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Physics Condensed Matter Materials Science

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Monday 9 February

Materials Science

Hidden in-plane long-range order in an amorphized crystal

Yin Chen, Anthony E. Phillips, Cheng Fu et al. (+12 more)

Solid materials are commonly classified as crystalline or amorphous based on the presence or absence of long-range order.Metal-organic frameworks (MOFs), like other solids,also display markedly different properties and functions in these two phases. Here, we identify a previously unrecognized structural state that retains long-range in-plane translational order while losing order along the stacking direction. Hypothesized since 1941 but not experimentally verified, this intermediate phase emerges in a crystalline MOFs via controlled thermal desolvation, which selectively disrupts the intrinsically weak interlayer interactions while preserving macroscopic structural coherence. Although the resulting material appears amorphous under conventional characterization, systematic synchrotron PXRD, total X-ray scattering, and low-dose high resolution TEM reveal clear in-plane periodicity. This material spontaneously delaminates in water into uniform, high-quality two-dimensional crystalline nanosheets, forming stable colloidal suspensions and exhibiting superlubricity comparable to graphene - but at less than 0.1% of the production cost. Our discovery finds a missing link within the long-standing crystalline-amorphous dichotomy, while providing an inherently scalable route to high-quality 2D crystals, and offering a conceptual and practical advance in phase engineering.
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All authors Yin Chen, Anthony E. Phillips, Cheng Fu, Volodymyr Bon, Lei Liu, Xiaoxu Sun, Jiahui Wang, Na Lin, Ruize Xie, Guanqun Cai, Yutong Wang, Jing Ma, Yuhong Liu, Yu Han, Stefan Kaskel

Materials Science

Pressure induced electronic band evolution and observation of superconductivity in the Dirac semimetal ZrTe5

Sanskar Mishra, Nagendra Singh, Vinod K. Gangwar et al. (+8 more)

We report a comprehensive investigation of the pressure effects on the magnetotransport properties of the topological material ZrTe5 within 1 to 8 GPa pressure range. With increasing pressure, the characteristic peak (Tp) in its electrical resistivity first shifts to higher temperature and then moves quickly towards the lower temperature before disappearing eventually at 6 GPa. Beyond 6 GPa, the system exhibits metallic behavior across the entire temperature range, and superconductivity emerges below Tc = 1.8 K at 8 GPa. Based on the systematic magnetotransport measurement under pressure, we demonstrate that the superconductivity occurs following a significant electronic structure modulation possibly due to pressure induced structural changes near 6 GPa, which coincides with dramatic enhancement of the magnetoresistance (MR) reaching up to 1400 percent. Our experimental results are substantiated by density functional theory calculations as the application of pressure drastically alters the density of states near the Fermi level. Notably, multiple hole pockets emerge at the Fermi level from 4 GPa onward, and their contributions are further enhanced with increasing pressure. The combined experimental and theoretical investigation reveals a comprehensive evolution of electronic structure of Dirac semimetal ZrTe5 under pressure and suggest a possible link between the Fermi surface reconstruction in the pressure range of structural transition and emergence of superconductivity
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All authors Sanskar Mishra, Nagendra Singh, Vinod K. Gangwar, Rajan Walia, Jianping Sun, Genfu Chen, Dilip Bhoi, Sandip Chatterjee, Yoshiya Uwatoko, Jinguang Cheng, Prashant Shahi

Materials Science

Coupling between CaWO$_4$ phonons and Er$^{3+}$ dopants

Mikhael T. Sayat, Federico Pisani, Hin Lok Chang et al. (+8 more)

We investigate the lattice dynamics of CaWO$_4$, a promising host crystal for erbium-based quantum memories, using inelastic neutron scattering together with density-functional perturbation theory. The measured phonon dispersion along the (100), (001), and (101) reciprocal space direction reveals phonon bands extending up to 130 meV, with a gap between 60 and 80 meV, in good agreement with our calculations. From a symmetry analysis of the phonon eigenmodes, we identify eight Raman-active modes that can couple directly to the Er$^{3+}$ crystal-field operators, including a low-energy $B_g$ mode at 9.1 meV that is expected to play a dominant role in phonon-assisted spin-lattice relaxation. These results provide a microscopic description of the phonon bath in CaWO$_4$ and establish a basis for engineering phononic environments to mitigate the loss of stored quantum states and optimize Er-doped CaWO$_4$ for quantum-memory applications.
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All authors Mikhael T. Sayat, Federico Pisani, Hin Lok Chang, Yaroslav Zhumagulov, Kirrily C. Rule, Tom Fennell, Jakob Nunnendorf, Chee Kwan Gan, Oleg V. Yazyev, Ping Koy Lam, Jian-Rui Soh

Materials Science

Inverse orbital Hall effect induced terahertz emission enabled by a ferromagnet with quenched orbital moment in Fe/Pt/W trilayers

Chao Zhou, Lei Hao, Shaohua Zhang et al. (+10 more)

The inverse orbital Hall effect (IOHE) has recently attracted considerable attention as an emerging mechanism for terahertz (THz) emission based on ultrafast angular-momentum-to-charge conversion. Most experimental studies have focused on materials with strong spin-orbit coupling or pronounced orbital character, where sizable orbital Hall responses are expected. Elemental ferromagnets such as Fe are generally regarded as quenched orbital sources and are not expected to exhibit orbital-dominated THz emission. Here, we report a pronounced enhancement of THz emission in Fe/Pt/W trilayer heterostructures, despite the absence of detectable orbital contributions in the corresponding Fe/Pt and Fe/W bilayers. Thickness-dependent measurements reveal long-distance signal persistence, systematic delay accumulation, and pronounced pulse broadening with increasing W thickness. These features are inconsistent with diffusive spin transport and indicate that orbital angular momentum transport in the W layer, converted into charge current via the IOHE, becomes a dominant channel for THz emission in the trilayer configuration. Our results demonstrate that strong IOHE can emerge in heterostructures incorporating a quenched orbital ferromagnet, providing an effective route to enhance spintronic THz emitters through orbital Hall physics.
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All authors Chao Zhou, Lei Hao, Shaohua Zhang, Yaxuan Jin, Xianguo Jiang, Ning Yang, Li Zheng, Hao Meng, Chao Lu, Wendeng Huang, Yizheng Wu, Yan Zhou, Jia Xu

