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Physics Condensed Matter Materials Science

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Saturday 4 April

Materials Science · Cross-listed from cond-mat.supr-con

Analytical evaluation of surface barrier and resistance in iron-based superconducting multilayers for Superconducting Radio-Frequency applications

Carlos Redondo Herrero and Akira Miyazaki

New superconducting materials, particularly iron-based superconductors (IBS), have recently attracted attention for their potential applications in particle detectors and accelerators. This paper discusses the application of these materials in multilayer structures for radio-frequency resonators used to accelerate charged particles, with the aim of improving performance compared to bulk niobium. These materials are compared with previously studied multilayers composed of conventional superconductors in terms of the maximum magnetic field they can withstand, their surface resistance, and their power loss per unit surface area. Finally, perspectives and future applications aimed at increasing operating temperatures are discussed.
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Materials Science

Thermal Hall resistivity and transverse entropy production in a phonon gas

Xiaodong Guo, Xiaokang Li, Alaska Subedi et al. (+2 more)

Most theories of the phonon thermal Hall effect ignore phonon-phonon interactions. Here, by recalling the Senftleben-Beenakker effect in molecular gases, we argue that a magnetic field, by influencing collisions between neutral non-chiral [quasi-]particles, can induce a Hall response. Our study of two insulators with distinct crystal structures, layered honeycomb WS$_2$ and ferroelectric perovskite LiNbO$_3$, finds that $\kappa_{xx}$ and $\kappa_{xy}$ peak at nearly the same temperature in both materials, as reported in other insulators. We show that the amplitude of transverse thermal resistivity in clean and simple insulators is of the order of $|W_\perp/B|\simeq \frac{e}{k_B u}$, where $e$ and $k_B$ are fundamental constants and $u$ is the binding energy density of the crystal. In complex and dirty insulators, $|W_\perp/B|$ is much larger and has a significant temperature dependence. Nevertheless, the peak thermal Hall angle in all insulators remains roughly the same.
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All authors Xiaodong Guo, Xiaokang Li, Alaska Subedi, Zengwei Zhu, Kamran Behnia

Materials Science · Cross-listed from cond-mat.str-el

Interface and Strain Control of Emergent Weyl Semimetallic Phase in SrNbO$_{3}$/LaFeO$_{3}$ Heterostructures

Sairam Ithineni, Pratik Sahu, Soumyakanta Panda et al. (+8 more)

Realizing correlated topological semimetallic phases in bulk transition-metal oxides remains challenging due to rigid lattice symmetry, correlation-induced gap opening, and limited structural tunability. However, complex-oxide thin films and heterostructures provide a powerful platform to stabilize topological phases by tailoring the requisite lattice symmetry through strain control and interface design. In this study, we demonstrate the emergence of Weyl-like electronic states and associated chiral transport in SrNbO$_3$ (SNO)/LaFeO$_3$ (LFO) bilayers. Transport measurements reveal signatures consistent with nontrivial topology, including large non-saturating MR, a nonlinear Hall response, and a chiral anomaly like feature in longitudinal magnetotransport under parallel electric and magnetic fields ($\mathbf{B} \parallel \mathbf{I}$). In addition, we observe a \textcolor{black}{signature} of anomalous Hall contribution, likely arising from \textcolor{black}{proximity effect induced by LFO layers at the interface}. First-principles calculations reveal an $a^0a^0c^-$ rotation pattern of the NbO$_6$ octahedra, together with interfacial lattice distortions in the SNO layer that drive the emergence of a twofold degenerate Weyl semimetallic phase protected by screw axis lattice symmetry. This is further confirmed by Berry curvature calculations, which show opposite sign Berry curvature peaks for the upper and lower band characteristic of a Weyl node. Our combined experimental and theoretical results highlight the critical role of strain and interfacial octahedral distortions in stabilizing Weyl phase in transition metal based perovskite bilayer.
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All authors Sairam Ithineni, Pratik Sahu, Soumyakanta Panda, Aditya Mehta, Debashree Nayak, Amit Chauhan, Shwetha G Bhat, Niharika Mohapatra, K. Senapati, B. R. K. Nanda, D. Samal

Materials Science · Cross-listed from cond-mat.soft

Potential energy landscape picture of zero-temperature avalanche criticality governing dynamics in supercooled liquids

Norihiro Oyama, Yusuke Hara, Takeshi Kawasaki et al. (+1 more)

Supercooled liquids are metastable states realized by suppressing crystallization below the melting temperature. While it is well established that their dynamics slow down dramatically and become spatially heterogeneous upon cooling, the microscopic origin of these nontrivial glassy phenomena remains a matter of active debate. In the present study, by means of molecular dynamics simulations, we first demonstrate that nontrivial slow dynamics, such as structural relaxation and dynamical heterogeneity, can be consistently described within a zero-temperature avalanche criticality picture. Since this finding suggests that the potential energy landscape plays a crucial role in determining the dynamics, we further quantify the potential energy landscape from three distinct perspectives. Based on these analyses, we propose a potential-energy-landscape picture of avalanche criticality that is consistent with various previous studies. Our proposed picture explains in a unified manner previously unexplained observations near the mode-coupling transition, such as the saturation of the dynamical susceptibility and the localization of unstable modes in saddle configurations.
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All authors Norihiro Oyama, Yusuke Hara, Takeshi Kawasaki, Kang Kim

