ujjval Bansal, Daniela Exner, Konrad Priszokovich, Yanfei Gao, Christoph Kirchlechner, Xufei Fang
Materials Science
Local coordination, structural softening, and polarization-switching energetics in Sc-alloyed GaN
Shailesh Kalal, Gueorgui Kostov Gueorguiev, Martin Magnuson et al. (+8 more)
Sc-alloyed wurtzite nitrides exhibit strongly tunable electromechanical and ferroelectric properties, yet the relationship between their
lattice evolution and local bonding environment remains insufficiently established, particularly in Sc$_x$Ga$_{1-x}$N. Here, we investigate the structural and local bonding
evolution of Sc$_x$Ga$_{1-x}$N across the dilute-to-intermediate composition range by combining X-ray diffraction, Sc K-edge X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS) and first-principles calculations. Sc incorporation produces an anisotropic
lattice expansion and a progressive reduction in the c/a ratio. XANES and EXAFS reveal a concurrent modification of the local environment around Sc, with the effective Sc-N coordination number increasing from 4.1(4) to 4.5(2) and the average Sc-N bond length increasing from 2.045(7) to 2.081(8)Å over x=0.06-0.26. The local response is accompanied by a reduction in the Sc K-edge pre-edge intensity, consistent with a gradual reduction of the local tetrahedral asymmetry. First-principles calculations show that these structural changes are associated with site-selective distortions around Sc and progressive flattening of the structural energy landscape. The calculated intrinsic polarization-switching barrier decreases from 24.2 to 19.0 meV/Å$^3$ with increasing Sc content, while the calculated piezoelectric stress coefficient (e$_{33}$) increases from 0.82 to 1.66~C/m$^2$ and elastic constant (C$_{33}$) decreases from 380 to 227~GPa, resulting in an increase of piezoelectric strain coefficient (d$_{33}$) from 2.99 to 12.46~pC/N. These results show that Sc incorporation progressively modifies the local coordination environment and structural energetics of ScGaN while the long-range wurtzite structure remains preserved over the investigated composition range.
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All authors Shailesh Kalal, Gueorgui Kostov Gueorguiev, Martin Magnuson, Edward Ferraz de Almeida Junior, Rohini Sanikop, Sagar Jathar, Per Sandström, Ray-Hua Horng, Jens Birch, Per Eklund, Ching-Lien Hsiao
Materials Science · Cross-listed from physics.chem-ph
Operando imaging of intercalation memory in MXenes
Franz Groebmeyer, Mohsen Beladi, Christoph G. Gruber et al. (+6 more)
Ion intercalation enables reversible control of charge, structure and function in layered solids. Yet layered materials contain nanosheets with different thicknesses and stacking, whose intercalation pathways are averaged out in ensemble measurements. This becomes critical under Angstrom-scale confinement, where ion transport couples to solvent reorganization and host deformation, leaving the origins of kinetics, reversibility and activation unresolved. Here we combine operando interferometric scattering and interference reflection microscopy to resolve
proton-driven dynamics in individual single- and multilayer Ti3C2Tx MXene flakes and show that even a few stacked layers introduce a significant kinetic barrier. Cycling then separates nanosheets into three persistent behaviors: reversible monolayers, restacked multilayers with incomplete recovery and delayed deintercalation, and coherently stacked multilayers that self-stabilize through reversible folding. Operando synchrotron X-ray diffraction shows this
memory at electrode scale, where the interlayer structure converges towards a reproducible state. Our findings reveal cycling-induced structural
memory that governs subsequent intercalation in layered MXenes.
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All authors Franz Groebmeyer, Mohsen Beladi, Christoph G. Gruber, Ruocun Wang, Pol Salles, Nhu Quynh Nguyen, Jakub Drnec, Yury Gogotsi, Emiliano Cortes
Materials Science
Nuclear quantum effects in the thermal conductivity of solid hydrogen
Hengtai Zheng, Zezhu Zeng and David E. Manolopoulos
We use a combination of path integral and
lattice dynamics methods to calculate the thermal conductivity of solid parahydrogen. Path integral molecular dynamics is first used to calculate a centroid potential of mean force at each temperature, on which a harmonic
phonon basis is constructed using the finite displacement method. We then calculate anharmonic force constants on the centroid potential and solve the linearised
phonon Boltzmann transport equation for the thermal conductivity. The resulting renormalised
phonon dispersion curves, heat capacity, and thermal conductivity are all in remarkably good agreement with experimental measurements. We find that the heat transport is dominated by collective relaxon modes at low temperatures and cannot be captured by making the
phonon relaxation time approximation. Indeed, quantitative agreement with the experimental thermal conductivity is only achieved when the nuclear
quantum effects in the centroid potential of mean force,
phonon boundary scattering, and hydrodynamic transport are all explicitly considered. This is also likely to be the case for other
quantum crystals.
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