Materials Science · Cross-listed from math.CV

Mellin-Space Prony Representability of Linear Viscoelastic Models

Dimiter Prodanov

Linear viscoelastic materials are commonly described by continuous relaxation spectra, yet practical measurements and simulations employ discrete Prony series. In the Laplace frequency domain, the distinction is well understood: rational transfer functions admit finite Prony representations, while fractional models with branch cuts do not. This work provides a complementary and structurally deeper characterization in the Mellin transform domain. We prove that a viscoelastic modulus admits an exact finite Prony series if and only if the arithmetic pole lattices of its Mellin kernel align with the integer lattice of the constitutive kernel, and the associated residues satisfy decoupled first-order recurrences along aligned sublattices. Unlike the Laplace-domain rational/non-rational dichotomy, the Mellin criterion reveals the arithmetic geometry underlying finite representability, which requires Diophantine alignment of infinite pole progressions and the compatibility of their residues. Applying this criterion yields a complete model taxonomy. Classical spring-dashpot networks (Maxwell, standard linear solid) satisfy the alignment and recurrence conditions. In contrast, fractional models (power-law, Cole-Cole, Havriliak-Negami, Zener) and log-normal spectra violate one or both conditions and require infinite Prony ladders for exact representation. The framework thus shifts the question of finite network realizability from an algebraic condition on rational functions to a geometric condition on pole lattices, offering both a theoretical classification and a practical computational test.
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Materials Science

Giant Magnetocaloric Effect in a High-Spin Shastry-Sutherland Dipolar Magnet

Jianjian Gong, Junsen Wang, Junsen Xiang et al. (+15 more)

The Shastry-Sutherland lattice is a prototypical frustrated quantum magnet. It is notable for its exactly solvable dimer-singlet ground state and hosts a wealth of magnetic phenomena under external fields. Here, this work investigates the high-spin (S = 7/2) Eu-based magnet Eu2MgSi2O7 (EMSO) using low-temperature magnetothermal measurements and Monte Carlo simulations, revealing a giant magnetocaloric effect (MCE) in this Shastry-Sutherland compound. The entropy change peak value is found to be 55.0 J kg-1 K-1 under a field change of B = 0-4 T, approximately 1.5 times larger than the commercial Gd3Ga5O12 (GGG). Adiabatic demagnetization refrigeration achieves a lowest temperature of 151 mK, deeply into the sub-Kelvin regime. Furthermore, a distinctive cooling effect persists below about 1 T, a characteristic absent for conventional magnetic coolants. A dipolar Shastry-Sutherland model is introduced as a minimal model to describe this system; in particular, the experimentally revealed 1/3 magnetization pseudo-plateau can be ascribed to the presence of dipolar couplings between Eu2+ ions, further stabilized by the thermal fluctuations, explaining the persistent cooling effect. This work establishes EMSO as a novel platform for exploring the dipolar Shastry-Sutherland system and for sub-Kelvin adiabatic demagnetization refrigeration.
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All authors Jianjian Gong, Junsen Wang, Junsen Xiang, Zhaojun Mo, Lei Zhang, Xinyang Liu, Xuetong He, Lu Tian, Zhixing Ye, Huicai Xie, Xucai Kan, Xinqiang Gao, Zhenxing Li, Peijie Sun, Shouguo Wang, Wei Li, Baogen Shen, Jun Shen

Materials Science

Ozonation of Dielectric Fosters Self-Healing Efficiency in Metalized-Film Capacitors: Quantum-Chemical Simulation

Nadezhda A. Andreeva, Cuixia Liu and Vitaly V. Chaban

Metalized-film capacitors (MFCs) employ polymer organic dielectrics like polypropylene (PP) and polyimide (PI), in which self-healing is seen as a key advantage. However, the performance of self-healing depends on specific chemical mechanisms involved. The formation of semiconductive carbonaceous soot represents a critical failure risk. This study investigates how oxygen atom impregnation through ozonation of the dielectric material tunes the composition and electrical conductivity of breakdown products in the PP and PI systems with aluminum-zinc electrodes. We revealed, at the atomistic level, that oxygen atoms tend to remove a fraction of carbon atoms from the semiconductive soot by oxidizing carbon into carbon monoxide in both polymers. In PP, oxygen fraction linearly increases gas mass fraction, thereby reducing soot fraction. In PI, the gas/soot ratio effect of oxygen content is less drastic, still clearly positive. The PP soot conductivity decreases uniformly as larger fractions of oxygen atoms are added. In turn, the PI conductivity drops to ~1500 S/m quickly. The PI soot exhibits narrower band gaps compared to that of PP. The oxygen fraction non-monotonically tailors band gaps, which generally increase. To summarize, ozonation enhances MFC reliability by increasing gas species fraction and reducing soot conductivity. We hereby provide numerical molecular-level insights to rationalize self-healing performance enhancement through polymer ozonation.
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Materials Science

2D ferroelectric narrow-bandgap semiconductor Wurtzite' type alpha-In2Se3 and its silicon-compatible growth

Yuxuan Jiang, Xingkun Ning, Renhui Liu et al. (+17 more)

