Materials Science · Cross-listed from physics.chem-ph
Universal rapid machine learning models for predicting unconvoluted and convoluted X-ray Absorption Spectra
Fei Zhan and Zhi Geng
X-ray absorption near edge structure (XANES) is an essential tool for elucidating the atomic-scale, local three-dimensional (3D) structure of given materials and molecules. The rapid computation of XANES based on molecular 3D structures constitutes a vital element of quantitative XANES analysis. Here, we present an XANES prediction model. It takes 3D structures as input and generates either unconvoluted XANES or convoluted spectra as output, demonstrating excellent generalizability across diverse instrumental broadening. This model has validated its predictive capability for both hard X-ray XAS (exemplified by K-edges of 3d 4d metals and lanthanides) and soft X-ray XAS (using S K-edge as examples). Adopting the model, XANES spectra of multiple elements can be predicted using a single unified model. A highly efficient 3D structure fitting
algorithm based on this unconvoluted XANES prediction model, aiming to serve as an online data analysis method suitable for XAS beamlines.
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Statistical Mechanics · Cross-listed from quant-ph
Holstein Primakoff spin codes for local and collective noise
Sivaprasad Omanakuttan, Tyler Thurtell, Andrew K. Forbes et al. (+2 more)
Quantum error correction is essential for fault-tolerant
quantum computation, yet most existing codes rely on local control and stabilizer measurements that are difficult to implement in systems dominated by collective interactions. Inspired by
spin-GKP codes in PhysRevA.108.022428, we develop a general framework for Holstein-Primakoff
spin codes, which maps continuous-variable bosonic codes onto permutation-symmetric
spin ensembles via the Holstein-Primakoff approximation. We show that HP codes are robust to both collective and local-
spin noise and propose an explicit measurement-free local error recovery procedure to map local noise into correctable collective-
spin errors.
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All authors Sivaprasad Omanakuttan, Tyler Thurtell, Andrew K. Forbes, Vikas Buchemmavari, Ben Q. Baragiola
Materials Science · Cross-listed from eess.IV
In-situ On-demand Digital Image Correlation: A New Data-rich Characterization Paradigm for Deformation and Damage Development in Solids
Ravi Venkata Surya Sai Mogilisetti, Partha Pratim Das, Rassel Raihan et al. (+1 more)
Digital image correlation (DIC) has become one of the most popular methods for deformation characterization in experimental mechanics. DIC is based on optical images taken during experimentation and post-test image processing. Its advantages include the capability to capture full-field deformation in a non-contact manner, the robustness in characterizing excessive deformation induced by events such as yielding and cracking, and the versatility to integrate optical cameras with a variety of open-source and commercial codes. In this paper, we developed a new paradigm of DIC analysis by integrating camera control into the DIC process flow. The essential idea is to dynamically increase the camera imaging frame rate with excessive deformation or deformation rate, while maintaining a relatively low imaging frame rate with small and slow deformation. We refer to this new DIC paradigm as in-situ on-demand (ISOD) DIC. ISOD DIC enables real-time deformation analysis, visualization, and closed-loop camera control. ISOD DIC has captured approximately 178% more images than conventional DIC for samples undergoing crack growth due to its dynamically adjusted frame rate, with the potential to significantly enhance data richness for damage inspection without consuming excessive storage space and analysis time, thereby benefiting the characterization of intrinsic constitutive behaviors and damage mechanisms
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All authors Ravi Venkata Surya Sai Mogilisetti, Partha Pratim Das, Rassel Raihan, Shiyao Lin
Mesoscale and Nanoscale Physics
An expandable kinetic Monte Carlo platform for modelling electron transport through chiral molecules
Silvia Giménez-Santamarina, Andrés Mora Martínez, Gérliz M. Gutiérrez-Finol et al. (+1 more)
Chirality from molecular structures interacts with the
spin angular momentum of electrons and
photons giving rise to a variety of interesting phenomena. Among these, the observation of
spin selective transport at room temperature is particularly attractive for the development of functional spintronic devices. During the past twenty five years, two effects have attracted considerable experimental and theoretical
attention: electric Magnetochiral Anisotropy (eMChA) and Chirality Induced
Spin Selectivity (CISS). In spite of the large body of work devoted to these phenomena, there is still no clear agreement on their microscopic origin(s). It even remains an open question whether eMChA and CISS arise from fundamentally different mechanisms or whether they are different experimental manifestations of the same underlying microscopic effects. In this work, we have developed the core of an efficient kinetic Monte Carlo code for the modeling of electron transport under an applied voltage, where the alpha and beta
spin channels are treated independently. Each transport channel is characterized through its intrinsic electron mobility and an effective coupling between charge motion,
spin, and chirality. This framework makes it possible to quantify the
spin filtering that emerges from the interplay of these properties. From a set of simple rules emerges a voltage- and field-dependent effect that vanishes at low bias and shows the asymmetry between positive and negative voltages that is typically reported in electrical magnetochiral anisotropy experiments. We then move on to relate the internal parameters of our code with parameterization that has been used to describe the eMChA effect.
