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Physics Condensed Matter

cond-mat Watch Condensed Matter

Wednesday 10 December

Materials Science

Translating Chirality into Multidirectional Motion through Broadband Chiroptical MXenes

Wookjin Jung, Dongkyu Lee, Yonghee Lee et al. (+2 more)

The integration of chirality into functional materials enables control of light-matter interactions beyond binary illumination (on/off). Conventional photoactuators rely on binary modulation, limiting them to unidirectional motion. In contrast, we introduce a ternary optical logic paradigm where actuation direction is encoded by the handedness of circularly polarized light (CPL). Here, we establish a chiral Ti$_{3}$C$_{2}$T$_{x}$ MXene platform bridging molecular chirality and mechanical actuation. Phenylalanine enantiomers are covalently anchored onto MXene nanoflakes via chiral nanopainting. The 2D confinement forces ligands into vertically aligned supramolecular networks. Interlayer-spacing analysis and simulations corroborate that such supramolecular networks unlock exceptionally broadband circular dichroism from the ultraviolet to the near-infrared. This supramolecular chirality synergizes with MXene's plasmonic properties to drive handedness-dependent photothermal conversion, with a 30% differential temperature rise between matched and mismatched CPL. Embedding this chiral MXene into thermoresponsive hydrogels realizes, to the best of our knowledge, the first CPL-driven soft actuator that implements LCP/RCP/off as a ternary input to program multidirectional deformation based on a photothermal mechanism. This molecular-to-macroscopic translation demonstrates a new paradigm for chirality-encoded soft robotics and adaptive photonics.
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All authors Wookjin Jung, Dongkyu Lee, Yonghee Lee, Ki Hyun Park, Jihyeon Yeom

Strongly Correlated Electrons

Low-dimensionality-induced tunable ferromagnetism in SrRuO$_3$ ultrathin films

Jinyoung Kim, Minjae Kim, Donghan Kim et al. (+5 more)

Quantum materials near electronic or magnetic phase boundaries exhibit enhanced tunability, as their emergent properties become highly sensitive to external perturbations. Here, we demonstrate precise control of ferromagnetism in a SrRuO$_3$ ultrathin film, where a high density of states (DOS), arising from low-dimensional quantum states, places the system at the crossover between a non-magnetic and bulk ferromagnetic state. Using spin- and angle-resolved photoemission spectroscopy (SRPES/ARPES), transport measurements, and theoretical calculations, we systematically tune the Fermi level via electron doping across the high-DOS point. We directly visualize the spin-split band structure and reveal its influence on both magnetic and transport properties. Our findings provide compelling evidence that magnetism can be engineered through DOS control at a phase crossover, establishing a pathway for the rational design of tunable quantum materials.
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All authors Jinyoung Kim, Minjae Kim, Donghan Kim, Sungsoo Hahn, Younsik Kim, Minsoo Kim, Byungmin Sohn, Changyoung Kim

Statistical Mechanics · Cross-listed from physics.soc-ph

Functional Percolation: Criticality of Form and Function

Galen J. Wilkerson

Understanding how network structure constrains and enables information processing is a central problem in the statistical mechanics of interacting systems. Here we study random networks across the structural percolation transition and analyze how connectivity governs realizable input-output transformations under cascade dynamics. Using Erdos-Renyi networks as a minimal ensemble, we examine structural, functional, and information-theoretic observables as functions of mean degree. We find that the emergence of the giant connected component coincides with a sharp transition in realizable information processing: complex input-output response functions become accessible, functional diversity increases rapidly, output entropy rises, and directed information flow, quantified by transfer entropy, extends beyond local neighborhoods. We term this coincidence of structural, functional, and informational transitions functional percolation, referring to a sharp expansion of the space of realizable input-output functions at the percolation threshold. Near criticality, networks exhibit a Pareto-optimal tradeoff between functional complexity and diversity, suggesting that percolation criticality may provide a general organizing principle of information processing capacity in systems with local interactions and propagating influences.
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Superconductivity

Bulk superconductivity in the kagome metal YRu3B2

Tobi Gaggl, Ryo Misawa, Markus Kriener et al. (+3 more)

Materials with a kagome sublattice have been heavily studied recently for their exotic electronic band structure, structural frustration, high-temperature charge order transitions, and unconventional electron-phonon coupling. In LaRu3Si2, it was proposed that electronic flat bands conspire with the characteristic phonon spectrum of the kagome lattice to drive enhanced superconductivity at Tc = 7 K. Here, we report bulk superconductivity in the structural analogue YRu3B2, which hosts a structurally pristine kagome lattice. We observe a superconducting transition at Tc = 0.7 K through magnetization, resistivity, and heat-capacity measurements in this novel kagome metal.
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All authors Tobi Gaggl, Ryo Misawa, Markus Kriener, Yuki Tanaka, Rinsuke Yamada, Max Hirschberger

