Materials Science · Cross-listed from cs.RO
Functionalization of Situated Robots via Vapour
Kadri-Ann Pankratov, Leonid Zinatullin, Adele Metsniit et al. (+2 more)
Tight matching with the environment is key to effective
robot operation in complex settings. Situated
robots that build their bodies in situ (e.g. by spinning) are uniquely positioned to exploit their surroundings, yet functionalization of these structures remains an integration challenge - multimaterial spinning requires complex spinneret multiplexing, and mixture doping is limited by additive availability and chemical stability. We propose instead using materials available in the environment to functionalize in situ spun webs, reducing payload and uniquely matching the structure to its surroundings. As a demonstration, we transform an optically scattering PVDF fiber web into an optically absorbing, polypyrrole-grafted structure via pyrrole vapour exposure. Two activator-delivery strategies are shown:
liquid infusion into a prefabricated web, and activator pre-
embedding in the spinning mixture. Beyond this proof-of-concept, we foresee broader applications including biohybrid
robots that exploit bacterial genomes for specific biomolecule synthesis in situ.
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All authors Kadri-Ann Pankratov, Leonid Zinatullin, Adele Metsniit, Marie Vihmar, Indrek Must
Materials Science · Cross-listed from physics.ins-det
Methods for an Electron Emission Digital Twin
Salvador Barranco Carceles, Veronika Zadin, Steve Wells et al. (+3 more)
The effective design and operation of electron emitters is the core of critical technologies such as high-resolution electron imaging and spectroscopy or X-ray production for medical imaging. Despite 100 years of theoretical development in thermo- and field-electron emission models, the analysis of experimental data and design of electron emitters remains an art more than a science. This is due to the many processes that are involved in electron emission, which result in an extremely complex phenomenon. Here we describe and develop the Methods for an Electron Emission Digital Twin (MEEDiT), which integrates state-of-the-art thermo-field electron emission models and experimental data characterisation. By applying MEEDiT to silicon electron emitters, we demonstrate an approach that bridges the gap between simple experimental measurements and 'hidden' physical quantities like temperature and field enhancement. MEEDiT provides the physical consistency of a 3D simulation with the speed of a neural network, enabling resource-effective, real-time characterization and the extraction of critical data that is otherwise inaccessible during operation.
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All authors Salvador Barranco Carceles, Veronika Zadin, Steve Wells, Aquila Mavalankar, Ian Underwood, Anthony Ayari
Materials Science · Cross-listed from cond-mat.supr-con
Triplet superconductivity supported by an X$_9$ high-order Van Hove singularity
Chethan Sanjeevappa, Anirudh Chandrasekaran and Joseph J. Betouras
We study a four-fold symmetric dispersion relation of a
quantum material, which exhibits a single high-order Van Hove singularity of X$_9$ type at the
Fermi energy. First, we analyze in detail its form, type and density of states when the energy dispersion is in its canonical form. Subsequently, we study the possibility of a superconducting state when Hubbard repulsive interactions are taken into account. By solving the gap equation, it is shown that triplet state superconductivity with power-law dependence of the critical temperature T$_c$ on the interaction strength can be formed when a single singularity is present in the Brillouin zone. We discuss the effects of fluctuations and provide an upper bound of a possible superconducting critical temperature for the ruthenate Sr$_3$Ru$_2$O$_7$ which has been shown to exhibit this type of singularity.