2D van der Waals ferroelectrics, particularly alpha-In2Se3, have emerged as an attractive building block for next-generation information storage technologies due to their moderate band gap and robust ferroelectricity stabilized by dipole locking. alpha-In2Se3 can adopt either the distorted zincblende or wurtzite structures; however, the wurtzite phase has yet to be experimental-ly validated, and its large-scale synthesis poses significant challenges. Here, we report an in-situ transport growth of centimeter-scale wurtzite type alpha-In2Se3 films directly on SiO2 substrates using a process combining pulsed laser deposition and chemical vapor deposition. We demonstrate that it is a narrow bandgap ferroelectric semiconductor, featuring a Curie tem-perature exceeding 620 K, a tunable bandgap (0.8-1.6 eV) modulated by charged domain walls, and a large optical absorption coefficient of 1.3 times 10 powers 6 per centemeter. Moreover, light absorption promotes the dynamic conductance range, linearity, and symmetry of the synapse devices, leading to a high recognition accuracy of 92.3 percent in a supervised pattern classification task for neuromorphic computing. Our findings demonstrate a ferroelectric polymorphism of In2Se3, highlighting its potential in ferroelectric synapses for neuromorphic computing.
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All authors Yuxuan Jiang, Xingkun Ning, Renhui Liu, Kepeng Song, Sajjad Ali, Haoyue Deng, Yizhuo Li, Biaohong Huang, Jianhang Qiu, Xiaofei Zhu, Zhen Fan, Qiankun Li, Chengbing Qin, Fei Xue, Teng Yang, Bing Li, Gang Liu, Weijin Hu, Lain-Jong Li, Zhidong Zhang

Materials Science · Cross-listed from physics.optics

Room Temperature Collective Blinking and Photon Bunching from CsPbBr3 Quantum Dot Superlattice

Qiwen Tan, Sudipta Seth, Boris Louis et al. (+7 more)

Development of quantum light sources and search for quantum systems capable of supporting collective many-body states are crucial for further progress of modern quantum technologies. Metal halide perovskite quantum dots (QDs) have emerged as a promising candidate for quantum light sources, as individual QDs are reliable single photon emitters even at room temperature. However, photon bunching, a key signature of collective many-body states, has been so far largely observed at cryogenic temperatures in perovskite materials, limiting their applications under ambient conditions. Here, we report the observation of collective blinking and photon bunching in perovskite QD superlattices at room temperature. Sub-wavelength-sized (100 - 500 nm) CsPbBr3 QD superlattices, fabricated via a self-assembly process, exhibit an unusual two-level blinking behavior similar to that of single QDs, and demonstrate photon bunching with a degree of up to 2.75. Time-resolved photoluminescence (PL) measurements and super-resolution imaging reveal that the superlattices have a significantly longer PL lifetime than individual QDs and that their emission is spatially confined to regions tens of nanometers in size. These observations suggest long-range exciton migration to a localized energy trap within the superlattice. Excitation power dependent degree of bunching and analysis of the bunching dynamics indicate that the photon bunching originates from exciton-biexciton cascade emission, a key mechanism for generating entangled photons. These findings establish perovskite QD superlattices as a promising platform for room-temperature collective optical phenomena and quantum light generation, advancing scalable quantum photonic technologies.
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All authors Qiwen Tan, Sudipta Seth, Boris Louis, Xiayan Wu, Nithin Pathoor, Toranosuke Takagi, Shun Omagari, Takumi Sannomiya, Johan Hofkens, Martin Vacha

Materials Science

Epitaxial Growth of Anisotropic SnSe on GaAs(001) via Step-Edge Orientation Control

Pooja D. Reddy, Zahra N. Heussen and Kunal Mukherjee

Epitaxial growth of orthorhombic SnSe on cubic substrates is challenging due to lattice-symmetry mismatch and anisotropic bonding. Here we demonstrate that epitaxial films with sharp interfaces can be achieved for layered SnSe grown directly on on-axis and 4 degree miscut GaAs(001) substrates. The substrate miscut strongly influences the growth morphology, evolving from spirals on on-axis GaAs to a terraced structure on miscut GaAs. X-ray diffraction reveals that on-axis GaAs supports SnSe with two in-plane orientation variants, whereas the miscut substrate stabilizes a single orientation and introduces a small out-of-plane tilt. Accordingly, in-plane optical anisotropy is enhanced in the single variant film compared to the double variant, as determined by cross-polar reflectance. High-resolution TEM shows that the SnSe/GaAs interface is atomically abrupt and incoherent, characteristic of quasi-van der Waals epitaxy. We find a pronounced tendency for the zigzag edges of SnSe to align parallel to step edges on both substrates, and we show that step-skipping nucleation and layer growth on the miscut substrate leads to the additional tilt. These results establish direct SnSe/GaAs heteroepitaxy as a route to integrate anisotropic layered semiconductors with cubic platforms, and show that miscut substrates provide additional control over in-plane anisotropy.
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Materials Science

Boosting high-current alkaline water electrolysis and carbon dioxide reduction with novel CuNiFe-based anodes

Nusrat Rashid, Shurui Yang, Galyam Sanfo et al. (+11 more)

The transition to a green hydrogen economy demands robust, scalable, and sustainable anodes for alkaline water electrolysis operating at industrial current densities (>1 A/cm2). However, achieving high activity and long-term stability under such conditions remains a formidable challenge with conventional catalysts. Here, we report a novel trimetallic CuNiFe anode fabricated through a rapid, single-step electrodeposition process at room temperature without organic additives. The catalyst exhibits an exceptionally low overpotential of <270 mV at 100 mA cm(-2) and operates stably for over 500 hours at 1 A cm(-2) in 30 wt% KOH. In a practical anion exchange membrane water electrolyzer (AEM-WE), the CuNiFe anode enables a current density of 2.5 A cm(-2) at only 2.5 V, with a voltage efficiency of 66.8%. Beyond water splitting, this anode also significantly enhances CO2 electrolysis, tripling the CO2 reduction current density and steering selectivity toward valuable multi-carbon products when paired with commercial copper cathodes. A cradle-to-gate life cycle assessment confirms that the CuNiFe anode reduces the carbon footprint by an order of magnitude and decreases environmental impacts by 40-60% across multiple categories compared to benchmark IrRuO2. Our work establishes a scalable, high-performance, and environmentally benign anode technology, paving the way for cost-effective electrochemical production of green hydrogen and carbon-neutral chemicals.
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All authors Nusrat Rashid, Shurui Yang, Galyam Sanfo, Isabelle Ewing, Zahra Ibrahim Albu, Xinjuan Li, Tianhao Wu, Prajna Bhatt, Mathieu Prevot, Laurent Piccolo, Mahmoud Zendehdel, Robert G. Palgrave, Caterina Ducati, Mojtaba Abdi-Jalebi

