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Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Saturday 11 October

Materials Science

Atomic bonding in equilibrium single-component melts. The cases of arsenic, antimony and bismuth

Artem A. Tsygankov, Bulat N. Galimzyanov and Anatolii V. Mokshin

In liquid pnictogens, quasi-stable structures can be formed near melting temperature. The nature of their stability does not have the unified point of view. In the present work, the task of determining the degree of atomic bonding in these structures is solved using the Crystal Orbital Hamilton Population (COHP) method. The original results of ab-initio simulation of arsenic, antimony and bismuth melts near their melting temperatures are used. It is shown that the features of the electron interaction at the level of $p$-orbitals determine the characteristic bond lengths and angles between atoms. It has been established that the stability of structures decreases according to a power law with an increase in the atomic mass of a chemical element and the number of atoms in the structure. The obtained results clarify the understanding the mechanisms of formation of quasi-stable structures in pnictogen melts from first principles.
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Materials Science · Cross-listed from cond-mat.str-el

Manipulating the metal-insulator transitions in correlated vanadium dioxide through bandwidth and band-filling control

Xiaohui Yao, Jiahui Ji and Xuanchi Zhou

The metal-insulator transition (MIT) in correlated oxide systems opens up a new paradigm to trigger the abruption in multiple physical functionalities, enabling the possibility in unlocking exotic quantum states beyond conventional phase diagram. Nevertheless, the critical challenge for practical device implementation lies in achieving the precise control over the MIT behavior of correlated system across a broad temperature range, ensuring the operational adaptability in diverse environments. Herein, correlated vanadium dioxide (VO2) serves as a model system to demonstrate effective modulations on the MIT functionality through bandwidth and band-filling control. Leveraging the lattice mismatching between RuO2 buffer layer and TiO2 substrate, the in-plane tensile strain states in VO2 films can be continuously adjusted by simply altering the thickness of buffer layer, leading to a tunable MIT property over a wide range exceeding 20 K. Beyond that, proton evolution is unveiled to drive the structural transformation of VO2, with a pronounced strain dependence, which is accompanied by hydrogenation-triggered collective carrier delocalization through hydrogen-related band filling in t2g band. The present work establishes an enticing platform for tailoring the MIT properties in correlated electron systems, paving the way for the rational design in exotic electronic phases and physical phenomena.
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Materials Science · Cross-listed from physics.app-ph

Material combination optimization for brazed ceramic-metal composites using Artificial Intelligence

Sunita Khod, Vinay Kamma, Ravi Kumar Verma et al. (+1 more)

This study proposes an Artificial Intelligence (AI) driven methodology for predicting a combination of brazed ceramic-metal composite materials. Multiple machine learning (ML) algorithms are compared with the deep learning (DL) model. The developed models are tested using k-fold validation. Nine different input-output feature configurations are evaluated to assess the model performance. The input-output feature comprises material properties, namely, the coefficient of thermal expansion (CTE) and molecular mass of brazed ceramic-metal composite materials obtained from literature and the strength parameter (average Von Mises Stress (VMS)) estimated from Finite Element Method (FEM) simulation for joint assembly structure. A multi-output model, Autoencoder (AE), has also been developed and tested to predict various features. The ML model, namely the polynomial regression (PR), outperforms the other ML/DL models with a Mean square Error (MSE) of 0.01 for the test data. The autoencoder model with a 32-16-32 structure outperforms LR, PR, RF, and ANN with an MSE of 0.04% for the prediction of unseen data. The developed multi-output model accurately predicts all the features (single and multiple), while PR fails to accurately predict multi-output features of low importance. The developed AE model predicts the different material properties with an average error of ~0.16-3.78% with literature-reported values.
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All authors Sunita Khod, Vinay Kamma, Ravi Kumar Verma, Mayank Goswami

Materials Science · Cross-listed from physics.ins-det

The effect of magnetic fields on vertex reconstructed muon-spin spectroscopy

Pascal Isenring and Zaher Salman

The use of a Si pixel-based particle tracking scheme in muSR will, among others, allow measurements using a ten-fold increased stopped muons rate and samples ten times smaller than currently possible. Here we present simulation results to assess the effects of magnetic fields on two spectrometer configurations using a two-layered tracking scheme for the incoming and outgoing particles. At a low magnetic field of up to ~50 mT, the tracking and reconstruction accuracy is only minimally influenced. Beyond a magnetic field of ~80 mT the tracking capabilities diminish significantly. Operating a two-layered scheme using small magnetic fields hence does not require adaptations. Only at large magnetic fields, a tracking scheme that makes use of an accurate field map or the use of at least three layers must be employed to achieve reliable particle tracking.
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Materials Science