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Materials Science · Cross-listed from cond-mat.supr-con
Probing Electromigration of Oxygen Vacancies in YBa$_2$Cu$_3$O$_{7-\delta}$ Devices by Multimodal X-ray Techniques
Caio C. Quaglio-Gomes, Stefan Marinković, Elijah A. Abbey et al. (+5 more)
Control of oxygen vacancies by electrical currents in complex
oxides such as YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) has attracted considerable interest due to the relative simplicity of its implementation and its potential for both fundamental studies and the tuning of superconducting device properties. However, the structural
evolution and depth-dependent effects associated with current-based techniques remain largely unexplored, particularly with respect to the connection between optical signatures and the spatial distribution of oxygen vacancies. Here, we combine nanoprobe X-ray Diffraction (NanoXRD), Cu K-edge X-ray Absorption Near-Edge Structure (XANES), X-ray Photoelectron Spectroscopy (XPS), electrical transport, and optical measurements to reveal modifications induced in YBCO microbridges by pulsed electromigration. We observe a c-axis expansion correlated with spectroscopic features of oxygen depletion in the Cu-O chains, and we confirm that oxygen redistribution, crystallographic changes, and copper coordination evolve consistently across techniques. Notably, the spatial profile of unit-
cell expansion closely follows the optical contrast observed after electromigration, demonstrating that the different signatures capture the same underlying oxygen reordering. We further show that optical microscopy cannot reliably capture bipolar electromigration involving strong resistance modifications, as surface deoxygenation appears largely irreversible. Taken together, our findings provide a significant step toward a microscopic understanding of current-assisted oxygen migration in YBCO and establish a framework for effectively exploiting vacancy control in high-temperature superconducting devices.
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All authors Caio C. Quaglio-Gomes, Stefan Marinković, Elijah A. Abbey, Davi A. D. Chaves, Anna Palau, Alejandro V. Silhanek, Pedro Schio, Maycon Motta
Materials Science
Generalized thermodynamic closure in ultrafast phonon dynamics
Sheng Qu, Jiyong Kim, Jaco J. Geuchies et al. (+9 more)
Driven-dissipative dynamics underlie a wide range of nonequilibrium phenomena in
quantum materials, yet reduced descriptions beyond the quasi-
equilibrium picture remain difficult to establish. Here, we experimentally demonstrate that a resonantly driven
phonon mode admits a generalized thermodynamic description in which coherence and energy jointly organize the nonequilibrium
evolution. Beyond a threshold driving field strength, we observe a delayed ultrafast response of a coherently driven
phonon mode. Combined with experimentally constrained Lindblad dynamics, we show that this delay reflects the finite-time spreading of excitations across many
phonon levels. At the same time, the full density-
matrix trajectories for three driving conditions collapse onto a common surface defined by energy and coherence. Our results establish a coherence-extended thermodynamic regime for driven
phonons and provide a framework for broader state engineering in driven-dissipative bosonic excitations.
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All authors Sheng Qu, Jiyong Kim, Jaco J. Geuchies, Sergey Kovalev, Jan-Christoph Deinert, Thales de Oliveira, Alexey Ponomaryov, Min Chen, Nilesh Awari, Igor Ilyakov, Mischa Bonn, Heejae Kim
Materials Science
Dynamical Simulation of On-axis Transmission Kikuchi and Spot Diffraction Patterns, Based on Accurate Diffraction Geometry Calibration
Tianbi Zhang, Raynald Gauvin, Aimo Winkelmann et al. (+1 more)
Transmission Kikuchi diffraction in the scanning electron microscope has gained popularity as a materials characterization technique for its high throughput and nanometer-level spatial resolution. While conventional diffraction pattern analysis routines focus on Kikuchi bands on the diffraction patterns, the full physical picture of electron scattering and diffraction pattern formation is more complex. Analysis that accounts for additional diffraction features such as diffraction spots and excess-deficiency effects should provide more robust and accurate indexing, if they can be incorporated in pattern indexing or simulation routines. A more accurate understanding of their physics of formation and geometry is required to enable this change. In this work, we demonstrate
geometric and full contrast dynamical simulation of on-axis transmission Kikuchi patterns, based on experimental patterns captured using a modular, direct electron detector-based set-up in the scanning electron microscope. First, a diffraction geometry calibration routine is proposed based on the electron channeling pattern of the direct electron detector. This allows us to accurately account for the position of diffraction spots in both
geometric and dynamical simulations with good agreement with experimental patterns. Further, by introducing appropriate weight factors, simulation of incoherent diffuse intensity, and calculation of the energy spectra of diffracted electrons, simulated patterns can be obtained which accurately capture the many diffraction features on experimental patterns. Workflows and findings of this work can be used to improve pattern indexing routines, as well as the understanding of the physical processes in the formation of on-axis transmission Kikuchi patterns.