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All authors Silvia Giménez-Santamarina, Andrés Mora Martínez, Gérliz M. Gutiérrez-Finol, Alejandro Gaita-Ariño
Mesoscale and Nanoscale Physics
Erbium Probes of Magnetic Order in a Layered van der Waals Material
Guadalupe García-Arellano, Kang Xu, Arun Ramanathan et al. (+5 more)
There is growing interest in characterizing
magnetic order and dynamics in two-dimensional magnets, yet most efforts to date rely on external probes that interrogate the sample from tens of nanometers away and inevitably average over that length scale. Here we use internal,
lattice-embedded Er3+ defects in CrSBr as atomic-scale probes, accessing their telecom-band photoluminescence with spectroscopy and temperature-dependent confocal imaging to read out magnetism from within the material. At room temperature we observe narrow, long-lived photoluminescence (PL) lines in the telecom band, characteristic of erbium emitters. Upon cooling to 3 K and reheating, the Er3+ PL intensity and excited-state lifetime display pronounced thermal hysteresis with a minimum near 132 K, at the reported
antiferromagnetic (AFM) transition of CrSBr. Remarkably, we observe
magnetic signatures persisting over a broader temperature range than expected from bulk
benchmarks, suggesting nanoscale
magnetic order that locally survives beyond the nominal phase boundary. Further, a moderate in-plane field of 0.3 T shifts the PL minimum by +8 K, which we tentatively associate to field-biased
ferromagnetic correlations.
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All authors Guadalupe García-Arellano, Kang Xu, Arun Ramanathan, Jiayi Li, Gabriel I. López-Morales, Xavier Roy, Cyrus E. Dreyer, Carlos A. Meriles
Statistical Mechanics
A Local Structural Basis to Resolve Amorphous Ices
Quinn M. Gallagher, Ryan J. Szukalo, Nicolas Giovambattista et al. (+2 more)
Phases with distinct thermodynamic properties must differ in their underlying microscopic configurations. While ordered phases are readily distinguished by unit
cells and space groups, the local structural basis differentiating amorphous phases is less apparent. Here, using a new probabilistic data-driven framework applied to molecular simulations of water, we identify local collective variables that discriminate low-density and high-density amorphous (LDA and HDA) ices and characterize pressure-induced transitions between them. As expected, descriptors related to local density effectively distinguish LDA and HDA; however, phase identity is surprisingly encoded within the first coordination shell. Furthermore, the pressure-induced LDA–HDA transformation proceeds through redistribution between LDA- and HDA-like local environments with no evidence for intermediate structures, consistent with a first-order-like phase transition. This contrasts with the gradual structural
evolution observed in other amorphous systems, such as metallic glasses. Critically, local hydrogen density reveals pronounced structural hysteresis between compression and decompression pathways, which is not apparent in orientational order parameters, demonstrating that the microscopic interpretation of amorphous transformations depends fundamentally on descriptor choice. These findings are robust across force fields and provide a general strategy for characterizing disordered phases lacking obvious distinguishing features.