Strongly Correlated Electrons

Modified Kondorsky Domain Reversal in Microstructured Phase-Separated Manganites

Monique Kubovsky, Dylan Tagrin and Amlan Biswas

The hole-doped manganite (La$_{1-y}$Pr$_{y}$)$_{0.67}$Ca$_{0.33}$MnO$_3$ (LPCMO) shows electronic phase separation between ferromagnetic metallic (FMM) and anti-ferromagnetic charge-ordered insulating (AFM-COI) regions. In this study, (La$_{0.5}$Pr$_{0.5}$)$_{0.67}$Ca$_{0.33}$MnO$_{3}$ (LP5CMO) microstructures were fabricated using photolithography on thin films grown on (110) NdGaO$_3$ (NGO) substrates. We investigated the domain reversal mechanism of these microstructures through magnetotransport measurements. Our results demonstrate that, while bulk (unpatterned) films follow the standard Kondorsky model for domain reversal, the microstructures obey a modified Kondorsky model. This difference indicates that local magnetic fields from reversed domains significantly influence the coercive field in confined geometries. Although we did not observe a strong electric field effect, this study establishes that magnetotransport measurements are a feasible method for probing the competition between shape and magnetocrystalline anisotropy in manganite microstructures, which could provide an alternative path for controlling magnetic domains at low current densities.
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Materials Science

Single-crystalline high-quality beta-Ga2O3 pseudo-substrate on sapphire through sputtering for epitaxial deposition

Guangying Wang, Shuwen Xie, William Brand et al. (+10 more)

Solid-phase epitaxy (SPE) of beta-Ga2O3 thin films by radio-frequency (RF) sputtering and then crystallized through high-temperature post-deposition annealing is employed on sapphire substrates, yielding a high-quality pseudo-substrate for subsequent buffer growth via MOCVD and LPCVD. Low roughness (<0.5 nm) and sharp single-crystalline diffraction peaks corresponding to the (-201), (-402), and (-603) reflections of beta-Ga2O3 were observed in the SPE beta-Ga2O3 film and the subsequent epitaxial buffer layer. N-doped Ga2O3 film on SPE Ga2O3 film grown by LPCVD showed step-assisted growth mode with reasonable electronic behavior with 45 cm^2/V-s mobility at a bulk carrier concentration of 1.3e17 cm^-3. These results suggest that SPE Ga2O3 is a promising pathway to advance the development of beta-Ga2O3 on foreign substrates.
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All authors Guangying Wang, Shuwen Xie, William Brand, Saleh Ahmed Khan, Ahmed Ibreljic, Darryl Shima, Yueying Ma, Brahmani Challa, Fikadu Alema, Andrei Osinsky, Anhar Bhuiyan, Ganesh Balakrishnan, Shubhra S. Pasayat

Materials Science

A physics-augmented neural network framework for modeling and detecting thermo-visco-plastic behavior

Reese E. Jones, Asghar Jadoon, D. Thomas Seidl et al. (+1 more)

Although considerable attention has been devoted to the development of models for isothermal, rate-independent plasticity, many high-consequence performance assessments involve viscoplastic processes that generate substantial heat. In addition, materials may transit from a nearly isothermal, rate-independent regime to a viscous, temperature-dependent regime during these processes, which makes modeling more challenging. In this work, we develop a physics-augmented neural network (PANN) framework for modeling general temperature-dependent, rate-dependent inelastic processes firmly based on physical principles, including the second law of thermodynamics and coordinate equivariance. These embedded properties are enabled by a number of architectural innovations in the structure and training of an input convex and potential-based neural ordinary differential equation framework. The resulting neural network models are capable of representing a wide spectrum of rate- and temperature-dependence ranging from isothermal, rate-independent elastic-plastic phenomenology to rate-dependent fully viscous inelastic behavior, as we demonstrate. We also show that the framework is capable of modeling complex microstructural inelasticity and predicting the conversion of plastic work to heating when calibrated to stress-temperature observations.
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All authors Reese E. Jones, Asghar Jadoon, D. Thomas Seidl, Jan N. Fuhg

Strongly Correlated Electrons

Observation of ubiquitous charge correlations and hidden quantum critical point in hole-doped kagome superconductors

Ilija K. Nikolov, Giuseppe Allodi, Adrien Rosuel et al. (+9 more)

The interplay between superconductivity and charge-density wave (CDW) order, and its evolution with carrier density, is central to the physics of many quantum materials, notably high-$T_c$ cuprates and kagome metals. Hole-doped kagome compounds exhibit puzzling double-dome superconductivity and, as chemical substitution inevitably introduces quenched disorder, their properties remain poorly understood. Here, by leveraging the sensitivity of nuclear quadrupole resonance to local and static orderings, we uncover new features, primarily the incipient and fragmented CDW phases, in the charge landscape of CsV$_3$Sb$_{5-x}$Sn$_x$. Static CDW puddles are observed well above the transition temperature, a hallmark of pinning by defects. Their doping and temperature evolution indicate that, in the absence of disorder, the inverse Star-of-David $\pi$-shifted (ISD-$\pi$) CDW order would vanish near $x=0.12$, between the two superconducting domes. This critical doping represents a hidden quantum critical point. Nevertheless, the ISD-$\pi$ pattern persists well beyond previous reports, although its volume fraction is progressively reduced up to the critical doping at which it saturates. We establish that carrier doping promotes fragmentation of the ISD-$\pi$ order, whereas randomness preserves the ISD-$\pi$ patches.
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All authors Ilija K. Nikolov, Giuseppe Allodi, Adrien Rosuel, Ginevra Corsale, Anshu Kataria, Pietro Bonfà, Roberto De Renzi, Andrea Capa Salinas, Stephen D. Wilson, Marc-Henri Julien, Samuele Sanna, Vesna F. Mitrović

Materials Science · Cross-listed from physics.optics

Scalable van der Waals Photonics: High-Refractive-Index Gallium Sulfide Films with Single-Crystal Optical Properties