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All authors Tianbi Zhang, Raynald Gauvin, Aimo Winkelmann, T. Ben Britton
Materials Science
Influence Functional Approach to Non-Perturbative Exciton Binding Renormalization from Phonons
Rohit Rana, Eric R. Heller, Antonios M. Alvertis et al. (+2 more)
We construct a many-body model
Hamiltonian to capture how
phonons renormalize
exciton binding as a function of temperature. By using the GW approximation and density functional perturbation theory, we are able to parameterize this
Hamiltonian completely from first principles. To capture static quasiparticle properties non-perturbatively, we evolve this
Hamiltonian in imaginary time with path integral Monte Carlo using an influence functional based approach. For a class of Wannier-Mott type
excitons, our binding energies are in quantitative agreement with experiment. We find that in addition to long-range dipolar interactions from longitudinal optical modes, short-ranged deformation potentials from acoustic modes and transverse optical modes can significantly renormalize electron and hole polaron binding energies at elevated temperature. However,
exciton binding energies are only appreciably renormalized by coupling to optical
phonons.
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All authors Rohit Rana, Eric R. Heller, Antonios M. Alvertis, Jeffrey B. Neaton, David T. Limmer
Materials Science
Origin of the tetragonal-to-hexagonal phase transitions in Fe-doped BaTiO$_3$
Zhiyuan Li, Ruiwen Xie and Hongbin Zhang
Based on detailed first-principles calculations, we investigate the tetragonal-to-hexagonal phase transition in Fe-doped BaTiO$_3$. Free energy calculations confirm a crossover from the tetragonal to hexagonal phases at 2.7–6% Fe on cooling from the sintering temperature, in agreement with experimental observations, where comparative calculations show that neither CaTiO$_3$ nor SrTiO$_3$ exhibits similar behavior under equivalent substitution. Furthermore, three possible mechanisms are quantified: oxygen vacancies shift the crossover concentration from 2.7–6% to 1.1–4.7%, Jahn-Teller distortions are confined to the tetragonal phase, both favoring tetragonal-to-hexagonal phase transitions; whereas the tolerance factor is reduced in comparison with that of pristine BaTiO$_3$ for reasonable Fe valence states, disfavoring the occurrence of the hexagonal phases. Detailed analysis on the electronic structure reveals that the charge redistribution induced by oxygen vacancy is strongly orbital dependent, the added charge entering the $d_{z^2}$ orbital.
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Materials Science
LPC3D: An Enhanced Parallel Software for Large-Scale Simulation of Adsorption in Porous Carbons and Supercapacitors
El Hassane Lahrar, Mathieu Salanne, Rudolf Weeber et al. (+1 more)
Simulations of electrochemical double layer capacitors based on porous carbon electrodes, energy storage systems which accumulate and release energy through reversible ion adsorption at electrode/electrolyte interfaces, are often performed at the microscopic scale, using molecular dynamics. Such simulations provide crucial information to understand the adsorption of ions and the effect of confinement on some electrochemical properties. However, their computational cost limits the size of the systems studied to a few nanometers and a few pores while experimental materials are highly heterogeneous with a distribution of particle and pore sizes. LPC3D is a software designed for mesoscopic simulations of porous carbon particles and carbon-based supercapacitors which allow for the inclusion of such heterogeneity. The code calculates quantities of adsorbed ions,
diffusion coefficients and NMR spectra of ions / molecules adsorbed in porous carbon
matrices. In this work, we report on a new implementation of LPC3D, written in Python using the PyStencils module which can generate optimized C++ and CUDA code. This implementation is parallel, can be run on CPU and GPU, and allows one to simulate systems going from a single carbon particle to a supercapacitor with hundreds of micrometers in length. Here, we apply the new implementation of LPC3D to the simulation of supercapacitors with porous carbon electrodes represented as monoliths or carbon films to investigate the influence of the microstructure on the resulting adsorption and spectroscopic properties.