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All authors Quinn M. Gallagher, Ryan J. Szukalo, Nicolas Giovambattista, Pablo G. Debenedetti, Michael A. Webb
Materials Science
Non-monotonic roughness evolution in film growth on weakly interacting substrates
Dmitry Lapkin, Ismael S. S. Carrasco, Catherine Cruz Luukkonen et al. (+5 more)
Thin film deposition on weakly interacting substrates exhibits a unique growth mode characterized by initially strong island formation and rapidly increasing roughness, which reaches a maximum and subsequently decreases as the film returns to a smooth morphology. Here we show this rough-to-smooth growth mode experimentally for two molecular systems with substantially different geometries, namely, the effectively spherical buckminsterfullerene (C$_{60}$) and the disk-like 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN). This growth mode is explained by a geometrical model that captures the basic mechanisms of multilayer island growth, island coalescence, and formation of a continuous film. Additionally, kinetic Monte Carlo simulations with minimal ingredients demonstrate that this mode generally occurs for weakly interacting substrates, providing quantitative estimates of parameters that characterize adsorbate-adsorbate and adsorbate-substrate interactions. Both the model and simulations accurately describe the experimental data and highlight the generic nature of the phenomenon, independently of the details of the interactions and the molecular flux, which opens up a path for controlling nanoscale film roughness.
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All authors Dmitry Lapkin, Ismael S. S. Carrasco, Catherine Cruz Luukkonen, Oleg Konovalov, Alexander Hinderhofer, Frank Schreiber, Fábio D. A. Aarão Reis, Martin Oettel
Materials Science
Complex spin dynamics induced metamagnetic phase transitions in Dirac semimetal EuAuBi
Lipika, Shobha Singh, Anyesh Saraswati et al. (+8 more)
We report a comprehensive investigation of the physical properties of the Dirac semimetal compound EuAuBi single
crystals, using
neutron diffraction, magnetization, electrical transport, and specific heat measurements. EuAuBi crystallizes in a hexagonal structure with space group P63mc (No. 186). First-principles calculations using density functional theory characterize it as a Dirac semimetal, with a notable band-crossing in proximity to the
Fermi level (EF ) along the {\Gamma}-A direction. The
crystal exhibits three distinct
magnetic phases at 4 K (TN1), 3.5 K (TN2), and 2.8 K (TN3)as observed from
magnetic and specific heat measurements. However, zero-field
neutron diffraction resolves only two
magnetic phases: a commensurate
antiferromagnetic phase and a canted
antiferromagnetic phase. Field-dependent ac and dc magnetization measurements uncover field-induced non-trivial
spin textures in the
magnetic field range 1.5 to 3 T, manifested as a tilted plateau in the magnetization curves. The interplay between conduction carriers and these
spin textures is further evidenced by unique features in the
magnetic field-dependent longitudinal resistivity in the system. Finally, we present a comprehensive
magnetic phase diagram of EuAuBi, highlighting diverse
spin alignments present in the material. EuAuBi thus emerges as a rare material system in which both momentum-space and real-space Berry
curvature effects may coexist, providing a unique opportunity to investigate their interplay.