Sunday 8 February

Materials Science

Region-Resolved Interface Descriptors in III-nitride-nanocluster photocatalysts

Shuaishuai Yuan, Gunther G. Andersson, Gregory F. Metha et al. (+2 more)

Understanding how nanocluster cocatalysts modify the electronic structure of III-nitride surfaces is central to the rational design of efficient photocatalytic interfaces. Here, we introduce a region-resolved first-principles framework for analyzing GaN-, InGaN-, and ScGaN-based slabs decorated with six-atom elemental nanoclusters. Using a region-resolved projected local density of states (PLDOS) analysis, we separate electronic response of nanocluster-covered regions from that of uncovered semiconductor surface regions, revealing that semiconductor–nanocluster interfaces behave as laterally heterogeneous systems. In this picture, nanocluster-covered regions are associated with local band bending, charge injection, and nanocluster-induced gap states, whereas uncovered nitride regions retain surface-localized states and in-plane dipoles that may influence adsorbate interactions and water-activation pathways. These distinct regional responses motivate the definition of region-resolved interface descriptors, which are further integrated into an Interface Score: a physics-informed comparative metric that combines injection, activation, and interfacial-coupling contributions to rank heterogeneous model interfaces on a common descriptor basis. Machine-learning models trained on global and region-resolved descriptors are used primarily as interpretability tools to assess their correlation with single-H adsorption energetics. The results show that spatially averaged descriptors capture broad adsorption-energy trends, while region-resolved descriptors expose complementary local information related to interfacial electrostatics and charge separation. Together, this work establishes a descriptor framework for moving beyond spatially averaged electronic-structure analysis and for bridging first-principles calculations with experimental interpretation of heterogeneous photocatalytic interfaces.
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All authors Shuaishuai Yuan, Gunther G. Andersson, Gregory F. Metha, Zetian Mi, Hong Guo

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

From Connectivity to Rupture: A Coarse-Grained Stochastic Network Dynamics Approach to Polymer Network Mechanics

Shaswat Mohanty and Wei Cai

We introduce a coarse-grained stochastic network dynamics (CGSND) framework for modeling deformation and rupture in polymer networks. The method replaces explicit molecular dynamics (MD) or coarse-grained molecular dynamics (CGMD) with network-level evolution rules while retaining chain entropic elasticity and force-controlled bond failure. Under uniaxial loading, CGSND reproduces the characteristic nonlinear stress–stretch response of elastomeric networks, including a well-defined ultimate tensile strength and post-peak softening due to progressive bond rupture. Comparison with coarse-grained molecular dynamics (CGMD) simulations shows that CGSND captures the qualitative form of the stress response and the onset of catastrophic damage despite its rate-independent formulation. Analysis of rupture kinetics reveals a pronounced peak in the bond-breaking hazard rate near the ultimate tensile strength in both approaches. In addition, the distribution of broken segment lengths remains statistically indistinguishable from the initial network, indicating that rupture is not biased toward short or long chains. Finally, the evolution of the Gini coefficient of bond force magnitudes reveals strong force localization preceding failure. These results demonstrate that CGSND provides a computationally efficient and physically interpretable framework for connecting force localization and rupture kinetics to macroscopic failure in polymer networks.
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Materials Science · Cross-listed from physics.app-ph

Spatially and Temporally Resolved Mapping of Contact Electrification on Stand-Alone Ultrathin Glass Materials via Kelvin Probe Force Microscopy

Aayush Nayyar, Ruizhe Yang, Vashin Gautham et al. (+7 more)

Contact electrification (CE) remains a critical challenge in advanced material technologies where uncontrolled surface charging can compromise manufacturability, reliability, and performance in practical applications. Ultrathin glass with micrometer-scale thickness is a state-of-the-art specialty oxide material for flexible touchscreens in next-generation electronic devices. Here, we visualize and quantify CE-induced surface charges on ultrathin glass using sideband-mode Kelvin probe force microscopy (KPFM). Nanoscale atomic force microscopy (AFM) probes are used to scan and induce triboelectric charges on stand-alone glass surfaces under ultra-pure N$_2$ conditions. Time-dependent measurements reveal that surface charges on a 30~$\mu$m-thick glass sample decay from 4.47~V to 0.37~V over 240~minutes. Furthermore, electrostatic charges are found to exhibit capacitor-like discharging behavior primarily through the bulk material, yielding a long relaxation time constant of approximately 41~minutes. This behavior differs from the lateral surface discharging observed in thermally grown SiO$2$ thin films reported previously. A self-capacitance analytical model is developed to estimate the corresponding surface charge density ($\sigma$), yielding comparable values of 136.26~$\pm$~16.25~$\mu$C/m$^2$ at 30~$\mu$m and 131.44~$\pm$~28.41~$\mu$C/m$^2$ at 100~$\mu$m. Additionally, external bias applied to AFM tips can be used to enhance, suppress, or invert the intrinsic CE response of glass materials.
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All authors Aayush Nayyar, Ruizhe Yang, Vashin Gautham, Sagnik Das, Haiqing Lin, Andrew C. Antony, Dean Thelen, Mayukh Nath, Gabriel Agnello, Jun Liu

Materials Science · Cross-listed from physics.optics

Topological photonics in one-dimensional settings

Shiqi Xia, Ziteng Wang, Domenico Bongiovanni et al. (+7 more)