Materials Science

First-principles theory of spin magnetic multipole moments in antiferromagnets

Hua Chen, Guang-Yu Guo and Di Xiao

Antiferromagnets with vanishing net magnetization are naturally expected to host higher-order magnetic multipole moments. Understanding and utilizing the multipole degrees of freedom are imperative for novel conceptual designs and applications unique to antiferromagnets. However, a universal, quantitative definition of magnetic multipole moments of antiferromagnetic materials is currently lacking. In this work we provide a unified description of arbitrary-order spin magnetic multipole moments (SM$^3$) of antiferromagnets by introducing a nonlocal spin density in macroscopic Maxwell equations. The formalism makes it transparent how SM$^3$ calculated for translationally invariant bulk systems corresponds to experimental observables when translation symmetry is broken. Through the nonlocal spin density calculated from first principles, we propose a robust scheme to extract arbitrary-order SM$^3$ through symmetry-constrained fitting at long wavelengths. Using this approach, we have calculated SM$^3$ of a few representative antiferromagnets, including $\alpha$-$\rm Fe_2O_3$, Mn$_3$Sn, and Mn$_3$NiN. Moreover, we clarify the role of spin-orbit coupling (SOC) in SM$^3$, especially in the weak SOC limit where clean predictions can be made based on symmetry principles. Our work paves the way for systematically investigating multipolar order parameters of unconventional magnetic materials.
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Materials Science · Cross-listed from cond-mat.soft

Zero-temperature Avalanche Criticality Governing Dynamical Heterogeneity in Supercooled Liquids

Norihiro Oyama, Yusuke Hara, Takeshi Kawasaki et al. (+1 more)

In supercooled liquids, mesoscale mobile and immobile domains are ubiquitously observed, a phenomenon known as dynamical heterogeneity. Extensive studies have established that the characteristic size of these domains grows upon cooling and exhibits system-size dependence. However, the physical origin of this domain growth remains a matter of active debate. In this work, using molecular simulations, we demonstrate that the temperature and system-size dependence of dynamical heterogeneity can be explained within a zero-temperature avalanche criticality picture.
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All authors Norihiro Oyama, Yusuke Hara, Takeshi Kawasaki, Kang Kim

Materials Science

KappaFormer: Physics-aware Transformer for lattice thermal conductivity via cross-domain transfer learning

Mengfan Wu, Junfu Tan, Yu Zhu et al. (+1 more)

Machine learning has been widely used for predicting material properties. However, efficient prediction of lattice thermal conductivity ($\kappa_\mathrm{L}$) remains a long-standing challenge, primarily due to the scarcity of high-quality training data. Here we introduce KappaFormer, a physics-aware Transformer architecture that embeds the harmonic-anharmonic decomposition of $\kappa_\mathrm{L}$ within the network. KappaFormer comprises a harmonic branch pre-trained on large-scale elastic property data and an anharmonic branch fine-tuned on limited experimental $\kappa_\mathrm{L}$ data, enabling effective knowledge transfer and enhanced generalization. High-throughput screening with KappaFormer identifies multiple candidates with ultralow $\kappa_\mathrm{L}$, which are further confirmed by first-principles calculations. Physics interpretability further elucidates the vibrational mechanisms governing thermal transport suppression, linking structural motifs to strong anharmonicity. This study provides a generalizable framework for physics-guided machine learning to accelerate the discovery of new materials.
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All authors Mengfan Wu, Junfu Tan, Yu Zhu, Jie Ren

Materials Science

Design A Family of 2D Nb-Based Multilayer Kagome Semimetals with High Fermi Velocity and Low Thermal Conductivity

En-Qi Bao, Xing-Yu Wang, Su-Yang Shen et al. (+3 more)

Although two-dimensional (2D) multilayer kagome materials have opened up new windows of opportunity for exploring novel physical properties, their development has been constrained by the scarcity of available material systems. In light of this, in this study, relying on our previously proposed innovative "1+3" design strategy for multilayer kagome materials, we have successfully designed nine stable 2D niobium-based multilayer kagome monolayers with tunable compositions: Nb<sub>6</sub>Cl<sub>2</sub>S<sub>3</sub>Br<sub>6</sub>, Nb<sub>6</sub>Cl<sub>2</sub>S<sub>4</sub>Br<sub>6</sub>, Nb<sub>6</sub>Cl<sub>2</sub>Se<sub>3</sub>Br<sub>6</sub>, Nb<sub>6</sub>Cl<sub>2</sub>Se<sub>4</sub>Br<sub>6</sub>, Nb<sub>6</sub>Cl<sub>2</sub>S<sub>1</sub>Se<sub>3</sub>Br<sub>6</sub>, Nb<sub>6</sub>Cl<sub>2</sub>S<sub>3</sub>Se<sub>1</sub>Br<sub>6</sub>, Nb<sub>6</sub>S<sub>4</sub>Cl<sub>8</sub>, Nb<sub>6</sub>Se<sub>4</sub>Br<sub>8</sub>, and Nb<sub>6</sub>Br<sub>2</sub>S<sub>3</sub>Se<sub>1</sub>Cl<sub>6</sub>. These nine new materials all belong to the category of Dirac semimetals, with their Dirac cone structures primarily arising from the dz<sup>2</sup> orbitals based on Nb-based kagome lattice. Hybrid functional calculations reveal that these materials boast Fermi velocities as high as 2.36-3.04*10<sup>5</sup> m/s. Moreover, these materials generally exhibit characteristics of relatively low phonon group velocities and shorted phonon lifetimes. Under room temperature conditions, they possess comparatively low lattice thermal conductivities, with values ranging from 1.704-8.149 Wm<sup>-1</sup>K<sup>-1</sup> . Our research not only robustly confirms the feasibility of the "1+3" multilayer kagome lattices design strategy in the realm of kagome material development but also sets an exemplary benchmark for the study of Nb-based multilayer kagome materials.
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All authors En-Qi Bao, Xing-Yu Wang, Su-Yang Shen, Jun-Hui Yuan, Wen-Yu Fang, Jiafu Wang