Multiscale Magnetic Correlations in La2Mn2-xNixO6: Role of Crystal Structure in Double Perovskites

A. K. Bera, K. S. Chikara, B. Saha et al. (+3 more)

The magnetic correlations in double perovskites La2Mn2-xNixO6 (x = 0.5, 0.75, 1.0, 1.25 and 1.5) have been systematically investigated across macroscopic, mesoscopic, and microscopic length scales using temperature-dependent bulk DC magnetization, neutron depolarization, and neutron powder diffraction measurements, respectivitly. The magnetic properties evolve from a long-range ferromagnetic (FM) order to a cluster ferromagnetic or spin-glass (FM or SG) behavior as the Ni concentration increases. This evolution is directly linked to changes in the crystal structure, transitioning from pure orthorhombic (x=0.5) to mixed orthorhombic and monoclinic (x=0.75-1.0), and eventually to mixed trigonal and monoclinic symmetries (x=1.25-1.5). Ni substitution enhances the magnetic ordering temperature from 170 K (x=0.5) to 280 K (x=1.0), but this is accompanied by a reduction in both magnetization and ordered magnetic moment. Beyond x=1.0, any long-range magnetic ordering is absent. Additionally, all compositions exhibit a reentrant spin-glass-like phase at low temperatures (below about 50 K). Neutron diffraction analysis confirms that long-range FM order occurs only in the orthorhombic phase, while the monoclinic and trigonal phases lack such magnetic ordering. The temperature-dependent magnetic correlations are closely connected to variations in crystal structural parameters, including lattice constants and unit cell volume. The electrical conductivity behavior, following the variable range hopping (VRH) model, highlights the role of multivalence Mn and Ni ions on the electrical properties. This study elucidates the microscopic mechanisms behind the tunable magnetic and electrical properties of La2Mn2-xNixO6, offering valuable insights for the design of advanced materials for spintronic applications.
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All authors A. K. Bera, K. S. Chikara, B. Saha, S. M. Yusuf, Mohd. Nasir, S. Sen

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

Random State Approach to Quantum Computation of Electronic-Structure Properties

Yiran Bai, Feng Xiong and Xueheng Kuang

Classical computation of electronic properties in large-scale materials remains challenging. Quantum computation has the potential to offer advantages in memory footprint and computational scaling. However, general and practical quantum algorithms for simulating large-scale materials are still lacking. We propose and implement random-state quantum algorithms to calculate electronic-structure properties of real materials. Using a random state circuit with only a few qubits, we employ real-time evolution with first-order Trotter decomposition and Hadamard test to obtain electronic density of states, and we develop a modified quantum phase estimation algorithm to calculate real-space local density of states via direct quantum measurements. Furthermore, we validate these algorithms by numerically computing the density of states and spatial distributions of electronic states in graphene, twisted bilayer graphene quasicrystals, and fractal lattices, covering system sizes from hundreds to thousands of atoms. Our results manifest that the random-state quantum algorithms provide a general and qubit-efficient route to simulating electronic properties of large-scale periodic and aperiodic materials on quantum computers.
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Materials Science

Ambient-Stable Transfer-Free Graphdiyne Wafers with Superhigh Hole Mobility at Room Temperature

Beining Ma, Jianyuan Qi and Xinghai Shen

Graphdiyne (GDY) is recognized as a compelling candidate for the fabrication of next-generation high-speed low-energy electronic devices due to its inherent p-type semiconductor characteristics. However, the development of GDY for applications in field-effect transistors (FETs), complementary metal-oxide-semiconductor (CMOS), and logic devices remains constrained by the relatively low carrier mobility reported in current experimental studies. Herein, the synthesis of layer-controlled hydrogen-substituted graphdiyne (HsGDY) films directly on silicon substrates under a supercritical CO2 atmosphere is reported, along with the fabrication of these films into HsGDY-based FETs. The transfer-free growth strategy eliminates performance degradation caused by post-synthesis transfer processes. The resulting HsGDY FETs exhibit a remarkable hole mobility of up to 3800 cm2 V-1 s-1 at room-temperature, which is an order of magnitude higher than that of most p-type semiconductors. The synthesis of transfer-free HsGDY wafers provides a new strategy for resolving the carrier mobility mismatch between p-channel and n-channel two-dimensional metal-oxide-semiconductor devices.
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Materials Science