Over the past decade, topological photonics has emerged as a vibrant field, attracting significant attention and witnessing remarkable advancements. This growth can be attributed to its fundamental appeal and the unique opportunities it offers for unconventional control of light, promising innovations in next-generation photonic devices. At the heart of topological photonics lies the one-dimensional (1D) SSH model. Originally conceived to elucidate the physics of a molecular chain of polyacetylene, this model has found widespread applications in exploring a wide range of topological phenomena in photonics and beyond. In this chapter, we aim to provide an overview of topological photonics in one-dimensional (1D) settings. After briefly introducing paradigmatic 1D models, including the SSH, Rice-Mele, and AAH models, we review recent advances in experimental studies and applications of topological photonics based on 1D platforms. Our discussion highlights demonstrated examples, such as the nonlinear tuning of topological states in both Hermitian and non-Hermitian photonic SSH lattices, as well as nonlinear harmonic generation and topological lasing in SSH-type photonic microstructures. We further discuss characteristic topological phenomena in other representative 1D settings, including Floquet systems, topological pumping, quasicrystals, and synthetic non-Hermitian systems. Finally, we examine selected examples of two-dimensional (2D) photonic topological crystalline insulators that are closely linked to the SSH model. Towards the end, we summarize the chapter and provide a list of key contributions, together with an outlook on possible future directions in 1D topological photonics. While this review focuses specifically on 1D topological photonics, it is not intended to be comprehensive or exhaustive.
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All authors Shiqi Xia, Ziteng Wang, Domenico Bongiovanni, Dario Jukić, Daohong Song, Liqin Tang, Jingjun Xu, Roberto Morandotti, Hrvoje Buljan, Zhigang Chen

Materials Science

Unveiling the impact of anti-site defects in magnetic transitions of few-layer MnBi2Te4 by operando heating

Xinyu Chen, Jingjing Gao, Shuang Wu et al. (+11 more)

As the first experimentally discovered intrinsic magnetic topological insulator, MnBi2Te4 has attracted widespread attentions, providing a unique platform for the exploration of topological quantum phases, such as quantum anomalous Hall effect and axion insulator state. Despite the increasing number of potential factors affecting samples being identified, obtaining the high-quality device performance with desired topological quantum phases remains a challenge. In this work, by comparing the reflective magnetic circular dichroism (RMCD) of crystals with different defect densities that are characterized by atomically resolved scanning tunneling microscopy, we demonstrate that anti-site defects play an essential role in achieving ideal magnetic states. By measuring RMCD hysteresis loops with operando heating, we find that MnBi2Te4 few-layer samples are highly susceptible to thermal impact, even at temperature as low as 45{\deg}C. The magnetic behavior of heating-treated samples is akin to that of samples fabricated into devices, revealing the thermal impact on devices as well. Starting from few-layers with ideal layer-dependent magnetic order, thermal heating leads to the convergence of magnetization and transition fields between odd- and even-layers. The observed heating-induced magnetic evolution can serve as a valuable reference for assessing the sample quality or the density of anti-site defects. Our findings not only point out the long-standing hidden factor that arose controversies in MnBi2Te4, but also pave the way for controllably engineering the topological quantum phenomena.
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All authors Xinyu Chen, Jingjing Gao, Shuang Wu, Zhiwei Huang, Zhongxun Guo, Canyu Hong, Ruohan Chen, Mingyan Luo, Zhaochen Liu, Zeyuan Sun, Wei Ruan, Jing Wang, Yuanbo Zhang, Shiwei Wu

Materials Science

CDW Gap Collapse and Weyl State Restoration in Ta$_2$Se$_8$I via Coherent Phonons: A First-Principles Study

Tao Jiang, Jigang Wang and Yong-Xin Yao

Coherent phonon excitation offers a nonthermal route to control quantum phases of condensed matter. In this work, we employ first-principles calculations to investigate the phonon landscape of (TaSe$_4$)$_2$I in its charge-density-wave (CDW) phase. We identify nine symmetry-preserving Raman-active modes that can suppress the $\Gamma$-Z direct gap to the meV scale and render the system globally gapless by generating Weyl nodes at generic k points. Among them, the 2.52 THz CDW amplitude mode A(18) directly weakens the Ta-chain tetramerization, approaching a transient restoration of the uniform-chain geometry, while its low frequency and relatively small, Ta-dominated displacement make it the most efficient mode. Other Raman modes, dominated by Se vibrations, require significantly larger displacements to reach the Weyl-semimetallic regime and are generally less effective than A(18) at reducing the Ta-chain tetramerization. Furthermore, among the IR-active modes considered, the low-frequency B$_3$(7) mode (1.15 THz) provides the most favorable channel for nonlinear modulation of the A(18) potential. Although the coupling favors displacement toward the CDW-suppressing direction, the estimated indirect response remains far below that required for strong gap suppression. Direct excitation of A(18) therefore remains the most effective pathway to the Weyl-semimetallic regime.
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Materials Science

Epitaxial lift-off of La$_{2/3}$Sr$_{1/3}$MnO$_3$ membranes enabled by BaO sacrificial layers and restoration of the Curie temperature

Takahito Takeda, Daigo Matsubara, Yuki K. Wakabayashi et al. (+7 more)

Ultrathin complex-oxide membranes provide a powerful platform for strain engineering, interfacial control, and heterogeneous integration; however, their formation remains constrained by the availability and performance of suitable water-soluble sacrificial layers. This letter demonstrates that barium oxide (BaO) serves as a highly efficient and rapidly dissolving water-soluble sacrificial layer, enabling the epitaxial lift-off and transfer of ultrathin La$_{2/3}$Sr$_{1/3}$MnO$_3$ (LSMO) membranes onto SiO$_x$/Si substrates. LSMO membranes with a thickness of approximately 8 nm are released using a BaO sacrificial layer grown by molecular beam epitaxy, while high crystallinity is preserved and Ba interdiffusion is limited to a narrow interfacial region of approximately 0.5 nm. Post-transfer oxygen annealing at 600 ${}^\circ$C increases the Curie temperature ($T_C$) from 342 K to 346 K by eliminating Mn$^{2+}$ states associated with oxygen vacancies generated through oxygen extraction into the BaO layer. These results show that BaO provides a fast, scalable, and compositionally simple route for complex-oxide membrane release, while brief oxygen annealing is essential to restore the optimal Mn valence state and achieve the intrinsic high $T_C$.
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All authors Takahito Takeda, Daigo Matsubara, Yuki K. Wakabayashi, Kohei Yamagami, Munetoshi Seki, Hitoshi Tabata, Le Duc Anh, Masaki Kobayashi, Masaaki Tanaka, Shinobu Ohya