Aleksandr Slavich, Georgy Ermolaev, Dmitriy Grudinin et al. (+15 more)

The integration of high-refractive-index dielectrics into scalable photonic architectures is foundational to advancing integrated circuits and augmented reality (AR) displays. Van der Waals (vdW) materials offer exceptional optical properties, including high refractive indices and giant anisotropy, but their implementation is constrained by the small area and uncontrolled thickness of mechanically exfoliated flakes. Here, we demonstrate that atomic layer deposition (ALD) grown gallium sulfide (GaS) overcomes the trade-off between high optical performance and manufacturability, emerging as a large-scale vdW dielectric platform. Through rigorous optical and structural benchmarking against pristine single crystals, we establish that the optical constants (n, k) of ALD-GaS are virtually indistinguishable from single-crystal counterparts. By leveraging the retained out-of-plane anisotropy, we demonstrate that ALD-GaS enables superior suppression of crosstalk in densely integrated waveguides compared to conventional scalable high-index platforms. Our findings establish ALD-GaS as a technologically viable pathway for implementing anisotropic vdW materials in visible-spectrum photonics.
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All authors Aleksandr Slavich, Georgy Ermolaev, Dmitriy Grudinin, Mikhail Tatmyshevskiy, Alexander Syuy, Nikolay Pak, Dmitry Yakubovsky, Mikhail Mironov, Adilet Toksumakov, Alexander Melentev, Elena Zhukova, Anton Minnekhanov, Gleb Tselikov, Ivan Kruglov, Sergey M. Novikov, Andrey Vyshnevyy, Aleksey Arsenin, Valentyn Volkov

Quantum Gases

Thermal liquid-gas phase transition in a quasi-one-dimensional dipolar Fermi gas

Lanxuan Gao, Koki Takayama, Hiroyuki Tajima et al. (+2 more)

We theoretically investigate the thermodynamic properties of a quasi-one-dimensional single-component dipolar Fermi gas at finite temperatures. A self-bound fermionic droplet can be achieved by exchange correlations with long-range dipole-dipole interactions under quasi-one-dimensional confinement, where the interaction can be tuned by tilting the dipoles along the system coordinate. Using the Hartree-Fock approximation, we show how the liquid-gas phase transition occurs in this system and elucidate the finite-temperature phase structure consisting of a gas phase, liquid phase, gas-liquid coexistence phase, and spinodal phase. We also discuss its similarity to the liquid-gas phase transition in nuclear matter through a comparison with phenomenological models. By examining the experimental conditions for realizing self-bound fermionic droplets, we find that microwave-shielded fermionic polar molecules are promising candidates. Our results will be useful for an interdisciplinary understanding of self-bound fermionic matter as well as an analog quantum simulation of nuclear systems.
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All authors Lanxuan Gao, Koki Takayama, Hiroyuki Tajima, Takahiro M. Doi, Haozhao Liang

Materials Science

Auto-3DPFM: Automating Polarization-Vector Mapping at the Nanoscale

Ralph Bulanadi, Marti Checa, Michelle Wang et al. (+9 more)

The functional properties of ferroelectric materials are strongly influenced by ferroelectric polarization orientation; as such, access to consistent and precise characterization of polarization vectors is of substantial importance to ferroelectrics research. Here, we develop a fully automated three-dimensional piezoresponse force microscopy (Auto-3DPFM) technique automating all essential steps in interferometric PFM for 3D polarization vector characterization, including laser alignment, tip calibration and approach, image acquisition, polarization vector reconstruction, and visualization. The automation reduces the experimental burden of ferroelectric polarization vector characterization, while the back-and-forth calibration ensures consistency and reproducibility of 3D polarization reconstruction. An algorithmic workflow is also developed to identify domain walls and calculate their characteristic angles via a spatial vector-angle-difference method, presenting one unique capability enabled by Auto-3DPFM that is not accessible with traditional PFM techniques. Beyond representing a significant step forward in 3D polarization mapping, Auto-3DPFM promises to accelerate discovery via high-throughput and autonomous characterization in ferroelectric materials research. When integrated with machine learning and adaptive sampling strategies in self-driving labs, Auto-3DPFM will serve as a valuable tool for advancing ferroelectric physics and microelectronics development.
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All authors Ralph Bulanadi, Marti Checa, Michelle Wang, Franck Rothen, John Lasseter, Sumner B. Harris, Daniel Sando, Valanoor Nagarajan, Liam Collins, Stephen Jesse, Rama Vasudevan, Yongtao Liu

Materials Science · Cross-listed from physics.optics

Ionic Disorder-Mediated Exfoliation and Optical Birefringence in a Non-van der Waals Oxide