Relationship among Structural, Disordered, Magnetism and Band Topology in MnSb2Te4(Sb2Te3)n Family

Ming Xi, Yuchong Zhang, Wenju Zhou et al. (+5 more)

Interplay between topology and magnetism induces various exotic quantum phenomena, with magnetic topological insulators (MTIs) serving as a prominent example due to their ability to host the quantum anomalous Hall effect (QAHE). However, the realization of QAHE at higher temperature approaching magnetic-transition-temperature remains a significant challenge, primarily due to the scarcity of suitable material platforms and limited understanding of the intricate relationships between band topology, magnetism, and defects. Here, we report a comprehensive investigation of MnSb2Te4(Sb2Te3)n (n = 0 - 5) single crystals, including the discovery of novel MnSb8Te13 pure phase. Experimental measurements confirm that MnSb8Te13 exhibits ferromagnetism and features topologically nontrivial electronic structures, characterized by a Dirac point located further from the conduction band and a possible larger bulk gap compared to MnBi2Te4(Bi2Te3)n (n = 0 - 3). Moreover, we systematically analyze the relationship between structure, magnetism, topology, and disorder within Mn(Sb, Bi)2Te4((Sb, Bi)2Te3)n family. Present work will shed light on the exploration of potential platforms capable of achieving QAHE near magnetic transition temperature, offering new directions for advancing topological quantum materials.
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All authors Ming Xi, Yuchong Zhang, Wenju Zhou, Famin Chen, Donghan Jia, Huiyang Gou, Tian Qian, Hechang Lei

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

Real-time dynamics with bead-Fourier path integrals. II. Bead-Fourier RPMD

Nathan London and Mohammad R. Momeni

Feynman path integrals (PIs) have found many uses in approximate quantum dynamics methods that are able to efficiently calculate real-time quantum correlation functions. The PIs typically take the form of discrete imaginary time slices over a closed path, where the slices form the “beads” of a ring polymer (RP) necklace. Some methods, such as centroid molecular dynamics (CMD), use the RP to generate an effective potential for the dynamics, while others, like RP molecular dynamics (RPMD), directly utilize the RP in real-time dynamics in order to incorporate quantum effects. The standard, discretized bead forms of CMD and RPMD can require a large number of RP beads to provide accurate results for systems where quantum effects are strong, such as at low temperatures. In Paper I, we introduced the bead-Fourier (BF) CMD method, where we utilized the inclusion of a Fourier sine series to reduce the number of beads needed to converge the CMD effective potential up to eightfold. In this work, we extend RPMD to incorporate BF-PIs in the form of BF-RPMD. We study a number of different implementations of the method through the calculation of correlation functions for both linear and non-linear operators. The effectiveness of the BF-RPMD method is sensitive to both the system and form of the operators being studied, but we show that this method is able to produce results on par with standard RPMD, with at worst twofold and up to eightfold reduction in the number of beads by including two to three Fourier components.
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Materials Science

Nitrogen-Triggered Amorphization Enables High-Performance Solid-State Electrolytes

Bolong Hong, Lei Gao, Bingkai Zhang et al. (+10 more)

Amorphous solid-state electrolytes (SSEs) hold great promise for advancing the application of all-solid-state batteries (ASSBs), owing to their favorable ionic conductivity, structural tunability, and promising electrochemical performance. However, the absence of universal design principles for amorphous SSEs limits their development. By fundamentally re-evaluating the amorphization-forming ability of amorphous SSE systems, this study establishes a nitrogen-driven universal strategy to convert diverse metal chlorides into amorphous xLi3N-MCly (0.3 < 3x < 1.9; M denotes a metal element; 2 < y < 5) SSE. Nitrogen synergistically disrupts crystalline order via distorted coordination polyhedra and N-bridged networks, while dynamic bond reorganization enables rapid Li+ migration, achieving ionic conductivity of 2.02 mS cm-1 for 0.533Li3N-HfCl4 at 25 {\deg}C. Structural-property relationships reveal that high charge density and bridging capability of N3- enhance network disorder, shorten metal coordinating atom distances, and optimize Li+ diffusion pathway connectivity. ASSBs employing 0.533Li3N-HfCl4 retain 81.87% capacity after 2000 cycles at 1000 mA g-1 with high cathode loading (6.24 mg cm-2), demonstrating engineering viability. This work provides a paradigm for rational design of high-performance amorphous SSEs.
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All authors Bolong Hong, Lei Gao, Bingkai Zhang, Pengfei Nan, Ruishan Zhang, Yuhang Li, Zhihao Lei, Ming Liu, Jing Wu, Longbang Di, Haijin Ni, Songbai Han, Jinlong Zhu