Materials Science

Influence of Elastic Oscillations on Nucleation in Metals

A.S. Nuradinov, O.V. Chistyakov, K.A. Sirenko et al. (+2 more)

This work is devoted to establishing the mechanisms of elastic oscillation influence on nucleation processes in metal melts. The method of physical modeling with low-temperature metallic alloys (Wood and Rose) and transparent organic media (salol, camphene, diphenylamine) was used. It was established that vibration and ultrasound significantly reduce the supercooling required to initiate crystallization. The effectiveness of the influence significantly increases for samples with solid substrates. The hypotheses about the influence through changes in melt viscosity and the exclusive role of cavitation were experimentally refuted. The transition from pre-cavitation to cavitation ultrasound regime is not accompanied by qualitative changes in the influence on nucleation. The mechanism of elastic oscillation influence is substantiated, which consists in mechanical impact on adsorbed crystal nuclei on the surfaces of solid substrates. Elastic oscillations increase the nucleation rate by creating growth steps (dislocations) on the surfaces of adsorbed nuclei as a result of mechanical friction of solid substrates and cavitation erosion. The results have fundamental significance for understanding the physical nature of metal crystallization and practical application for developing technologies for controlling structure formation.
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All authors A.S. Nuradinov, O.V. Chistyakov, K.A. Sirenko, I.A. Nuradinov, D.O. Derecha

Materials Science

Proton Quantum Effects on Electronic Excitation in Hydrogen-bonded Organic Solid: A First-Principles Green's Function Theory Study

Sampreeti Bhattacharya, Jianhang Xu, Ruiyi Zhou et al. (+1 more)

Nuclear quantum effects of protons on electronic excitations in hydrogen-bonded organic materials remains underexplored. In theoretical studies, modeling excitons in these extended systems is particularly difficult because they tend to have a large exciton binding energy and sometimes exhibit charge transfer character. We demonstrate how first-principles Green's function theory combined with the nuclear-electronic orbital method enables us to examine the nature of excitons in a prototypical organic solid of eumelanin, for which the extensive hydrogen bonds have been proposed to facilitate the formation of delocalized excitons. We investigate how the quantization of protons impacts electronic excitations. We discuss the extent to which the resulting proton quantum effects can be described as being derived from structure and how they induce molecular-level anisotropy for the excitons in the organic solid.
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All authors Sampreeti Bhattacharya, Jianhang Xu, Ruiyi Zhou, Yosuke Kanai

Materials Science · Cross-listed from cond-mat.mes-hall

Spin Splitter and Inverse Effects in Altermagnetic Hybrid Structures

Nicolás Sigales, Tim Kokkeler, Gonzalo de Polsi et al. (+1 more)

We provide a theoretical description of diffusive charge and spin transport in hybrid devices containing altermagnets. Based on recently derived drift–diffusion equations for coupled charge and spin dynamics and general boundary conditions, our approach provides a unified description of the spin-splitter effect, i.e., the conversion of charge currents into spin currents, and its inverse in terms of experimentally accessible parameters. We analyze, analytically and numerically, the spin-splitter effect, demonstrating that an injected spin accumulation generates a measurable voltage difference across the transverse direction in the altermagnet. Motivated by a recent experiment, we also analyze a nonlocal spin-valve geometry in which an altermagnetic strip injects spin into a diffusive normal metal. We derive the resulting nonlocal voltage detected by a ferromagnetic electrode as a function of the relative orientation of the N'eel vector and the ferromagnetic polarization, accounting for the main experimental findings. For this setup, we further address spin precession during diffusive transport by analyzing the spin Hanle effect. Our results provide theoretical explanations and predictions for several altermagnet hybrid structures.
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All authors Nicolás Sigales, Tim Kokkeler, Gonzalo de Polsi, Sebastian Bergeret

Materials Science

Bernal Stacking and Symmetry-Inequivalent Antiferromagnetism in MSi$_2$N$_4$ Heterobilayers

Brandon Pedroza-Rojas, David W. Facemyer and Ariadna Sánchez-Castillo

Layered MA$_2$Z$_4$ compounds, structural relatives of MoS$_2$ discovered in 2020, exhibit rich magnetic behavior arising from reduced dimensionality, noncentrosymmetric lattice symmetries, and stacking-dependent exchange interactions. Here, we investigate Bernal-like stackings in H-phase MA$_2$Z$_4$ (M = Mn and Fe; A = Si; Z = N) monolayers and bilayers by combining first-principles spin-dependent relaxation energies with a localized-spin Heisenberg description. From density-functional calculations, we extract the dominant intralayer exchange couplings up to third-nearest neighbors and the leading interlayer exchanges up to second-nearest neighbors, enabling construction of an effective bilayer spin Hamiltonian. We first analyze interface-driven proximity effects within a ferromagnetic reference configuration, demonstrating how recovery of AB-type stacking and spin alignment–while varying only the transition-metal species–provides a route for selectively tuning magnetic order and symmetry breaking within the P$\bar{6}$m2 space group. Building on this microscopic understanding of the bonding environment, we then examine antiferromagnetic ordering tendencies in the coupled layers. Exact diagonalization of the resulting bilayer Hamiltonian reveals the magnetic ground state and low-lying excitation spectrum, showing that the interlayer exchange is not merely perturbative but competes directly with intralayer interactions in stabilizing the observed spin configurations. These results establish Bernal-stacked MA$_2$Z$_4$ bilayers as a platform in which stacking geometry and exchange hierarchy jointly govern magnetic reconstruction, offering a controlled pathway toward domain selection and spin-texture engineering in low-dimensional van der Waals materials.
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Materials Science