N. V. Pak, M. K. Tatmyshevskiy, I. A. Kruglov et al. (+11 more)

The landscape of two-dimensional photonics has been dominated by van der Waals (vdW) materials. Expanding this library to include non-vdW layered systems promises enhanced environmental robustness and access to novel functionalities, such as strong ionic conductivity, yet their exfoliation remains challenging. Here, we establish Na2Zn2TeO6 (NZTO), a P2-type superionic conductor, as an exfoliable non-vdW optical material. We demonstrate that the highly disordered, mobile Na+ interlayer inherently facilitates mechanical cleavage down to few-nanometer thicknesses (about 4 nm). Optical interrogation via spectroscopic ellipsometry reveals NZTO as a wide-bandgap dielectric with pronounced optical birefringence (Delta_n about 0.25) across the visible and near-infrared spectrum. The lattice dynamics, probed by temperature-resolved Raman spectroscopy, underscore the rigidity of the [Zn2TeO6]2- framework, which remains largely decoupled from the high ionic mobility. These results identify NZTO as a compelling platform for robust, anisotropic dielectric photonics, simultaneously opening a pathway toward the convergence of ionic transport and optical control - an emerging paradigm we term iono-photonics.
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All authors N. V. Pak, M. K. Tatmyshevskiy, I. A. Kruglov, K. V. Kravtsov, A. A. Minnekhanov, D. V. Grudinin, A. N. Toksumakov, A. S. Slavich, D. I. Yakubovsky, A. A. Vyshnevyy, M. A. El-Sayed, G. A. Ermolaev, A. V. Arsenin, V. S. Volkov

Materials Science

Predicting tunable nonreciprocal spin wave generation mediated by interfacial Dzyaloshinskii-Moriya interaction in magnonic heterostructures

Cameron A McEleney, Karen L Livesey, Robert E Camley et al. (+1 more)

Thin, metallic magnetic films can support nonreciprocal spin waves due to the interfacial Dzyaloshinskii-Moriya interaction (iDMI). However, these films typically have high damping, making spin wave propagation distances short (less than one micrometer). In this work, we theoretically study a thin ferromagnetic strip with iDMI and excite spin waves by driving a central segment of the strip. Spin waves propagate with different amplitudes to the left versus to the right from the driving region (i.e. nonreciprocity occurs) due to the iDMI. Our calculation based on spin-wave-dispersion plus our micromagnetic simulations both show that changing the driving segment width, driving frequency and static applied field strength tunes the nonreciprocity. Our calculation based on spin-wave-dispersion, using a so-called "overlap function" will allow researchers to predict conditions of maximum nonreciprocity, without the need for computational solvers. Moreover, to circumvent the issue of short propagation distances, we propose a geometry where iDMI is only present in the driving region and low-damping materials comprise the remainder of the strip. Our calculations show significant spin wave amplitudes over several microns from the excitation region.
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All authors Cameron A McEleney, Karen L Livesey, Robert E Camley, Rair Macêdo

Mesoscale and Nanoscale Physics

Creating and Deleting a Single Dipolar Skyrmion by Surface Spin Twists

Jin Tang, Jialiang Jiang, Yaodong Wu et al. (+8 more)

We report deterministic operations on single dipolar skyrmions confined in nanostructured cuboids using in-plane currents. We achieve highly reversible writing and deleting of skyrmions in the simple cuboid without any artificial defects or pinning sites. The current-induced creation of skyrmions is well-understood through the spin-transfer torque acting on surface spin twists of the spontaneous 3D ferromagnetic state, caused by the magnetic dipole-dipole interaction of the uniaxial Fe3Sn2 magnet with a low-quality factor. Current-induced deletions of skyrmions result from the combined effects of magnetic hysteresis and Joule thermal heating. Our results are replicated consistently through 3D micromagnetic simulations. Our approach offers a viable method for achieving reliable single-bit operations in skyrmionic devices for applications such as random-access memories.
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All authors Jin Tang, Jialiang Jiang, Yaodong Wu, Lingyao Kong, Yihao Wang, Junbo Li, Y. Soh, Yimin Xiong, Shouguo Wang, Mingliang Tian, Haifeng Du

Mesoscale and Nanoscale Physics

Current-controlled creations, deletions, and topological transformations of a single magnetic antiskyrmion in nanostructured cells

Yaodong Wu, Jialiang Jiang, Lingyao Kong et al. (+6 more)

Topological magnetic solitons have emerged as promising candidates for information carriers in spintronic devices, thanks to their fascinating electromagnetic properties. For fundamental device applications, the ability to electrically manipulate individual solitons is crucial. However, electrical manipulation of single antiskyrmions has been rarely demonstrated. In this work, we present current-controlled manipulations, encompassing the creation, deletion, and topological transformation of a single antiskyrmion within FeNiPdP nanostructured cells at room temperature. This nanostructure is uniquely designed with dimensions of about 400 nm in width and length, enabling the stabilization of a single antiskyrmion. By simply adjusting the density of nanosecond single-pulsed currents, we achieve the reversible creation and deletion of single antiskyrmions. Moreover, we uncover a rich variety of current-controlled topological transformations among individual antiskyrmions, skyrmions, bubbles, and ferromagnetic states. Our experimental findings are corroborated by micromagnetic simulations, highlighting the pivotal role of current-induced combined effects, such as spin transfer torque and Joule heating. Our results hold potential for advancing antiskyrmion-based device applications.
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All authors Yaodong Wu, Jialiang Jiang, Lingyao Kong, Wei Liu, Huanhuan Zhang, Shouguo Wang, Mingliang Tian, Haifeng Du, Jin Tang

Mesoscale and Nanoscale Physics

Skyrmion Sliding Switch in a 90-nm-Wide Nanostructured Chiral Magnet

Yaodong Wu, Jialiang Jiang, Weiwei Wang et al. (+5 more)