Friday 3 April

Materials Science

Microwave-to-optical transduction using magnon-exciton coupling in a layered antiferromagnet

Pratap Chandra Adak, Iris McDaniel, Suvodeep Paul et al. (+12 more)

Coherent interfaces between microwave-frequency quantum systems and low-loss optical links are essential for quantum networks. However, existing microwave-optical transducers often trade conversion efficiency against added noise, bandwidth, and device integrability. Here, we demonstrate coherent microwave-to-optical transduction based on magnon-exciton coupling in the layered antiferromagnet CrSBr. Driving the antiferromagnetic resonance with microwave signals imprints coherent modulation on a reflected optical probe, generating optical sidebands that are resonantly enhanced near excitonic transitions. While prior magnon-based approaches to microwave-to-optical transduction have typically relied on intrinsically weak off-resonant magneto-optical effects (e.g., Faraday rotation), our scheme exploits strong light-matter interactions at exciton resonances. Even in a bulk crystal without cavity enhancement, we observe coherent conversion over an intrinsically broadband window of ~ 300 MHz. We further show that multiple exciton-polariton resonances inherit the magnon-coupled response, suggesting a route to broaden the usable optical detuning range and to mitigate optical dissipation. Our results establish magnon-coupled excitons in layered magnets as a scalable platform for broadband microwave-optical interfaces, with pathways to higher cooperativity via reduced magnetic volume and cavity integration.
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All authors Pratap Chandra Adak, Iris McDaniel, Suvodeep Paul, Caleb Heuvel-Horwitz, Bikash Das, Vitali Kozlov, Kseniia Mosina, Arun Ramanathan, Xavier Roy, Zdeněk Sofer, Tian Zhong, Akashdeep Kamra, Arno Thielens, Andrea Alù, Vinod M. Menon

Materials Science · Cross-listed from cond-mat.soft

Anatomy of a Complex Crystallization Pathway

Charlotte Shiqi Zhao, Domagoj Fijan and Sharon C. Glotzer

Using molecular dynamics simulations, we investigate the crystallization pathways of two exemplary systems that form the same complex crystal structure but differ fundamentally in the nature of their particle interactions. One system is composed of point particles interacting via an isotropic pair potential characteristic of metallic compounds, while the other system contains hard polyhedra whose interactions arise from emergent entropic forces. Despite the stark difference in the origins of the particle interactions, we find that both systems are polymorphic and share the same crystal polymorphs. Moreover, the two systems follow the same multistep crystallization pathways, and by examining the complex crystallization pathways on the single particle level, we find that the local structure evolution of the two systems is also similar. By mapping the hard particle system's interaction to an effective pairwise potential, we find that such resemblance arises from the particle interactions being effectively similar.
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Materials Science · Cross-listed from cond-mat.supr-con

Enhanced Kadowaki-Woods Ratio and Weak-Coupling Superconductivity in Noncentrosymmetric YPt$_2$Si$_2$ Single Crystals

Gustavo Gomes Vasques, Shyam Sundar, Deisy Aristizábal-Giraldo et al. (+6 more)

Superconductivity in noncentrosymmetric RPt2Si2 (R = rare earth) compounds exhibit a rich playground to explore the competition between different ground states, such as unconventional superconductivity, antiferromagnetism and charge density wave. Here, we report the successful single crystal synthesis of noncentrosymmetric YPt2Si2 superconductor, with a transition temperature Tc = 1.67 K, via Sn flux method. The high quality of the prepared single crystals was confirmed using powder and Laue XRD measurements. The superconducting and normal state properties are investigated using electrical transport and heat capacity measurements down to 0.5 K. In the normal state, unlike LaPt2Si2, no charge density wave transition is observed in YPt2Si2, as evidenced by electrical transport and specific heat measurements. A relatively large Kadowaki-Woods ratio and a linear temperature variation of the electrical resistivity in an extended temperature range of 50-300 K suggest an unconventional normal-state in YPt2Si2. The estimated superconducting parameters indicate that YPt2Si2 is a type-II superconductor with weak electron-phonon coupling. The temperature dependence of specific heat in the superconducting state can be explained reasonably well using an isotropic two-gap model. A positive curvature near Tc in the temperature variation of upper critical field also supports the two-gap superconductivity. First-principles DFT calculations suggest a BCS-like superconducting state driven primarily by d-electron contributions. The calculated electron-phonon coupling constant identifies the material as a weak-coupling superconductor, with the McMillan-Allen-Dynes formula yielding a Tc of 1.8 K. Additionally, we provide a comparative analysis of the superconducting and normal-state properties of YPt2Si2 and compositionally similar LaPt2Si2.
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All authors Gustavo Gomes Vasques, Shyam Sundar, Deisy Aristizábal-Giraldo, Juan F. Castello-Arango, Rafael Sá de Freitas, Adriano Reinaldo Viçoto Benvenho, Takahiro Onimaru, Jorge M. Osorio-Guillén, Marcos A. Avila