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All authors El Hassane Lahrar, Mathieu Salanne, Rudolf Weeber, Céline Merlet
Materials Science · Cross-listed from quant-ph
Development of Biphoton Entangled Light Spectroscopy (BELS) using Bell pairs
V. V. Desai and N. P. Armitage
We introduce Biphoton
Entanglement Light Spectroscopy (BELS), a
quantum spectroscopic technique that employs polarization entangled Bell pairs and two
photon interference to probe material properties. In BELS, the measured signal arises not from single
photon intensities but from changes in the joint polarization and path correlations of biphoton Bell pairs transmitted through or scattered by a sample and analyzed via cross channel coincidences. A key concept of BELS is the explicit mapping between Jones
matrix operations and transformations within the Bell state
manifold. Optical elements that are equivalent under classical polarization optics can produce qualitatively distinct signatures in the coincidence landscape when interrogated with entangled
photons. We demonstrate that linear birefringence and Faraday rotation generate orthogonal admixtures of Bell states, yielding experimentally distinguishable coincidence channels within a single measurement. We measure birefringence in an anisotropic dielectric and Faraday rotation in $\text{Tb}_3\text{Ga}_5\text{O}_{12}$. By mapping the changes to the photonic
entanglement, BELS establishes a new framework for future
entanglement enhanced spectroscopy, a potentially powerful approach in characterizing
quantum materials, nanophotonic devices, and light matter interactions perhaps eventually at a fundamentally
quantum level.
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Materials Science
AI-supported Degradation Study of Carbon-based Perovskite Solar Cells: Learning the Device Physics of Perovskite Solar Cells: A Drift-Diffusion Guided Autoencoder Approach
Oliver Zbinden, Sharun Parayil Shaji and Wolfgang Tress
Carbon-electrode-based PSC devices are stressed under 1 Sun equivalent illumination in a stability setup, and different scan-speed dependent current-voltage (J-V) curves are measured during aging. The collected data is used to estimate several physical parameters that contain information about charge transport and recombination using Machine Learning (ML), which allows for in situ tracking of possible signs of degradation. These results are compared to what can be classically interpreted by analysing changes in J-V curves, and the
evolution of the predicted parameters is studied. The predictions are then used to simulate a digital twin of the measured devices, and their physical implications and the differences between measurements and devices are discussed.
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Materials Science
Chirality Cannot Be Ferroic in Enantiomorphic Space-Groups
F. Gómez-Ortiz, S. Mamoudou Taganga, E. E. McCabe et al. (+2 more)
With growing interest in structural chirality in periodic solids, it has been suggested that chirality might constitute a new ferroic order parameter. In this work, we demonstrate, by means of a formal group-theoretical proof and a systematic group-subgroup analysis, that achiral-to-
chiral transitions that produce either member of an enantiomorphic pair cannot be driven by a Brillouin-zone-center ($\Gamma$-point) instability from a common achiral parent. We further substantiate this result by explicitly showing that none of the achiral parent space groups that admit
symmetry-
chiral phonon eigenvectors host them at the zone center. Given that a primary ferroic order parameter must, among other requirements, transform according to a zone-center irreducible representation, we conclude that phase transitions leading to enantiomorphic space groups cannot be classified as primary ferroic transitions. This predicts that any critical enhancement of fluctuations must occur at finite-$q$ rather than as a divergence of a uniform macroscopic susceptibility.
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All authors F. Gómez-Ortiz, S. Mamoudou Taganga, E. E. McCabe, A. H. Romero, E. Bousquet
Materials Science
Electrochemical and thermal control of continuous phase transitions in P2-NaxNi1/3Mn2/3O2
Dylan A. Edelman, John Cattermull, Jue Liu et al. (+7 more)
Sodium layered
oxides often undergo phase transformations involving ordering or disordering of Na+ upon desodiation, i.e., when cycled as a battery electrode. Accurately characterizing these phases is crucial for understanding functional properties, such as chemical diffusivity. In this work, we reveal that Na+-vacancy (dis)ordering in a layered
oxide is intrinsically coupled to
symmetry-changing phase transformations of the host structure. We examine the low-
symmetry orthorhombic unit
cell of P2-NaxNi1/3Mn2/3O2 (NNM) using both
neutron and X-ray diffraction. Specifically, special sodium stoichiometries (x = 2/3 and 1/2) exhibit concomitant Na+-vacancy ordering and an orthorhombic distortion from the parent hexagonal unit
cell. We then demonstrate that electrochemical desodiation drives
symmetry-changing transformations in NNM that are linked to Na+-vacancy (dis)ordering, with evidence of second-order behavior observed near x = 2/3. Variable-temperature synchrotron X-ray diffraction further clarifies the coupling between Na+-vacancy disordering and orthorhombic-to-hexagonal phase transitions in NNM. Surprisingly, the temperature-driven phase transitions at x = 2/3 and 1/2 differ in character, appearing second-order and first-order, respectively. Our analysis of the phase transitions in NNM has fundamental consequences for sodium chemical diffusivity in the vicinity of the ordered phases and leads to design principles for modifying phase transition behavior in the broader class of intercalation electrodes.