Magnetic skyrmions, renowned for their fascinating electromagnetic properties, hold potential for next-generation topological spintronic devices. Recent advancements have unveiled a rich tapestry of 3D topological magnetism. Nevertheless, the practical application of 3D topological magnetism in the development of topological spintronic devices remains a challenge. Here, we showcase the experimental utilization of 3D topological magnetism through the exploitation of skyrmion-edge attractive interactions in 90-nm-wide confined chiral FeGe and CoZnMn magnetic nanostructures. These attractive interactions result in two degenerate equilibrium positions, which can be naturally interpreted as binary bits for a skyrmion sliding switch. Our theory and simulation reveal current-driven spiral motions of skyrmions, governed by the anisotropic gradient of the potential landscape. Our experiments validate the theory that predicts a tunable threshold current density via magnetic field and temperature modulation of the energy barrier. Our results offer an approach for implementing universal on-off switch functions in 3D topological spintronic devices.
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All authors Yaodong Wu, Jialiang Jiang, Weiwei Wang, Lingyao Kong, Shouguo Wang, Mingliang Tian, Haifeng Du, Jin Tang

Materials Science

Trion Formation Hampers Single Quantum Dot Performance in Silane-Coated FAPbBr3 Quantum Dots

Jessica Kline, Shaoni Kar, Benjamin F. Hammel et al. (+8 more)

We explore silane-coated formamidinium lead bromide (FAPbBr3) quantum dots as single photon emitters and compare them to FAPbBr3 quantum dots passivated with a phosphoethylammonium derivative (PEAC8C12), which represents current state-of-the-art in zwitterionic molecular surface ligand passivation. We compare properties including single-photon purity (g2(t)), linewidth, blinking, and photostability. We find that at room temperature, these silane-coated dots perform comparably to the PEAC8C12 passivation in terms of single-photon performance metrics, while exhibiting improvements in photostability. However, we find that at 4K, silane-coated FAPbBr3 quantum dots perform worse than the PEAC8C12-passivated samples, exhibiting faster blue-shifting and photobleaching under illumination. Analysis of fluorescence lifetime intensity distributions from the photon-counting data indicates increased efficiency of fast non-radiative processes in the silane-coated quantum dots at 4K. We propose a trion related degradation pathway at low temperatures that is consistent with the observed kinetics and estimate that at 4K with 6.1 uJ/cm2, 472 nm excitation the silane-coated quantum dots build up double the trion population of their PEAC8C12-passivated counterparts.
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All authors Jessica Kline, Shaoni Kar, Benjamin F. Hammel, Yunping Huang, Zixu Huang, Seth R. Marder, Sadegh Yazdi, Gordana Dukovic, Bernard Wenger, Henry Snaith, David S. Ginger

Mesoscale and Nanoscale Physics

Symmetry-resolved magnetoelastoresistance in multivalley bismuth

Suguru Hosoi, Fumu Tachibana, Mai Sakaguchi et al. (+6 more)

We report a symmetry-resolved study of longitudinal magnetoelastoresistance (MER) in the multivalley material bismuth, with the current, uniaxial stress, and magnetic field all applied along the binary axis. The magnitude of MER exhibits a steep increase at low magnetic fields, reaches a peak, and then gradually decreases at higher fields. By decomposing the strain response into symmetric and antisymmetric symmetry channels, we reveal contrasting magnetic field dependencies. Despite the overall non-monotonic field dependence of the MER, the symmetric component remains nearly constant under magnetic fields, suggesting that the valleys in bismuth preserve a rigid-band nature against strain even in the presence of a magnetic field. In contrast, the antisymmetric component, associated with mobility anisotropy, dominates the MER response in a magnetic field. At low magnetic fields, the applied field effectively modifies the apparent mobility of each valley, leading to an enhancement in the magnitude of the antisymmetric MER. At higher fields, field-induced valley polarization further modifies this mobility anisotropy by altering the contributions from each valley's mobility, accounting for the moderate suppression of the MER. These findings demonstrate that symmetry-resolved MER serves as a powerful probe of valley-dependent electronic states and provides a fundamental platform for understanding the interplay between magnetic field, strain, and charge transport.
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All authors Suguru Hosoi, Fumu Tachibana, Mai Sakaguchi, Kentaro Ishida, Masaaki Shimozawa, Koichi Izawa, Yuki Fuseya, Yuto Kinoshita, Masashi Tokunaga

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

Activation of Polylactic Acid and Polycarbonate Surfaces with Non-Thermal Plasma

Jairo Rondón, Ginger Urrutia and Angel Gonzalez-Lizardo

Non-thermal plasma (NTP) surface activation has become a powerful and versatile strategy to engineer the interfacial properties of biomedical polymers whose intrinsic hydrophobicity limits their biological performance. In polymers such as polylactic acid (PLA) and polycarbonate (PC), NTP promotes the controlled incorporation of polar functional groups, increases surface energy, modifies dielectric behavior, and generates micro-roughness that collectively enhance protein adsorption and early cell adhesion. This review synthesizes and critically evaluates evidence across four complementary analytical pillars-contact-angle theory, dielectric impedance spectroscopy, FT-IR chemical mapping, and optical microscopy-to construct an integrated framework for interpreting plasma-induced chemical and morphological transformations. The convergence of multimodal results demonstrates that NTP consistently produces chemically active, polar, and moderately textured surfaces that support robust initial cell-material interactions. Furthermore, combining wettability, dielectric, and spectroscopic analysis enables the identification of activation pathways, the assessment of hydrophobic recovery dynamics, and the development of quantitative correlations between dielectric parameters and biological response. However, the literature also reveals key methodological gaps, including the limited use of unified multimodal protocols, insufficient evaluation of temporal stability, and a lack of predictive dielectric-biological models. By articulating these advances and limitations within a unified conceptual scheme, this review provides a roadmap for future research aimed at standardizing characterization workflows and enabling the rational design of next-generation plasma-functionalized biomaterials for tissue-engineering scaffolds, implantable devices, and advanced drug-delivery systems.
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Tuesday 9 December