Materials Science

Observation of anomalous thermal Hall effect in altermagnets

Wenbo Wan, Xu Zhang, Yixuan Luo et al. (+2 more)

Altermagnets, recently proposed as a third category of collinear magnets, combine the features of zero net magnetization in antiferromagnets and the spin splitting in ferromagnets. While abundant spectroscopic evidence for altermagnetism has been reported, experimental observation of the anomalous Hall effect, a hallmark of ferromagnetism, remains scarce. Here, we shift the paradigm from charge to heat carriers and report the systematic study of the thermal Hall effect in two representative altermagnet candidates, MnTe and CrSb. In both materials, we observe a pronounced anomalous phonon thermal Hall signal, with no electrical counterpart observed, attributed to the coupling of this distinctive magnetic structure with phonons. Our findings establish the anomalous phonon thermal Hall effect as an intrinsic feature of altermagnets, and provide a sensitive probe to identify this new kind of quantum magnets. The anomalous phonon thermal Hall effect in altermagnets directly links the Néel vector to lattice vibrations, opening prospects for low-loss phononic devices and thermally readable memories.
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All authors Wenbo Wan, Xu Zhang, Yixuan Luo, Yanfeng Guo, Shiyan Li

Materials Science

Maximizing the magnetic anisotropy of Dy complexes by fine tuning organic ligands: A systematic multireference high-throughput exploration of over 30k molecules

Lion Frangoulis, Lorenzo A. Mariano. Vu Ha Anh Nguyen, Zahra Khatibi et al. (+1 more)

The design of the coordination environment of magnetic ions is key to achieving properties such as large magnetic anisotropy and slow magnetic relaxation, but a systematic exploration of the relevant chemical space for these compounds is missing. Here, we automatically extract all entries of mononuclear Dy coordination complexes from crystallographic databases and use multireference ab initio methods to compute their magnetic anisotropy. In addition, we generate and simulate magnetic anisotropy for 25k new molecules with the general formula [Dy(H$_2$O)$_5$L$_2$]$^{n-}$ and pentagonal bipyramidal coordination geometry, a motif selected as very promising. While no molecule with record magnetic anisotropy is serendipitously identified in crystallography databases, molecules with crystal field splittings over 1600 cm$^{-1}$ are identified by systematically exploring new organic ligands. This corresponds to a ~100% increase of magnetic anisotropy over the reference compound, ~30% over any known pentagonal bipyramidal Dy complex, and approaching record values of pseudo bi-coordinated Dy ions. This study demonstrates that the fine-tuning of Dy's second coordination sphere by organic ligands design can significantly improve magnetic anisotropy and that automated computational screening is key to accelerating this chemically non-intuitive process.
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All authors Lion Frangoulis, Lorenzo A. Mariano. Vu Ha Anh Nguyen, Zahra Khatibi, Alessandro Lunghi

Materials Science · Cross-listed from physics.chem-ph

Regio-Connectivity and Torsional Angle Effects on Singlet Fission and SOCT-ISC in Aza-BODIPY Dimers

Sophiya Goyal and S. Rajagopala Reddy

Aza-BODIPY dimers represent promising molecular systems for efficient triplet-state generation through either intramolecular-singlet fission (iSF) or spin-orbit charge transfer intersystem crossing (SOCT-ISC). In this work, we investigate the role of molecular geometry in governing these mechanisms across four regioisomeric aza-BODIPY dimers (D[1,1], D[1,3], D[3,3], and D[2,2]) using multireference quantum-chemical calculations. Ground- and excited-state properties were analyzed at the MP2 and SA-XMCQDPT levels of theory, while diabatic couplings and spin-orbit matrix elements were evaluated to estimate iSF and SOCT-ISC rate constants, respectively. Our results reveal that triplet formation is strongly governed by the torsional angle ({\Phi}) between monomer units, with regio-connectivity exerting a secondary influence. Dimers D[1,1] and D[1,3] exhibit favorable iSF energetics and coupling magnitudes, whereas D[2,2] displays low iSF rate constant (kSF ) but enhanced SOCT-ISC activity. The D[3,3] dimer shows exothermic multiexciton formation but reduced iSF efficiency due to destructive coupling interactions. The dominant ISC channel proceeds through the S1-T3 transition with large spin-orbit coupling and a small energy gap. These findings provide critical mechanistic insights into geometry-dependent triplet generation in aza-BODIPY dimers.
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Materials Science

Spatially inhomogeneous delithiation in LiNiO2 positive electrode: the effect of X-rays dose

Francesco La Porta, Laurent Barthe, Anthony Beauvois et al. (+4 more)

Operando synchrotron X-ray techniques have become essential tools for investigating rechargeable batteries as they provide real-time insights into electrochemical processes. However, the high brilliance of synchrotron radiation can alter the electrochemical mechanisms within the battery, thereby compromising the reliability and reproducibility of operando measurements. In this study, we introduce a novel methodology that directly correlates the local X-ray dose with the Ni4+/Ni3+ redox activity in a LiNiO2 positive electrode. Full-field transmission X-ray absorption spectroscopy imaging (FFI-XAS) is employed to probe the charge-compensation mechanism during lithium extraction at the micrometre scale, using two beam configurations with different focal distances (far-focus and near-focus). While the spatially averaged XAS spectra exhibit sluggish reaction, regions exposed to lower dose rates exhibit the expected electrochemical evolution. This contrast enables the identification of a dose threshold for reliable operando measurements. This approach establishes a practical dose limit and provides spatially resolved insight into beam-induced effects, offering both a diagnostic framework and a pathway toward more reliable operando experiments.
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All authors Francesco La Porta, Laurent Barthe, Anthony Beauvois, Gilles Wittmann, Valérie Briois, Antonella Iadecola, Stéphanie Belin