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All authors Dylan A. Edelman, John Cattermull, Jue Liu, Zhelong Jiang, Hari Ramachandran, Edward Mu, Cheng Li, Anton Van der Ven, Katherine J. Harmon, William C. Chueh
Materials Science · Cross-listed from quant-ph
Dicke materials as a resource for quantum squeezing
Vaibhav Sharma, Shung-An Koh, Jonathan Stepp et al. (+8 more)
We study
magnetic materials whose low energy physics can be effectively described by a Dicke model, which we term Dicke materials. We show how a Dicke model emerges in such materials due to a coexistence of fast-dispersing and slow-dispersing
spins, which are strongly coupled. Analogous to the paradigmatic Dicke model describing light-matter interactions, these materials also exhibit signatures of a superradiant phase transition. The ground state near the superradiant phase transition is expected to be squeezed, making Dicke materials a resource for
quantum metrology and witnessing
entanglement in solid-state systems. However, as an
entanglement measure, squeezing can be sensitive to perturbations that are otherwise irrelevant for usual correlation functions and order parameters. Motivated by the prospect of observing squeezing in such Dicke materials, we study the robustness of ground state squeezing under ubiquitous imperfections such as finite temperature, disorder, and local interactions. Using analytical and numerical techniques, we show that the squeezing obtained is perturbatively stable against these imperfections and quantitatively evaluate regimes promising for experimental observation.
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All authors Vaibhav Sharma, Shung-An Koh, Jonathan Stepp, Dasom Kim, Takumu Obata, Yuki Saito, Motoaki Bamba, Han Pu, Hanyu Zhu, Junichiro Kono, Kaden R. A. Hazzard
Materials Science
A family tree for hafnia
Nicolaie Cernov, Jorge Íñiguez-González and Hugo Aramberri
Several candidate reference phases have been proposed to discuss phase transitions and ferroelectricity in hafnia in recent years. Although these proposals comply with crystallographic requirements, a physically compelling rationale connecting parent and daughter phases is often lacking. This problem is aggravated by the absence of clearly dominant polarization switching pathways, making it difficult to formulate a robust physical criterion for identifying the relevant high-
symmetry states. Here we use first-principles calculations to show that pressure provides a simple and robust criterion for establishing physically meaningful family relationships among many hafnia polymorphs, including the monoclinic ground state and the technologically relevant ferroelectric phase, and their respective parent structures. Our simulations also reveal several previously unreported phases, including higher-energy structures that act as common ancestors of the widely discussed cubic and orthorhombic reference phases.
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Materials Science
Characterizing High-Capacity Janus Aminobenzene-Graphene Anode for Sodium-Ion Batteries with Machine Learning
Claudia Islas-Vargas, L. Ricardo Montoya, Carlos A. Vital-José et al. (+3 more)
Sodium-ion batteries require anodes that combine high capacity, low operating voltage, fast Na-ion transport, and mechanical stability, which conventional anodes struggle to deliver. Here, we use the SpookyNet machine-learning force field (MLFF) together with all-electron density-functional theory calculations to characterize Na storage in aminobenzene-functionalized Janus
graphene (Na$_x$AB) at room-temperature. Simulations across state of charge reveal a three-stage storage mechanism-site-specific adsorption at aminobenzene groups and Na$_n$@AB$_m$ structure formation, followed by interlayer gallery filling-contrasting the multi-stage pore-, graphite-interlayer-, and defect-controlled behavior in hard carbon. This leads to an OCV profile with an extended low-voltage plateau of 0.15 V vs. Na/Na$^{+}$, an estimated gravimetric capacity of $\sim$400 mAh g$^{-1}$, negligible volume change, and Na diffusivities of $\sim10^{-6}$ cm$^{2}$ s$^{-1}$, two to three orders of magnitude higher than in hard carbon. Our results establish Janus aminobenzene-
graphene as a promising, structurally defined high-capacity Na-ion anode and illustrate the power of MLFF-based simulations for characterizing electrode materials.