Materials Science

AI-Driven Expansion and Application of the Alexandria Database

Théo Cavignac, Jonathan Schmidt, Pierre-Paul De Breuck et al. (+9 more)

We present a novel multi-stage workflow for computational materials discovery that achieves a 99% success rate in identifying compounds within 100 meV/atom of thermodynamic stability, with a threefold improvement over previous approaches. By combining the Matra-Genoa generative model, Orb-v2 universal machine learning interatomic potential, and ALIGNN graph neural network for energy prediction, we generated 119 million candidate structures and added 1.3 million DFT-validated compounds to the ALEXANDRIA database, including 74 thousand new stable materials. The expanded ALEXANDRIA database now contains 5.8 million structures with 175 thousand compounds on the convex hull. Predicted structural disorder rates (37-43%) match experimental databases, unlike other recent AI-generated datasets. Analysis reveals fundamental patterns in space group distributions, coordination environments, and phase stability networks, including sub-linear scaling of convex hull connectivity. We release the complete dataset, including sAlex25 with 14 million out-of-equilibrium structures containing forces and stresses for training universal force fields. We demonstrate that fine-tuning a GRACE model on this data improves benchmark accuracy. All data, models, and workflows are freely available under Creative Commons licenses.
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All authors Théo Cavignac, Jonathan Schmidt, Pierre-Paul De Breuck, Antoine Loew, Tiago F. T. Cerqueira, Hai-Chen Wang, Anton Bochkarev, Yury Lysogorskiy, Aldo H. Romero, Ralf Drautz, Silvana Botti, Miguel A. L. Marques

Mesoscale and Nanoscale Physics

Electronic structure of InP/ZnSe quantum dots: effect of tetrahedral shape, valence band coupling and excitonic interactions

Josep Planelles and Juan I. Climente

The energy levels and optical transitions of tetrahedral core/shell InP/ZnSe quantum dots (QDs) are investigated by means of multi-band k$\cdot$p theory. Despite the $\overline{T}_d$ symmetry relaxing spherical selection rules, the near-band-edge excitonic spectrum is reminiscent of that obtained for spherical nanocrystals. Exceptions appear in large (red-emitting) QDs, where transitions violating the (quasi-)angular momentum selection rule ($\Delta L=0,\pm 2$) are observed, and the ground state does not become dark ($P_{3/2}$-like). Valence band coupling is important in determining the symmetry, degeneracy and energy of hole states, with split-off holes playing a greater role than in CdSe QDs. The ($1S_e$-like) electron ground state exhibits moderate delocalization into the ZnSe shell. The confinement regime is then strong even for thick shells, which results in Coulomb interactions being mostly perturbative. Electrons remain largely localized in the InP core even in negative trions, despite electron-electron repulsions. At the same time, the asymmetry between Coulomb attractions and repulsions leads to negative (positive) trions being bound (antibound) by tens of meV. The biexciton binding energy switches from positive to negative, depending on the QD size.
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Soft Condensed Matter · Cross-listed from physics.bio-ph

Binding Kinetics Oppositely Regulates type II Topoisomerase Relaxation and Decatenation Activities

Cleis Battaglia, Filippo Conforto, Yair Augusto Gutierrez Fosado et al. (+4 more)

Type II Topoisomerases (topo II) are critical to simplify genome topology during transcription and replication. They identify topological problems and resolve them by passing a double-stranded DNA segment through a transient break in another segment. The precise mechanisms underpinning topo IIs ability to maintain a topologically simple genome are not fully understood. Here, we investigate how binding kinetics affects the resolution of two distinct forms of topological entanglement: decatenation and torsional relaxation. First, by single-molecule measurements, we quantify how monovalent cation concentration affects the dissociation rate of topo II from DNA. Second, we discover that increasing dissociation rates accelerate decatenation while slowing down relaxation catalytic activities. Finally, by using molecular dynamics simulations, we uncover that this opposite behaviour is due to a trade-off between search of target through facilitated diffusion and processivity of the enzyme in catenated versus supercoiled DNA. Thus, our findings reveal that a modulation of topo II binding kinetics can oppositely regulate its topological simplification activity, and in turn can have a significant impact in vivo.
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All authors Cleis Battaglia, Filippo Conforto, Yair Augusto Gutierrez Fosado, Matt Newton, Erin Cutts, Davide Michieletto, Antonio Valdes

Disordered Systems and Neural Networks

Transport scaling and critical tilt effects in disordered two-dimensional Dirac fermions