Sequential versus Manifold Bayesian Optimization under Realistic Experimental Time Constraints

Boris Slautin and Sergei Kalinin

Bayesian optimization (BO) is widely used for autonomous materials discovery, yet its classical sequential formulation is insufficient for design of experimental workflows that often combine parallel or batch synthesis with inherently serial characterization. Methods such as combinatorial spread libraries and printed libraries sample a defined low-D manifold in the chemical space of the system. Here, we introduce a time-aware framework for comparing sequential and manifold BO under experimentally realistic constraints. By explicitly modeling synthesis and characterization times, we define an effective experimental time metric that enables fair, time-normalized benchmarking of optimization strategies. Using numerical experiments in ternary and quaternary compositional spaces, we show that sequential BO remains optimal for short-term experiments or when batching provides no effective time advantage, whereas manifold BO becomes favorable once multiplexed synthesis enables faster accumulation of measurements. We identify a small set of physically interpretable parameters that govern the transition between these regimes. These results establish a general, experimentally grounded framework for selecting optimization strategies in self-driving laboratories and autonomous materials discovery workflows. The accompanying analysis code is publicly available at https://github.com/Slautin/2025_GP_BO_Manifolds.
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Materials Science · Cross-listed from cond-mat.str-el

Electronic Structure of Epitaxial Films of the Bilayer Strontium Ruthenate: Sr$_{3}$Ru$_2$O$_{7}$

Sethulakshmi Sajeev, Arnaud P. Nono Tchiomo, Brendan D. Faeth et al. (+10 more)

We report a combined study of the low-energy electronic band structure of epitaxial Sr$_3$Ru$_2$O$_7$ films using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT). To investigate the effects of substrate dependence on the band structure, Sr$_3$Ru$_2$O$_7$ thin films are epitaxially grown on SrTiO$_3$ (STO) and (LaAlO$_{3}$)$_{0.3}$(Sr$_{2}$TaAlO$_{6}$)$_{0.7}$ (LSAT) substrates using molecular beam epitaxy. The measured and calculated Fermi-surfaces clearly show substantial changes in the Fermi surface topologies that originate from the underlying strain states. The compressively strained film grown on LSAT exhibits Fermi-surface features consistent with an orthorhombic-like symmetry; and the tensile-strained film grown on STO features a tetragonal-like surface symmetry. In addition, the ARPES data for both films indicate weakly dispersive spectral features within $\sim15~\text{meV}$ below the Fermi level. These observations underscore the strong sensitivity of the electronic structure of Sr$_3$Ru$_2$O$_7$ to epitaxial strain and establish a foundation for future efforts to tune correlated phases in this bilayer ruthenate.
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All authors Sethulakshmi Sajeev, Arnaud P. Nono Tchiomo, Brendan D. Faeth, Evan Krysko, Olivia Peek, Matthew J. Barone, Jordan Shields, Neha Wadehra, Garu Gebreyesus, Divine Kumah, Richard M. Martin, Darrell G. Schlom, Prosper Ngabonziza

Saturday 7 February

Materials Science · Cross-listed from cs.ET

Full-Field Damage Monitoring in Architected Lattices Using In situ Electrical Impedance Tomography

Akash Deep, Andrea Samore, Alistair McEwan et al. (+2 more)

Electrical impedance tomography (EIT) enables non-invasive, spatially continuous reconstruction of internal conductivity distributions, providing full field sensing beyond conventional point measurements. Here, we report the first in situ implementation of EIT within a tunable architected lattice materials framework, enabling systematic exploration across a broad lattice design space while achieving real time monitoring of damage evolution, including early stage, prefracture events, in 3D printed multifunctional lattice composites. Lattices are designed via Voronoi based branch trunk branch motifs inspired by 2D wallpaper symmetries and fabricated using CNT infused photocurable resins, with nanoscale filler dispersion confirmed by field emission scanning electron microscopy. Sixteen electrodes distributed along the lattice periphery enable EIT measurements during quasi static tensile loading. Conductivity maps reconstructed using adjacent and across current injection schemes resolve sequential ligament fracture with high temporal resolution, with localised conductivity loss quantitatively coinciding with fracture sites, including regions remote from electrodes. Architectural tunability allows systematic control of EIT imaging sensitivity to early stage damage, while pronounced resistance discontinuities at failure further corroborate spatial localisation; global end to end resistance measurements complement macroscopic stress strain responses. Collectively, these results establish in situ EIT as a scalable, full field sensing modality for architected multifunctional materials, providing an experimentally validated pathway toward autonomous, intelligent materials and data rich material states that can inform digital twin frameworks for structural, biomedical, and energy related applications.
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All authors Akash Deep, Andrea Samore, Alistair McEwan, Andrew McBride, Shanmugam Kumar

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

Topological and Planar Hall Effect in Monoclinic van der Waals Ferromagnet NbFeTe$_2$

Suchanda Mondal, Shubhankar Roy, Poulami Manna et al. (+1 more)

Two-dimensional (2D) van der Waals (vdW) ferromagnets have emerged as a critical class of quantum materials for next-generation, low-dimensional spintronic devices. In this study, we report a comprehensive study of the transport properties of the layered soft ferromagnet $\text{NbFeTe}_2$. We report the first observation of the topological Hall effect (THE) and the planar Hall effect (PHE) in metallic $\text{NbFeTe}_2$. THE signatures persist up to 45 K, while PHE remains evident well above Curie temperature ($T_C$). The observed negative longitudinal magnetoresistance, along with the PHE, provides strong evidence for a nontrivial electronic band structure. The coexistence of perpendicular magnetic anisotropy and a substantial THE: two key properties that are highly desirable for future spintronics applications, makes monoclinic vdW ferromagnetic $\text{NbFeTe}_2$ a promising platform to advance spintronics applications.
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All authors Suchanda Mondal, Shubhankar Roy, Poulami Manna, Ravi Prakash Singh