Materials Science

Engineering Electrochromism in Ni-Deficient NiO through Defect, Dopant, and Strain Coupling

Katarina Jakovljević, Ana S. Dobrota, Igor A. Pašti et al. (+1 more)

The electrochromic response of Ni-deficient NiO is governed by vacancy-mediated electronic processes that can be strongly influenced by dopant chemistry and lattice deformation. Using density functional theory, we systematically investigated Cu-, Sn-, and V-doped Ni-deficient NiO(001) surfaces and examined alkali-ion insertion at surface Ni vacancies. Li insertion proceeds as nearly complete ionic electron donation (~+0.9 e), but the fate of the injected electron depends on dopant identity. V-doping preserves framework-dominated charge compensation and leads to conventional bleaching through filling of vacancy-associated hole states. In contrast, Sn actively traps the injected charge, generating dopant-assisted optical transitions and reversing the electrochromic response, while Cu produces an intermediate spectral redistribution without significant dopant reduction. Substitution of Li by Na or K in the V-doped system does not alter the switching mechanism, confirming that vacancy-state filling governs the optical behavior. Biaxial tensile strain enhances the energetics of Li insertion but reduces optical contrast by altering the defect electronic structure. These results establish dopant activity, vacancy stabilization, and lattice strain as key parameters controlling electrochromism in NiO-based materials.
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All authors Katarina Jakovljević, Ana S. Dobrota, Igor A. Pašti, Natalia V. Skorodumova

Materials Science · Cross-listed from cond-mat.str-el

Microscopic NMR evidence for successive antiferroelectric and antiferromagnetic order in the van der Waals magnet CuCrP$_2$S$_6$

C. S. Saramgi, L. F. Prager, S. Selter et al. (+5 more)

We present a comprehensive $^{31}$P and $^{65}$Cu nuclear magnetic resonance (NMR) study of the layered van der Waals magnet CuCrP$_2$S$_6$. The compound exhibits a sequence of structural and magnetic phase transitions: a high-temperature paraelectric state, followed by a quasi-antiferroelectric (QAFE) state near 185 K, a long-range antiferroelectric (AFE) phase below 150 K, and finally, antiferromagnetic (AFM) order below $T_\mathrm{N}$ = 30 K. The evolution of the NMR spectra, NMR shift, and spin-lattice ($T_1^{-1}$) and spin-spin ($T_2^{-1}$) relaxation rates provide direct microscopic fingerprints of these transitions. The splitting of both the NMR line and $T_1^{-1}$ below the AFE transition demonstrates the emergence of two inequivalent P sites. From $K - \chi$ analysis, we extract nearly isotropic transferred hyperfine couplings and show that the NMR shift anisotropy originates primarily from the dipolar contribution, in contrast to Mn$_2$P$_2$S$_6$ and Ni$_2$P$_2$S$_6$. We determine the ferromagnetic intralayer exchange $J_{intra}\approx$ -4.9 K from the Curie Weiss temperature, consistent with ferromagnetic layers antiferromagnetically stacked along the $c$ axis, and evaluate the Moriya high temperature relaxation rate including cross correlation effects of the P P dimer. Critical divergence of $T_1^{-1}$ near $T_\mathrm{N}$ yields a critical exponent $\gamma\simeq$ 0.45(4), placing CuCrP$_2$S$_6$ in a three dimensional Heisenberg universality regime.
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All authors C. S. Saramgi, L. F. Prager, S. Selter, Y. Shemerliuk, S. Aswartham, B. Büchner, H.-J. Grafe, K. M. Ranjith

Materials Science · Cross-listed from cond-mat.str-el

Band Renormalization in Monolayer MoS2 Induced by Multipole Screening

Woojoo Lee, Seungwoo Yoo, Marios Zacharias et al. (+2 more)

Dielectric screening plays a crucial role in shaping the electronic structure of two-dimensional (2D) materials. In 2D semiconductors, screened Coulomb interactions arising from the surrounding dielectric environment are known to induce band renormalization, which is typically understood as a rigid shift of the electronic bands. Here, we experimentally demonstrate that dielectric screening can also give rise to non-rigid, momentum-dependent band renormalization. Using temperature-dependent angle-resolved photoemission spectroscopy (ARPES), we observe pronounced changes in the electronic band structure of monolayer MoS2 on a highly oriented pyrolytic graphite (HOPG) substrate. The results indicate that temperature-driven variations in the effective interlayer separation modulate the dielectric screening experienced by monolayer MoS2. At room temperature, the screening behavior is well described by a momentum-independent monopole approximation, whereas at liquid-helium temperatures the screening evolves into a multipole-like regime, leading to momentum-dependent band shifts.
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All authors Woojoo Lee, Seungwoo Yoo, Marios Zacharias, Junho Choi, Young-Kyun Kwon

Materials Science

Disorder-induced chirality in superconductor-ferromagnet heterostructures revealed by neutron scattering and multiscale modeling

Annika Stellhorn, Juan G. C. Palma, Alicia Backs et al. (+10 more)