Swadeepan Nanda and Pavan Hosur

Two-dimensional (2D) Dirac fermions occur ubiquitously in condensed matter systems from topological phases to quantum critical points. Since the advent of topological semimetals, where the dispersion is often tilted around the band crossing where the Dirac fermion can appear, tilt has emerged as a key handle that controls physical properties. We study how tilt affects the transport and spectral properties of tilted 2D Dirac fermions under scalar disorder. Although our spectral analyses always show conformity to appropriate Gaussian ensembles, suggestive of delocalization, the conductivity scaling $g(L)$ shows a surprising richness. For a single Dirac node, relevant for quantum Hall transitions and topological insulator surface states, we find $g(L)\sim a_1\log(L)$ with a tilt-dependent coefficient $a_1>0$. Interestingly, when the tilt and transport directions are aligned, $a_1$ and hence $g(L)$ shows a spike at the critical point between the type-I and type-II regimes of the Dirac node. For systems with two Dirac nodes with unbroken time-reversal symmetry, pertinent to quasi-2D Dirac materials, we find $g(L)\sim L^{a_1}(\log L)^{a_2}$. However, we find a surprising tension between tilt along and perpendicular to the transport directions. For the former, $a_1$ changes sign as a function of tilt, hinting at a tilt-driven localization-delocalization transition, while $a_1<0$ for all tilts in the latter case, implying localization. These localized behaviors also reveal tension with the delocalization seen in spectral properties and suggest differing localization tendencies in real and Hilbert spaces. Overall, our work identifies tilt as an essential control parameter that uncovers rich and unconventional transport physics in 2D Dirac materials.
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Strongly Correlated Electrons

Spontaneous Symmetry Breaking in Chiral Current-Carrying High-Energy Eigenstates

Tigran A. Sedrakyan, Jun-Jun Pang, Chenan Wei et al. (+1 more)

Typical finite-energy-density eigenstates of nonintegrable systems are expected to obey the eigenstate thermalization hypothesis and to reproduce thermal local observables. In integrable systems, typical states are instead finite-entropy Bethe macrostates, or generalized Gibbs ensembles, with smooth quasiparticle occupations. Here we show that the spin-$\tfrac12$ XXX Heisenberg chain contains an exactly solvable exception. By biasing mutually commuting conserved charges, we use the ground state of a selector Hamiltonian to construct rare eigenstates of the undeformed XXX Hamiltonian. These states are atypical ordered, chiral, current-carrying, critical, zero-entropy Bethe macrostates at tunable XXX energy density. They lie outside the finite-entropy manifold dominating generalized Gibbs ensembles, yet remain exact XXX eigenstates with sharp Bethe occupations, finite scalar chirality, nonthermal local observables, and gapless Luttinger-liquid correlations. A finite-interval thermodynamic Bethe ansatz reveals an asymmetric chiral Bethe sea whose zero-field limit selects an extensive spin sector through $SU(2)$ symmetry breaking. A commuting exchange bias moves the same ordered macrostate through the full thermodynamic XXX energy band, including the Hilbert-space trace center. Finite-size DMRG and exact-diagonalization benchmarks indicate that the magnetochiral signatures persist under weak integrability breaking over prethermal time scales. The construction provides a controlled integrable realization of ETH-violating, scar-like large-deviation eigenstates and a route to ordered critical matter deep inside a many-body spectrum.
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All authors Tigran A. Sedrakyan, Jun-Jun Pang, Chenan Wei, Baigeng Wang

Superconductivity

Gate-Tunable Superconducting Spin Valve in a van der Waals Ferromagnet/Superconductor/Ferromagnet Trilayer

A. S. Ianovskaia, G. A. Bobkov, A. M. Bobkov et al. (+1 more)

We theoretically demonstrate a gate-tunable superconducting spin valve effect (SVE) in a van der Waals (vdW) heterostructure composed of a monolayer superconductor (S) sandwiched between two ferromagnetic (F) monolayers (F/S/F). By electrostatically gating the ferromagnetic layers to modulate their chemical potentials, the system can be continuously tuned between the standard, inverse and triplet (non-monotonic) SVE regimes within the same device. This tunability originates from the gate-controlled hybridization between the superconducting and ferromagnetic electronic spectra, which determines the effective exchange field induced in the S-layer. Furthermore, we reveal that gating enables exotic, non-BCS temperature dependencies of the superconducting order parameter, including reentrant superconductivity, bistable states, first-order phase transitions, and the emergence of superconductivity at finite temperatures. Our results establish vdW F/S/F trilayers as a versatile and highly controllable platform for superconducting spintronics, where external gate voltages can selectively activate different spin-valve functionalities and unconventional superconducting states.
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All authors A. S. Ianovskaia, G. A. Bobkov, A. M. Bobkov, I.V. Bobkova

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

Solvent-Directed Femtosecond Laser Ablation: Tuning Phase and Defect Engineering in Hybrid CdPS3/CdS Nanostructures

Andrei Ushkov, Nadezhda Belozerova, Gleb Tikhonowski et al. (+8 more)

The limited visible-light absorption of wide-bandgap van der Waals crystals fundamentally restricts their utility in solar energy conversion. Here, we report a surfactant-free, solvent-directed laser synthesis strategy to engineer the phase and optoelectronic properties of Cadmium Phosphorus Trisulfide (CdPS3). By exploiting the non-equilibrium thermodynamics of femtosecond pulsed laser ablation in liquid (fs-PLAL), we demonstrate a tunable transition from the stoichiometric ternary phase to a highly active binary-rich heterostructure. While ablation in water preserves the monoclinic CdPS3 lattice, the reducing environment of isopropanol triggers the formation of CdS quantum dots and metallic cadmium defect sites. This solvent-induced phase engineering transforms the ultraviolet-active host into a robust visible-light photocatalyst. The resulting hybrid CdPS3/CdS nanocolloids exhibit superior charge separation efficiency, driven by Schottky-like metal-semiconductor junctions, achieving ~ 90% degradation of Methylene Blue under 532 nm irradiation within 30 minutes. This work establishes fs-PLAL as a scalable defect-engineering tool for complex ternary layered materials, offering a new design of high-performance metal-thiophosphate-based photocatalysts.
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All authors Andrei Ushkov, Nadezhda Belozerova, Gleb Tikhonowski, Stepan Klimov, Alexander Syuy, Sergey V. Bazhenov, Sergey Novikov, Vladimir G. Leiman, Aleksey Arsenin, Gleb I. Tselikov, Valentyn Volkov