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All authors Claudia Islas-Vargas, L. Ricardo Montoya, Carlos A. Vital-José, Oliver T. Unke, Klaus-Robert Müller, Huziel E. Sauceda
Materials Science · Cross-listed from cond-mat.mes-hall
Supercurrent-Driven Néel Torque in Superconductor/Altermagnet Hybrids
Hamed Vakili, Moaz Ali, Igor Žutić et al. (+1 more)
We predict a supercurrent-driven Néel
spin-orbit torque in a
superconductor/$d$-wave altermagnet
heterostructure, associated with the emergence of
spin-triplet correlations. The effect can be understood as a consequence of the supercurrent-induced
spin polarization, owing to the interplay between
spin orbit coupling and momentum-dependent
spin splitting, as found, for example, in altermagnets. Remarkably, the supercurrent can be tuned by the Néel-vector direction, and the supercurrent-induced torque can both propel
magnetic domain walls and reverse the Néel-vector orientation within a domain wall. These findings establish
superconductor/altermagnet
heterostructures as a versatile platform for the {supercurrent-driven} control of the Néel vector, with potential applications in racetrack
memory, dissipationless superconducting electronics, and unconventional computing.
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All authors Hamed Vakili, Moaz Ali, Igor Žutić, Alexey A. Kovalev
Materials Science
Universal inverse-cube thickness scaling of projectile penetration energy in ultrathin films
Alessio Zaccone and Tim W. Sirk
Ultrathin films of widely different materials exhibit a dramatic enhancement of projectile penetration resistance under high–velocity impact. Despite extensive simulations and experiments, a unifying physical explanation has remained elusive. Here we show that the thickness dependence of the specific penetration energy obeys a universal law, $E_p^*(h)=E_{p,\infty}^*+B h^{-3}$, independent of chemical composition and degree of disorder. The inverse–cube scaling is traced back to a finite–size correction to the effective shear modulus arising from the suppression of long–wavelength nonaffine deformation modes in confined solids. The scaling quantitatively describes impact data for multilayer
graphene,
graphene oxide, and
polymer thin films, revealing a common elastic origin for nanoscale impact resistance.
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Materials Science
Crystallographic Orientation-Dependent Magnetotransport in the Layered Antiferromagnet – CrSBr
Naresh Shyaga, Pankaj Bhardwaj, Rajib Sarkar et al. (+3 more)
Among two-dimensional
magnetic materials, CrSBr has attracted considerable
attention owing to its coexistence of
ferromagnetic and
antiferromagnetic ordering, which depends sensitively on crystallographic orientation. An additional distinguishing feature of CrSBr is its highly anisotropic
Fermi surface in momentum space. In this work, we present a comprehensive investigation of magnetoresistance by systematically orienting the bias current and the applied
magnetic field along all three crystallographic axes. We demonstrate that the magnetoresistance serves as a direct probe of electronic anisotropy, exhibiting pronounced variations when the current is applied along different crystallographic directions under a
magnetic field perpendicular to the sample plane. For in-plane
magnetic fields, we observe conventional anisotropic magnetoresistance accompanied by hysteresis, indicative of
ferromagnetic behavior. Overall, our study provides a complete picture of electronic transport in CrSBr as a function of bias current and
magnetic field orientation with respect to crystallographic directions, thereby opening pathways for future experiments requiring high sensitivity of electrical resistance to
magnetic field gradients.