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All authors Lipika, Shobha Singh, Anyesh Saraswati, Vikas Chahar, Yan Sun, Pascal Manuel, Devashibhai Adroja, Walter Schnelle, Nitesh Kumar, Jhuma Sannigrahi, Kaustuv Manna
Mesoscale and Nanoscale Physics
Anisotropic Gyromagnetic Ratio and Orthogonal Einstein-de Haas Effect
Rui Xue, Zhenhua Qiao, Yang Gao et al. (+1 more)
We theoretically demonstrate an orthogonal Einstein-de Haas effect, where the rotation of
ferromagnetic materials is caused by the change of magnetization in the direction orthogonal to the rotation axis. This amounts to an anisotropic gyromagnetic ratio. To reveal its microscopic origin, we treat the
spin-orbit coupling as a perturbation, integrate out the electronic degree of freedom, and show that in collinear ferromagnets the
phonon angular momentum admits a dipolar structure in the
spin-order space due to the constraint of the
spin group
symmetry. The
spin-flipping and
spin-conserving parts of the
spin-orbit coupling contribute differently to such a dipolar structure. All these features are exemplified in a
lattice electron-
phonon model with
ferromagnetic order and $C_{1h}$ point group
symmetry. Our work lays the ground for revealing the connection between
phonon angular momentum and general
spin-order configurations.
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All authors Rui Xue, Zhenhua Qiao, Yang Gao, Qian Niu
Strongly Correlated Electrons
Emergent Random Spin Singlets in Disordered Spin-1/2 perovskite BaCu$_{1/3}$Ta$_{2/3}$O$_3$
Sagar Mahapatra, Francesco De Angelis, Dibyata Rout et al. (+8 more)
We investigate the disordered perovskite BaCu$_{1/3}$Ta$_{2/3}$O$_3$, where Cu (
spin-1/2) and Ta randomly occupy a pseudo-cubic
lattice. Synchrotron X-ray diffraction and X-ray absorption spectroscopy establish the local nature of the disorder, revealing the presence of structurally constrained
magnetic exchange paths. No
magnetic ordering or
spin freezing is observed down to 0.1 K. The low-temperature
magnetic and thermodynamic behavior is captured by a broad but non-singular distribution $P(J)$ of exchange couplings $J$. These results open the possibility of realizing a disordered
quantum ground state where the exchange randomness is broad yet intrinsically bounded, departing from the conventional infinite-randomness fixed point driven random-singlet phase.
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All authors Sagar Mahapatra, Francesco De Angelis, Dibyata Rout, Priyanshi Tiwari, Martin Etter, Edmund Welter, M. P. Saravanan, Rajeev Rawat, Satoshi Nishimoto, Carlo Meneghini, Surjeet Singh
Materials Science
Non-Enzymatic Glucose sensing properties of NiO nanostructured flower decorated Exfoliated Graphite Electrodes
Piyush Choudhary, Chhavi Chetiwal, Chandra Prakash et al. (+2 more)
Nanostructured transition metal
oxides (TMO) are extensively explored materials for non-enzymatic glucose sensors. TMOs such as Iron
oxides( {\alpha}-Fe2O3, {\gamma}-Fe2O3, Fe3O4, etc.), NiO, CuO, Cr2O3, etc. have been utilized as electrocatalysts for glucose determination. Tremendous efforts have been put into identifying the impact of different morphologies of these materials on the glucose-sensing performance. The larger surface area of the flower and wire-shaped catalysts make them better performing amongst other morphologies. Interestingly, it is important to note that most of such studies are on standard Glassy Carbon electrodes. Further to enhance the Electrochemically active surface area (ECSA) of the electrode, Carbon nanomaterials such as reduced
Graphene Oxide (r-GO) and Carbon Nanotubes (CNTs) are used as additives. Exfoliated Graphite paper electrodes offer better electrochemical characteristics than GCE electrodes due to their much larger ECSA. This study presents the non-enzymatic glucose sensing properties of NiO nanoflower-decorated Exfoliated Graphite electrodes. The amperometric detection of glucose shows a linear increase in current over a physiologically relevant wide range of 0-10 mM. The electrodes offer a better sensitivity of 304.12 microA per mM per cm square and a Limit Of Detection (LOD) of 100 microM. In addition, the electrodes showed high selectivity towards glucose in the presence of other interfering species such as Ascorbic acid, Fructose, Sucrose, and NaCl.