Materials Science · Cross-listed from cs.LG

Contrast transfer functions help quantify neural network out-of-distribution generalization in HRTEM

Luis Rangel DaCosta and Mary C. Scott

Neural networks, while effective for tackling many challenging scientific tasks, are not known to perform well out-of-distribution (OOD), i.e., within domains which differ from their training data. Understanding neural network OOD generalization is paramount to their successful deployment in experimental workflows, especially when ground-truth knowledge about the experiment is hard to establish or experimental conditions significantly vary. With inherent access to ground-truth information and fine-grained control of underlying distributions, simulation-based data curation facilitates precise investigation of OOD generalization behavior. Here, we probe generalization with respect to imaging conditions of neural network segmentation models for high-resolution transmission electron microscopy (HRTEM) imaging of nanoparticles, training and measuring the OOD generalization of over 12,000 neural networks using synthetic data generated via random structure sampling and multislice simulation. Using the HRTEM contrast transfer function, we further develop a framework to compare information content of HRTEM datasets and quantify OOD domain shifts. We demonstrate that neural network segmentation models enjoy significant performance stability, but will smoothly and predictably worsen as imaging conditions shift from the training distribution. Lastly, we consider limitations of our approach in explaining other OOD shifts, such as of the atomic structures, and discuss complementary techniques for understanding generalization in such settings.
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Materials Science

First-Principles Investigation of Mechanical, Lattice Dynamical, and Thermodynamic Properties of BaTiO3 Polymorphs

Arpon Chakraborty, M. N. H. Liton, M. S. I. Sarker et al. (+2 more)

BaTiO3 (BTO) is one of the most interesting classes of perovskite materials. The present study has been complied to explore some physical properties such as mechanical, vibrational, thermo-physical, and temperature dependent thermodynamic properties of BaTiO3 polymorphs comprehensively using first principles calculations based on density functional theory (DFT). All the polymorphs are found to be mechanically stable. The polymorphs are elastically anisotropic, machinable and have high hardness and toughness. The cubic phase possesses brittle nature while the other phases show ductile character. The high melting point of the polymorphs reveals that they can be used in tough situations. Also, three of the polymorphs can be used as thermal barrier coating. Moreover, we have also calculated the lattice dynamics and found improved results compared to the available results in the literature. In addition, the temperature and pressure dependent thermodynamic parameters of the polymorphs are evaluated and analyzed for the first time using the quasi-harmonic Debye model. The thermodynamic properties suggested that all phases would be good choices for application in the fields of automobiles, cooling systems, thermal electronic devices, thermal exchangers, and space crafts.
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All authors Arpon Chakraborty, M. N. H. Liton, M. S. I. Sarker, M. M. Rahman, M. K. R. Khan

Mesoscale and Nanoscale Physics

Orbital magnetization from parallel transport of Bloch states

Johannes Mitscherling, Jan Priessnitz and Libor Šmejkal

Quantum geometric formulations of linear and nonlinear responses can be constructed from a single building block in the form of a gauge-invariant interband transition operator. Here, we identify a second building block for quantum geometry: a band-resolved adiabatic connection operator that captures the noncommutativity between band projectors and their momentum derivatives. The band-resolved adiabatic connection operator, first introduced in the theory of adiabatic driving, serves as a generalized angular momentum within the state manifold of single bands, and we employ it to reformulate expressions for the band-resolved orbital magnetic moment. This form provides a complementary geometric interpretation alongside the multiband separation between energetic- and quantum-state properties by the two-state Berry curvature. Our formalism allows us to present formulas valid for both nondegenerate and degenerate bands, thereby removing the limitations of the common Bloch-state formula. We illustrate our theory by calculating a large orbital magnetization emerging without spin-orbit coupling in a spin-compensated, noncoplanar anomalous Hall magnet with degenerate bands.
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Mesoscale and Nanoscale Physics

On modeling quantum point contacts in quantum Hall systems

Prasoon Kumar and Kyrylo Snizhko

Quantum point contacts (QPC) are a key instrument in investigating the physics of edge excitations in the quantum Hall effect. However, at not-so-high bias voltage values, the predictions of the conventional point QPC model often deviate from the experimental data both in the integer and (more prominently) in the fractional quantum Hall regime. One of the possible explanations for such behaviors is the dependence of the tunneling between the edges on energy, an effect not present in the conventional model. Here we introduce two models that take QPC spatial extension into account: wide-QPC model that accounts for the distance along which the edges are in contact; long-QPC model accounts for the fact that the tunneling amplitude originates from a finite bulk gap and a finite distance between the two edges. We investigate the predictions of these two models in the integer quantum Hall regime for the energy dependence of the tunneling amplitude. We find that these two models predict opposite dependences: the amplitude decreasing or increasing away from the Fermi level. We thus elucidate the effect of the QPC geometry on the energy dependence of the tunneling amplitude and investigate its implications for transport observables.
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