Chirality in superconductor-ferromagnet hybrids strongly influences phenomena such as the observable signatures of long-range triplet superconductivity, but its microscopic origin in nominally centrosymmetric ferromagnets is still unclear. Here, we combine structural characterization, polarization-analyzed grazing-incidence small-angle neutron scattering (PA-GISANS), first-principles calculations, and deep-learning-assisted multiscale modeling to study FePd and Nb/FePd heterostructures. Experimentally, we observe partial L1$_0$ order, atomic intermixing, anti-phase boundaries, and a depth-dependent defect gradient across the FePd layer, together with a finite net magnetic chirality at room temperature. The GISANS asymmetry indicates that the main chiral contribution lies in-plane, with an additional out-of-plane component associated with depth-dependent magnetic inhomogeneity. Theoretically, we show that chemical disorder in FePd, especially when combined with a compositional gradient, produces finite Dzyaloshinskii-Moriya interactions and stabilizes chiral finite-$\mathbf{q}$ magnetic modulations with mixed Bloch-Néel character. In the mesoscopic model, the resulting in-plane modulation length approaches the experimentally observed range. These results identify disorder and compositional gradients as intrinsic microscopic sources of net chirality in FePd-based films, showing that the observed chirality does not arise only from interface effects.
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All authors Annika Stellhorn, Juan G. C. Palma, Alicia Backs, Anders Bergman, Angela B. Klautau, Emmanuel Kentzinger, Connie Bednarski-Meinke, Steffen Tober, Elizabeth Blackburn, Juri Barthel, Nina-Juliane Steinke, Helena M. Petrilli, Ivan P. Miranda

Materials Science

A Route to Nonrelativistic Altermagnetic Spin Splitting via Ultrafast Light

Huang-Zhao-Xiang Chen, Lin-Ding Yuan, Wen-Hao Liu et al. (+3 more)

We identify a nonequilibrium route for generating altermagnetic spin splitting in antiferromagnet by ultrafast light. Unlike existing strategies, this route does not require relativistic angular-momentum transfer, static symmetry breaking, or auxiliary external fields. Using real-time time-dependent density functional theory, we demonstrate in the antiferromagnetic perovskite KNiF3 that linearly polarized light can induce momentum-dependent altermagnetic spin splitting by breaking the effective time-reversal symmetry through photoexcited charge redistribution and the resulting lattice distortion. We provide a general symmetry selection rule for this route. These results establish a mechanism for ultrafast control of altermagnetism and extend its material realization into the nonequilibrium regime.
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All authors Huang-Zhao-Xiang Chen, Lin-Ding Yuan, Wen-Hao Liu, Lin-Wang Wang, Jun-Wei Luo, Zhi Wang

Materials Science

Noble-Gas Solubility in Solid and Fluid Metallic Hydrogen

Jakkapat Seeyangnok, Udomsilp Pinsook and Graeme J Ackland

Metallic hydrogen dominates the deep interiors of giant planets, where trace elements interact with dense quantum matter under extreme pressure. We investigate the thermodynamic stability of noble-gas impurities (He, Ne, Ar, Kr, Xe) in metallic hydrogen at 500 GPa using ab initio molecular dynamics combined with first-principles free-energy calculations. In the solid metallic phase, all noble gases exhibit positive formation free energies, driven by unfavorable electronic enthalpy and zero-point vibrational contributions. By contrast, heavier noble gases (Ar, Kr, Xe) appear soluble in liquid hydrogen, while He and Ne phase separate. This crossover reflects a competition between electronic repulsion and disorder-driven stabilization intrinsic to the liquid phase. Our results reveal noble-gas retention in metallic hydrogen, providing a microscopic mechanism for noble-gas fractionation in giant-planet interiors.
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Materials Science

Effective electron coupling to phonon mechanical angular momentum in helical systems

Akihito Kato, Nobuhiko Yokoshi and Jun-ichiro Kishine

In chiral crystals, two types of phonon angular momenta have been introduced. One is crystal angular momentum (CAM) arising from the rotational or screw-rotational symmetry and the other is mechanical angular momentum (MAM) associated with the circular motion of atomic displacements about equilibrium positions. Recently, the electron-phonon coupling that respects the screw-rotational symmetry is derived, whereby the CAM between electrons and phonons is interconverted. Here, we show that, in addition to CAM, MAM can also be converted to the electronic degrees of freedom by deriving a second-order perturbative Hamiltonian proportional to phonon MAM. This finding highlights that the electronic motion is directly affected by phonon MAM, and consequently, that phonon degrees of freedom can play a crucial role in phenomena related to electronic orbital polarization.
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Materials Science

MatClaw: An Autonomous Code-First LLM Agent for End-to-End Materials Exploration

Chenmu Zhang and Boris I. Yakobson

Existing LLM agents for computational materials science are constrained by pipeline-bounded architectures tied to specific simulation codes and by dependence on manually written tool functions that grow with task scope. We present MatClaw, a code-first agent that writes and executes Python directly, composing any installed domain library to orchestrate multi-code workflows on remote HPC clusters without predefined tool functions. To sustain coherent execution across multi-day workflows, MatClaw uses a four-layer memory architecture that prevents progressive context loss, and retrieval-augmented generation over domain source code that raises per-step API-call accuracy to ${\sim}$99 %. Three end-to-end demonstrations on ferroelectric CuInP2S6 (machine-learning force field training via active learning, Curie temperature prediction, and heuristic parameter-space search) reveal that the agent handles code generation reliably but struggles with tacit domain knowledge. The missing knowledge, such as appropriate simulation timescales, equilibration protocols, and sampling strategies, is the kind that researchers accumulate through experience but rarely formalize. Two lightweight interventions, literature self-learning and expert-specified constraints, bridge these gaps, defining a guided autonomy model in which the researcher provides high-level domain knowledge while the agent handles workflow execution. Our results demonstrate that the gap between guided and fully autonomous computational materials research is narrower than ever before: LLMs already handle code generation and scientific interpretation reliably, and the rapid improvement in their capabilities will accelerate materials discovery beyond what manual workflows can achieve. All code and benchmarks are open-source.
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Materials Science