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All authors Naresh Shyaga, Pankaj Bhardwaj, Rajib Sarkar, Jagadish Rajendran, Abhiram Soori, Dhavala Suri
Materials Science
Decoupling Precipitation and Surface Complexation during Mn(II) Removal by Biochar via Experiments and Atomistic Simulations
Audrey Ngambia, Anastasiia Gavrilova, Haitao Huang et al. (+4 more)
Manganese(II) mobilised by mining activity poses a persistent water-quality challenge, yet the mechanisms by which low-cost sorbents, such as biochar, sequester Mn(II) remain poorly resolved. This study identifies the specific chemical drivers of Mn(II) sequestration by combining fixed-bed column and batch experiments with atomistic molecular dynamics simulations. Oilseed rape straw biochars, produced at 350\textdegree C, 550\textdegree C, and 700\textdegree C, removed 20-50% of dissolved Mn from acidic influent (pH 4, 5 ppm). High-temperature biochar achieved the greatest removal ($\sim$50%) and rapidly increased effluent pH to 9, triggering alkaline precipitation. Conversely, lower-temperature biochars removed 20-30% of Mn while maintaining a near-neutral pH (7-7.5). Enhanced \ce{K+} release in these systems indicates significant cation exchange and non-precipitative pathways. Molecular simulations confirmed that while neutral surfaces show weak Mn(II) association, deprotonated sites drive strong adsorption through inner-sphere complexation ($\sim$50% removal) and outer-sphere association ($\sim$10%). These results establish a mechanistic framework to distinguish between precipitation-led and surface-complexation-led removal. By providing specific chemical criteria for Mn-targeted sequestration, this work enables the rational design of engineered biochars for sustainable water remediation.
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All authors Audrey Ngambia, Anastasiia Gavrilova, Haitao Huang, Zhuodong Lyu, Ondřej Mašek, Margaret Graham, Valentina Erastova
Materials Science
Adsorption energies and decomposition barrier heights for ethylene carbonate on the surface of lithium from cluster-based quantum chemistry
Ethan A. Vo, Hung T. Vuong, Zachary K. Goldsmith et al. (+7 more)
For ethylene carbonate on the (100) surface of lithium, we calculate the adsorption energy in two binding motifs as well as the barrier height for a ring-opening decomposition reaction. We validate a scheme for producing results in the thermodynamic limit by correcting results obtained on finite lithium clusters containing only 40-100 atoms, which enables the use of hybrid density functionals, the random-phase approximation, and correlated wavefunction theories such as coupled-cluster theory and auxiliary-field
quantum Monte Carlo. We find that the high-level theories agree to within 2-5 kcal/mol and can therefore serve as
benchmarks for more affordable methods. Using our reference data, we demonstrate that generalized gradient approximation functionals, such as PBE, are not sufficiently accurate for reaction barrier heights, and we identify $\omega$B97X-V as an especially promising functional for the interfacial chemistry of electrolyte solvents at lithium metal anodes.
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All authors Ethan A. Vo, Hung T. Vuong, Zachary K. Goldsmith, Hong-Zhou Ye, Yujing Wei, Sohang Kundu, Ardavan Farahvash, Garvit Agarwal, Richard A. Friesner, Timothy C. Berkelbach
Materials Science
Interlayer coupling driven stabilization and superconductivity in bilayer CoTe$_2$
Wenping Chen, Ziyun Zhang and Feipeng Zheng
Interlayer coupling plays a critical role in van der Waals materials by governing
lattice stability and emergent
quantum phases, yet its impact on few-layer hexagonal CoTe$_2$ remains unclear. Here, using first-principles calculations, we systematically investigate monolayer and
bilayer CoTe$_2$ with an emphasis on their electronic structures,
lattice dynamics, and electron-
phonon coupling, and elucidate the underlying mechanisms driven by interlayer interactions. Our results show that monolayer CoTe$_2$ exhibits pronounced dynamical instability at low temperatures, whereas interlayer coupling stabilizes the
bilayer crystal structure and gives rise to
phonon-mediated superconductivity with a predicted critical temperature of about $4.7$~K when
spin-orbit coupling is included. The stabilization and superconductivity in
bilayer CoTe$_2$ are primarily attributed to interlayer-coupling-induced Te-$p_z$ charge redistribution and the associated modification of the
Fermi surface and electron-
phonon coupling. Finally, we discuss how
spin-orbit coupling in
bilayer CoTe$_2$ weakens the EPC and superconductivity. Our work clarifies how interlayer coupling can jointly tune structural stability and superconductivity in few-layer CoTe$_2$, providing insights for engineering
quantum phases in layered transition-metal dichalcogenides.