Materials Science

Acoustic wave scattering by spatio-temporal interfaces

J. Galiana, J. Redondo, R. Picó et al. (+1 more)

Space-time materials are obtained by modulating a physical medium with a traveling-wave perturbation of one or several of its constitutive parameters, such as the density or the bulk modulus in the case of acoustic materials. When this modulation has the form of a moving and abrupt (subwavelength) transition between two parameter values, we refer to a spatio-temporal interface, which may be considered as a building block for more complex space-time materials. This work considers the problem interaction and scattering of acoustic waves with a single spatio-temporal interface, and a sequence of two interfaces forming a slab. Several regimes defined by the relation between the sound propagation velocities and the interface velocity (namely subsonic, intersonic, and supersonic regimes) are discussed. Analytical expressions for the frequency conversions and scattering coefficients are obtained, and compared with numerical simulations based on an equivalent FTFD squeme.
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All authors J. Galiana, J. Redondo, R. Picó, V. J. Sánchez-Morcillo

Materials Science

Thermal Stability and Phase Transformation of Conductive $\alpha$-$(\mathrm{Al}_{x}\mathrm{Ga}_{1-x})_{2}\mathrm{O}_{3}/\mathrm{Ga}_{2}\mathrm{O}_{3}$ Heterostructures on Sapphire Substrates

Botong Li, Shisong Luo, Jaeheon Jung et al. (+10 more)

Thermal stability and phase transformation of conductive $\alpha$-$(\mathrm{Al}_{0.16}\mathrm{Ga}_{0.84})_{2}\mathrm{O}_{3}/\mathrm{Ga}_{2}\mathrm{O}_{3}$ heterostructures on sapphire substrates were investigated using in situ high-temperature X-ray diffraction (HT-XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Conductive $\alpha$-$(\mathrm{Al}_{0.16}\mathrm{Ga}_{0.84})_{2}\mathrm{O}_{3}/\mathrm{Ga}_{2}\mathrm{O}_{3}$ heterostructures with fluorine (F) doping were grown by mist chemical vapor deposition on sapphire substrates, achieving a Hall mobility of $28~\mathrm{cm^{2}\,V^{-1}\,s^{-1}}$ and an electron concentration of $1.4\times10^{20}~\mathrm{cm^{-3}}$. The heterostructures exhibited thermal stability up to approximately $550$–$
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All authors Botong Li, Shisong Luo, Jaeheon Jung, Bobby G. Duersch, Cheng Chang, Lucas Lau, Zonghao Zhang, Jianhua Li, Hunter Ellis, Imteaz Rahaman, Roy Byung Kyu Chung, Kai Fu, Yuji Zhao

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

Turning non-superconducting elements into superconductors by quantum confinement and proximity

Giovanni A. Ummarino and Alessio Zaccone

Elemental good metals, including noble metals (Cu, Ag, Au) and several $s$-block elements, do not exhibit superconductivity in bulk at ambient pressure, mainly due to weak electron-phonon coupling that cannot overcome Coulomb repulsion. Quantum confinement in ultra-thin films reshapes the electronic spectrum and the density of states near the Fermi level, producing strong, often non-monotonic, thickness dependencies of the critical temperature in established superconductors. Here, we examine whether confinement alone, or combined with proximity effects, can induce superconductivity in metals that are non-superconducting in bulk form. We review recent theoretical progress and introduce a unified framework based on a confinement-generalized, isotropic one-band Eliashberg theory, where the normal density of states becomes energy dependent and key parameters ($E_F$, $\lambda$, $\mu^$) acquire explicit thickness dependence. By numerically solving the Eliashberg equations using ab initio or experimentally determined electron-phonon spectral functions $\alpha^2F(\Omega)$ and Coulomb pseudopotentials $\mu^$, and without adjustable parameters, we compute the critical temperature $T_c$ as a function of film thickness for representative noble, alkali, and alkaline-earth metals. The results predict that superconductivity emerges only in selected cases and within extremely narrow thickness windows, typically at sub-nanometer scales ($L \sim 0.4-0.6$ nm), indicating strong fine-tuning requirements for confinement-induced superconductivity in good metals. We also consider layered superconductor/normal-metal systems where confinement and proximity effects coexist. In these heterostructures, a substantial enhancement of the critical temperature is predicted, even when the constituent materials are non-superconducting or weak superconductors in bulk form.
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Materials Science · Cross-listed from cs.AI

MSP-LLM: A Unified Large Language Model Framework for Complete Material Synthesis Planning

Heewoong Noh, Gyoung S. Na, Namkyeong Lee et al. (+1 more)

Material synthesis planning (MSP) remains a fundamental and underexplored bottleneck in AI-driven materials discovery, as it requires not only identifying suitable precursor materials but also designing coherent sequences of synthesis operations to realize a target material. Although several AI-based approaches have been proposed to address isolated subtasks of MSP, a unified methodology for solving the entire MSP task has yet to be established. We propose MSP-LLM, a unified LLM-based framework that formulates MSP as a structured process composed of two constituent subproblems: precursor prediction (PP) and synthesis operation prediction (SOP). Our approach introduces a discrete material class as an intermediate decision variable that organizes both tasks into a chemically consistent decision chain. For SOP, we further incorporate hierarchical precursor types as synthesis-relevant inductive biases and employ an explicit conditioning strategy that preserves precursor-related information in the autoregressive decoding state. Extensive experiments show that MSP-LLM consistently outperforms existing methods on both PP and SOP, as well as on the complete MSP task, demonstrating an effective and scalable framework for MSP that can accelerate real-world materials discovery.
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All authors Heewoong Noh, Gyoung S. Na, Namkyeong Lee, Chanyoung Park