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All authors Piyush Choudhary, Chhavi Chetiwal, Chandra Prakash, Vijay K. Singh, Ambesh Dixit
Disordered Systems and Neural Networks
The dimensionality of the Hopfield model
Cristopher Erazo, Santiago Acevedo and Alessandro Ingrosso
We use the Binary Intrinsic Dimension (BID), a geometrical measure designed for binary data, to analyze the Hopfield model, a paradigmatic
spin system from statistical mechanics, machine learning and neuroscience. The BID allows us to characterize the phases and transitions of this system, and moreover it is robust against finite-size effects that interfere with the correct numerical estimation of the
spin-glass order parameter ($q$). We observe that the BID scales linearly with system size in the
retrieval and paramagnetic phases, where the correlations between
spins are small, and exhibits sublinear scaling in the whole
spin-glass phase, highlighting its correlated structure. Furthermore, we establish a direct relationship between the BID and the overlap distribution, unveiling a novel connection between the geometry of the state-space and standard
spin order parameters.
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Mesoscale and Nanoscale Physics
Tunable two-dimensional Dirac-Weyl semimetal phase induced by altermagnetism
Lizhou Liu, Qing-Feng Sun and Ying-Tao Zhang
We demonstrate a tunable Dirac-Weyl semimetal phase in two dimensions, realized by introducing in-plane d-wave altermagnetism into a Dirac system. This phase hosts both a central Dirac point and momentumseparated Weyl points connected by
Fermi line edge states. The Weyl point positions–and thus the edge-state connectivity–can be continuously tuned by rotating the altermagnetic axis. In contrast, out-of-plane altermagnetism gaps part of the bulk spectrum while preserving a single Dirac point accompanied by
chiral edge modes, as evidenced by quantized edge polarization. Our findings provide a tunable platform for manipulating Dirac-Weyl physics and topological edge transport in two dimensions.
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Statistical Mechanics · Cross-listed from quant-ph
Non-Markovian Decoherence Times in Finite-Memory Environments
Ramandeep Dewan
Decoherence is often modeled using Markovian master equations that predict exponential suppression of coherence and are frequently used as effective bounds on
quantum behavior in complex environments. Such descriptions, however, correspond to the singular physical limit of vanishing environmental
memory. Here we formulate decoherence using a general time-nonlocal decoherence functional determined solely by the environmental force correlation function, with Markovian dynamics recovered explicitly as a limiting case. For arbitrary stationary environments with finite temporal correlations, we show that the decoherence functional exhibits quadratic short-time growth that is model-independent within the finite-
memory class considered. Consequently, the decoherence time defined operationally-without assuming exponential decay-scales as the square root of the environmental correlation time, independent of the detailed form of the bath correlation kernel. These results are illustrated analytically for Gaussian-correlated, soft power-law, and Ornstein-Uhlenbeck environments. In the Ornstein-Uhlenbeck case, the non-Markovian dynamics admit an exact analytical closure, yielding a closed
evolution equation for the coherence. Exact numerical simulations based on a pseudomode mapping confirm the predicted scaling and show that exponential decoherence emerges only in the memoryless limit. Beyond coherence decay, we distinguish decoherence rates from observable loss of
quantum signatures by analyzing purity and von Neumann
entropy dynamics. We show that suppression of a specific coherence element need not coincide with irreversible
entropy production. Finally, we introduce an inferred-
memory perspective in which the environmental correlation time is treated as an operationally extractable parameter from dynamical data.