Unraveling Intrinsic Thermal Conductivity in Layered Conductive MOF Single Crystals

Jinkun Guo, Dongyang Wang, Zhiyi Li et al. (+8 more)

Layered conductive metal-organic frameworks (LCMOFs) show great promise in energy and electronics due to their high electrical conductivity and tunable pore structures. They are considered ideal "phonon-glass, electron-crystal" materials. However, their intrinsic thermal transport properties, particularly the thermal conductivity in the single-crystalline state, have never been explored before. The applicability of the Wiedemann-Franz law to such complex porous materials is a key scientific question to describe their thermoelectric relationship. We investigated single crystals of three LCMOFs (Cu3HHTP2, Co9HHTP4, Nd3HHTP2) using the microfabricated suspended device. Results showed ultralow thermal conductivities (0.075-0.194 W m-1 K-1) along the {\pi}-{\pi} stacking direction. Crucially, Nd3HHTP2 exhibited a high electrical conductivity of 398 S cm-1, yet its thermal conductivity (0.148 W m-1 K-1) was comparable to the other two LCMOFs with significantly lower electrical conductivities. Structural characterization revealed that the incommensurate modulation, and in-plane correlated disorder within the Nd3HHTP2 structure are the potential causes of strong phonon scattering and the observed ultralow thermal conductivity.
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All authors Jinkun Guo, Dongyang Wang, Zhiyi Li, Haoyang Zhang, Jiaxiang Zhang, Zeyue Zhang, Lei Sun, Junliang Sun, Jiawei Zhou, Chongan Di, Jinhu Dou

Materials Science

Nonlinear Magnetic Orbital Hall Effect Induced by Spin-Orbit Coupling

Hui Wang, Huiying Liu, Yanfeng Ge et al. (+6 more)

Electrical readout of 180$^\circ$ switching in strictly compensated collinear antiferromagnets remains a major challenge in antiferromagnetic spintronics. Electrical writing of perpendicularly magnetized ferromagnets by out-of-plane orbital torque remains an important challenge in orbitronics. In this work, we propose a second-order nonlinear magnetic orbital Hall effect in the source antiferromagnet as a simultaneous recipe for both difficulties. This orbitronics effect is induced by spin-orbit coupling and is odd in the Néel vector, thus is a unique effect that integrates both functionalities via electric control of the Néel vector in the source antiferromagnet. Our first-principles calculations in CuMnAs predict significant non-perturbative orbital effects from spin-orbit coupling, with a orbital Berry-curvature dipole mechanism. These findings unveil new possibilities opened by topological antiferromagnetic orbitronics.
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All authors Hui Wang, Huiying Liu, Yanfeng Ge, Xukun Feng, Jiaojiao Zhu, Jin Cao, Cong Xiao, Shengyuan A. Yang, Lay Kee Ang

Materials Science

Evolution from Landau Quantization to Discrete Scale Invariance Revealed by Quantum Oscillations in Topological Materials

Jiayi Yang, Nannan Tang, Yunxing Li et al. (+10 more)

Dirac materials have been a unique solid state platform for exploring relativistic quantum phenomena including supercritical atomic collapse, which leads to emergent discrete scale symmetry and logperiodic quantum oscillations. In the relativistic regime, the fundamental effect in quantum electrodynamics, vacuum polarization, can further modulate the atomic collapselike state by screening bare charges but is rarely harnessed in condensed matter system. Here, we report a continuous progression from low field Shubnikov de Haas oscillations to high field log periodic oscillations in the Dirac material HfTe5, with both phenomena modulated by Fermi surface anisotropy. This maps the transition from single particle Landau levels to an interaction-driven, discrete scale invariant energy spectrum of quasi-bound states. Crucially, our findings suggest vacuum polarization provides a compelling mechanism for renormalizing the effective impurity charge, quantitatively explaining the carrier-density dependent scale factor. By revealing the intricate interplay between Landau quantization, many body electronic screening, and scale-symmetry breaking, our results establish Dirac solids as a controllable platform for exploring relativistic vacuum effects and emergent novel symmetry.
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All authors Jiayi Yang, Nannan Tang, Yunxing Li, Jiawei Luo, Huakun Zuo, Gangjian Jin, Ziqiao Wang, Haiwen Liu, Yanzhao Liu, Donghui Guo, XinCheng Xie, Jian Wang, Huichao Wang

Thursday 2 April

Materials Science · Cross-listed from physics.comp-ph

Meta-optimization of maximally-localized Wannier functions

Sabyasachi Tiwari, Bruno Cucco, Viet-Anh Ha et al. (+1 more)