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Materials Science · Cross-listed from physics.optics
Ultra-high THz-field-confinement at LaAlO3 twin walls
Jakob Wetzel, Javier Taboada-Gutiérrez, Matthias Roeper et al. (+13 more)
The control and steering of light at nanometre length scales is crucial for the development of both fundamental science and nanophotonic technologies. Recent advancements have been achieved by exploiting various crystalline anisotropies, allowing for subdiffractional and diffraction-less canalisation of energy. These studies in particular benefit from stacking and twisting of 2D materials, whereas corresponding capabilities of anisotropic bulk
crystals are rather unexplored. In this work, we show that ferroelastic twin walls - crystallographically perfect 2D-sheets that separate regions of differently oriented domains - in the distorted perovskite LaAlO3 provide a natural platform for broadband lateral confinement and superb canalisation of light at the nanoscale. Without fabrication processes, the electromagnetic fields localised at such walls exhibit lateral optical sizes up to 260 times smaller than the free-space wavelength. Depending on the adjacent domain orientation and frequency, the twin wall pattern preferentially concentrates or repels the electromagnetic energy, constituting a natural building block towards broadband MIR and THz nanophotonics for polaritonic circuitry.
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All authors Jakob Wetzel, Javier Taboada-Gutiérrez, Matthias Roeper, Felix G. Kaps, Giuliano Esposito, Drini Marchese, Robin Buschbeck, Pauline Lenz, J. Michael Klopf, Hans A. Bechtel, Stephanie N. Gilbert Corder, Jeremie Teyssier, Susanne C. Kehr, Lukas M. Eng, Alexey B. Kuzmenko, Samuel D. Seddon
Materials Science
In-plane and out-of-plane electric dipoles and phase transitions in 2D-layered TlGaS2
A. D. Molchanova, L. H. Yin, L. P. Gao et al. (+4 more)
Out-of-plane and in-plane electric polarization, which rarely coexist in a two-dimensional (2D) ferroelectric material, offer different advantages in ferroelectricity-based devices. Here, we report the coexistence of in-plane and out-of-plane electric dipoles, along with various phase transitions, in 2D van der Waals layered TlGaS2 single
crystal.
Quantum paraelectricity was observed along both in-plane and out-of-plane directions of the TlGaS2
crystal. Detailed investigation of the
quantum paraelectric soft-mode behavior reveals a close correlation between the electric dipoles and the off-center displacement of Tl1+ ions with 6s2 lone pairs in TlGaS2. Anomalies near temperatures of about 120 K and 60-75 K in dielectric and/or infrared spectra indicate the existence of local or weak long-range structural transitions in TlGaS2. Our results provide important experimental evidence for elucidating the phase transitions and coexistence of in-plane and out-of-plane electric dipoles in 2D layered TlGaS2.
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All authors A. D. Molchanova, L. H. Yin, L. P. Gao, W. H. Song, Y. P. Sun, K. R. Allahverdiyev, M. N. Popova
Materials Science
Visualizing spin-polarization of an altermagnet KV$_2$Se$_2$O via spin-selective tunneling
Guofei Yang, Chuang Li, Chengwei Wang et al. (+16 more)
Altermagnetism, a recently identified
magnetic phase that combines vanishing net magnetization with momentum-dependent
spin splitting, challenges the conventional dichotomy between ferromagnets and antiferromagnets. While several candidate materials have been proposed, direct experimental evidence linking
crystal symmetry, electronic structure and d-wave
spin polarization remains scarce. Here we report the visualization of a metallic d-wave altermagnet in KV2Se2O. Through
spin-selective scanning tunneling microscopy powered by a topological
insulator tip, we uncover
symmetry-protected momentum-dependent
spin splitting that follows a characteristic d-wave form factor. Our results establish KV2Se2O as a tunable platform to study the interplay between
spin-valley locking,
Fermi-surface instability and unconventional magnetism, and open a pathway toward
symmetry-engineered spintronics without net magnetization.
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All authors Guofei Yang, Chuang Li, Chengwei Wang, Xudong Zhao, Yifan Wan, Hengrui Gui, Guoqing Zeng, Saizheng Cao, Chuqiao Hu, Qihe Yu, Yujia Zhang, Dong Chen, Yu Liu, Yu Song, Yongjun Zhang, Fei Liu, Lun-Hui Hu, Lin Jiao, Huiqiu Yuan