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Materials Science
Resistive-Switching Dynamics in Poly(3-hexylthiophene-2,5-diyl) Thin Films under Perforated Bottom Electrode
Sirsendu Ghosh and Pramod Kumar
The effect on the resistive switching (RS) mechanism in organic
semiconductor (OSC), Poly(3-hexylthiophene-2,5-diyl) (P3HT), due to the presence of the perforated bottom electrode (PBE) is investigated. The simulation shows a high local electric field at the edges of a patterned bottom electrode (BE), which can increase the probability of metal filament formation due to high current density, suggesting that the use of a PBE can assist the RS mechanism. RS involves switching from the high resistive state (HRS) to the low resistive state (LRS) known as the "SET" process at higher positive bias, and returning to HRS from LRS is known as the "RESET" process, which can be achieved at a negative bias. Various switching mechanisms are segregated from each other by the obtained current response to applied voltage. RS due to the formation of complete metal filaments between the top and bottom electrodes showed Ohm's law behaviour. On the other hand, a slope of approximately 2 in the log-log plot signifies that the space charge limited current (SCLC) dominates the device, and hence RS comes from incomplete metal filament formation or some changes in the P3HT
polymer itself. Similarly, high current density can transform the molecular arrangement from crystalline to an amorphous state due to joule heating, which leads to an intermediate OFF state. The high current density joule heating RS are from HRS to LRS, which is opposite to the metal filament based RS, hence it is called an inverted RS. The optical images of the fresh device and after multiple cycles indicate the metal percolation inside the OSC responsible for the RS. EDX spectrum at LRS in a cross-sectional transmission electron microscope (TEM) confirms the top metal percolation through the OSC and touches the BE. Therefore, the metal filament formation is the fundamental reason for these observed switching behaviours in P3HT.
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Materials Science
Catalog of phonon emergent particles and chiral phonons: Symmetry-based classification and materials database investigation
Houhao Wang, Dongze Fan, Hoi Chun Po et al. (+2 more)
Chirality and
topology are fundamental and ubiquitous in nature.
Symmetry has proven to be a powerful tool for predicting topological
phonons. However, to date, topological
phonon emergent particles (EMPs) have not been systematically cataloged in material databases. Moreover, traditional
symmetry methods are often inadequate for predicting
chiral phonons, because realistic calculations can yield negative results even when
symmetry analysis permits
phonon chirality. Here, we first establish a complete
symmetry-based classification: given any space group and Wyckoff positions (WYPOs) occupied by atoms, the number of occurrences of all (co-)irreducible representations ((co-)irreps) (that can host EMPs) can be unambiguously known without omission prior to expensive and parameter-dependent calculation. Moreover, whether a
phonon mode (belonging to one (co-)irrep) is
chiral can also be determined from the occupied WYPOs. We then perform a materials database investigation identifying over 25 million EMPs at high-
symmetry points and along high-
symmetry lines and computing the concrete value of
phonon angular momentum for each mode. We demonstrate two main applications: identifying ideal materials with surface chirality momentum locking and identifying materials with
giant phonon magnetic moment. All computational data are compiled into a website: http://
phonon.nju.edu.cn, which is expected to stimulate future studies on topological and
chiral phonons.
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All authors Houhao Wang, Dongze Fan, Hoi Chun Po, Xiangang Wan, Feng Tang
Other Condensed Matter · Cross-listed from physics.chem-ph
Quantum field theory approach for multistage chemical kinetics in liquids
Roman V. Li, Oleg A. Igoshin, Evgeny B. Krissinel et al. (+1 more)
Reaction-
diffusion processes play an important role in a variety of physical, chemical, and biological systems. Conventionally, the kinetics of these processes are described by the law of mass action. However, there are various cases where these equations are insufficient. A fundamental challenge lies in accurately accounting for the microscopic correlations that inevitably arise in bimolecular reactions. While approaches to describe microscopic correlations in many specific cases exist, no general theory for multistage reactions has been established. In this article, we apply the
quantum field theory approach to derive kinetic equations for general multistage reactive systems termed CMET (complete modified encounter theory). CMET can be formulated as a set of coupled partial differential equations that can be easily integrated numerically, thereby serving as a versatile tool for investigating reaction-
diffusion processes. Across multiple case studies, we demonstrated that CMET reproduces the kinetics predicted by many other theories within their respective scopes of applicability.
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All authors Roman V. Li, Oleg A. Igoshin, Evgeny B. Krissinel, Pavel A. Frantsuzov