Maximally-localized Wannier functions are quantum wavefunctions resembling atomic orbitals that are used to describe electrons in condensed matter. Since their introduction in 1997, these functions have become ubiquitous in ab initio materials simulations, including applications in linear-scaling methods, strongly-correlated electron systems, quantum transport, electron-phonon interactions, and topological materials. Despite their widespread adoption in a vast software ecosystem, Wannier functions have not yet attained their fullest potential in the presence of entangled bands, as their optimization remains challenging and labor-intensive. Here, we introduce a universal meta-optimization method that leverages workflow abstraction and machine learning techniques like differential evolution and Bayesian optimization to generate globally optimized Wannier functions without human intervention. We demonstrate this approach through three applications: (i) autonomous interpolation of entangled band structures with millielectronvolt accuracy starting from coarse Brillouin zone grids, (ii) thousand-fold acceleration of fully ab initio Boltzmann transport calculations via the use of minimal coarse Brillouin zone grids, and (iii) ultra-fast high-throughput calculations of high-precision Wannier functions for large materials libraries. This work brings calculations that previously required supercomputers within the reach of personal computers.
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All authors Sabyasachi Tiwari, Bruno Cucco, Viet-Anh Ha, Feliciano Giustino

Materials Science

Temperature-dependent Raman spectra of 2H-MoS2 from Machine Learning-driven statistical sampling

Samuel Longo, Aloïs Castellano and Matthieu J. Verstraete

Molybdenum sulfides are in the spotlight of materials science thanks to their interesting properties for applications in optoelectronics, nanocomposites, lubricants, and catalysis. The structural characterization of Molybdenum sulfides is a crucial step to understand and tune their properties. Vibrational techniques, such as infrared and Raman spectroscopy, can directly link to structural features, but the experimental literature suffers from large variability. Theoretical calculations are a powerful tool complementing and explaining empirical measurements. The reliability of first-principles calculation depends on the level of approximation made, taking into account disorder, doping, or temperature to yield a good description of the phonon statistics and related measurable quantities, such as the infrared and Raman peaks. In this study we calculate the Raman spectrum of crystalline 2H-MoS2, including broadening and shifts due to thermal and anharmonic effects. Our results demonstrate excellent agreement with experimental measurements; notably, the calculated temperature trends in frequencies and linewidths align with empirical observations. These findings establish a robust computational framework, paving the way for similar studies on amorphous Molybdenum sulfides.
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Materials Science · Cross-listed from cs.CL

PolyJarvis: An LLM-Orchestrated Agent for Automated All-Atom Molecular Dynamics of Amorphous Homopolymers

Alexander Zhao, Achuth Chandrasekhar and Amir Barati Farimani

All-atom molecular dynamics (MD) simulations can predict polymer properties from molecular structure, yet their execution requires specialized expertise in force field selection, system construction, equilibration, and property extraction. We present PolyJarvis, a platform in which a planning agent produces a validated run plan that deterministic stage scripts execute through established simulation toolkits, Enhanced Monte Carlo (EMC) for system construction and LAMMPS for molecular dynamics, exposed as Model Context Protocol (MCP) servers, with a recovery agent consulted only on structured failures and within a fixed decision budget. Given a repeat-unit SMILES string and target properties, PolyJarvis constructs the amorphous cell, equilibrates it under a mechanized convergence gate, and computes target properties. Validation is conducted on seven amorphous homopolymers, each run as three replicates that share a protocol frozen per system and use independent random seeds, namely polyethylene (PE), atactic polystyrene (aPS), syndiotactic poly(vinyl chloride) (sPVC), poly(L-lactic acid) (PLLA), poly(ethylene glycol) (PEG), poly(ether ether ketone) (PEEK), and polysulfone (PSU). Against experimental references, 13 of 19 graded comparisons meet the acceptance criteria (density 5 of 7, glass transition 4 of 7, bulk modulus 4 of 5). The failures are concentrated in the PCFF systems: under-density of aPS and PEG, overestimated glass transitions of the stiff PLLA and PEEK backbones, and an overstiff PEG bulk modulus.
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Materials Science

AQVolt26: High-Temperature r$^2$SCAN Halide Dataset for Universal ML Potentials and Solid-State Batteries

Jiyoon Kim, Chuhong Wang, Aayush R. Singh et al. (+6 more)

The demand for safe, high-energy-density batteries has spotlighted halide solid-state electrolytes, which offer the potential for enhanced ionic mobility, electrochemical stability, and interfacial deformability. Accelerating their discovery requires extensive molecular dynamics, which has been increasingly enabled by universal machine learning interatomic potentials trained on foundational datasets. However, the dynamic softness of halides poses a stringent test of whether general-purpose models can reliably replace first-principles calculations under the highly distorted, elevated-temperature regimes necessary to probe ion transport. Here, we present AQVolt26, a dataset of 322,656 r$^2$SCAN single-point calculations for lithium halides, generated via high-temperature configurational sampling across $\sim$5K structures. We demonstrate that foundational datasets provide a strong baseline for stable halide chemistries and transfer local forces well, however absolute energy predictions degrade in distorted higher-temperature regimes. Co-training with AQVolt26 resolves this blind spot. Furthermore, incorporating Materials Project relaxation data improves near-equilibrium performance but degrades extreme-strain robustness without enhancing high-temperature force accuracy. These results demonstrate that domain-specific configurational sampling is essential for the reliable dynamic screening of halide electrolytes. Furthermore, our findings suggest that while foundational models provide a robust base, they are most effective for dynamically soft solid-state chemistries when augmented with targeted, high-temperature data. Finally, we show that near-equilibrium relaxation data serves as a task-specific complement rather than a universally beneficial addition.
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All authors Jiyoon Kim, Chuhong Wang, Aayush R. Singh, Tyler Sours, Shivang Agarwal, AJ Nish, Paul Abruzzo, Ang Xiao, Omar Allam