Friday 10 October

Materials Science

Predicting Crystal Structures and Ionic Conductivities in Li$_{3}$YCl$_{6-x}$Br$_{x}$ Halide Solid Electrolytes Using a Fine-Tuned Machine Learning Interatomic Potential

Jonas Böhm and Aurélie Champagne

Understanding ionic transport in halide solid electrolytes is essential for advancing next-generation solid-state batteries. This work demonstrates the effectiveness of fine-tuning the Crystal Hamiltonian Graph Network (CHGNet) universal machine learning interatomic potential to accurately predict total energies, relaxed geometries, and lithium-ion dynamics in the ternary halide family Li$_{3}$YCl$_{6-x}$Br$_{x}$ (LYCB). Starting from experimentally refined disordered structures of Li$_{3}$YCl$_{6}$ and Li$_{3}$YBr$_{6}$, we present a strategy for generating ordered structural models through systematic enumeration and energy ranking, providing realistic structural models. These serve as initial configurations for an iterative fine-tuning workflow that integrates molecular dynamics simulations and static density functional theory calculations to achieve near-ab initio accuracy at four orders of magnitude lower computational cost. We further reveal the influence of composition (varied x) on the predicted phase stability and ionic conductivity in LYCB, demonstrating the robustness of our approach for modeling transport properties in complex solid electrolytes.
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Materials Science

Raman Digital Twin of Monolayer Janus Transition Metal Dichalcogenides

Johnathan Kowalski and Liangbo Liang

Monolayer transition metal dichalcogenides (TMDs) are a key class of two-dimensional (2D) materials with broad technological potential. Their Janus counterparts exhibit unique properties due to broken out-of-plane symmetry and further enrich the functionalities of TMDs. However, experimental synthesis and identification of Janus TMDs remain challenging. It is thus highly desirable to have a rapid, simple, and in situ characterization technique to monitor, in real time, the conversion process from the parent to Janus structure. Raman spectroscopy stands out for such a task as it is a powerful, non-destructive, and very commonly used tool to characterize 2D materials both in situ and ex situ. To realize the full potential of Raman spectroscopy on rapid characterization of Janus TMDs, we present a computational "Raman digital twin" library for various monolayer Janus TMDs in both 2H and Td phases. We focus on group-6 TMDs: MoS$_2$, WS$_2$, MoSe$_2$, WSe$_2$, MoTe$_2$, WTe$_2$ and their Janus variants: MoSSe, MoSTe, MoSeTe, WSSe, WSTe, and WSeTe. Using first-principles density functional theory (DFT), we calculate their vibrational properties and predict distinct Raman fingerprints. These phonon and Raman signatures reflect each material's structural symmetry and atomic composition, enabling clear identification via Raman spectroscopy. Our theoretical work supports experimental efforts by providing benchmarks for material identification, structural analysis, and quality control. The computational library expedites the discovery and development of Janus 2D materials, facilitating tighter integration between theoretical predictions and experimental validation.
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Materials Science

Spin Hall effect in the high-resistivity high-entropy alloy AlCrMoW

Jyoti Yadav, Felix Janus, Tiago de Oliveira Schneider et al. (+3 more)

We study thin films of the high-entropy alloy system Al$_{x}$(CrMoW)$_{1-x}$, grown on Ta seed layers by magnetron co-sputtering. Between $x=0.2$ and $x=0.6$, a resistivity larger than 100$\mu\Omega$cm is achieved, with a peak of 180$\mu\Omega$cm at $x=0.5$. Around the stoichiometric composition AlCrMoW, the alloy forms a bcc solid solution. The harmonic Hall method was used to characterize the spin Hall angle of the alloy series, where a maximum spin Hall angle of $\theta = -0.12 \pm 0.01$ is observed for $x=0.25$. The implied spin Hall conductivity is $\sigma_\mathrm{SH} \approx -72\,000 \, \hbar/(2e)$\,S/m. The experimental results show excellent agreement with density functional theory calculations, which show similar trends and values. The results demonstrate that high-entropy alloys with a main-group element component can form a simple crystal structure and show high resistivity. This suggests that a whole new class of materials for spin Hall device engineering is available with simple methods.
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All authors Jyoti Yadav, Felix Janus, Tiago de Oliveira Schneider, Shalini Sharma, Daniel Schröter, Markus Meinert

Materials Science

Rotation of crystal seed during early stages of growth reveals the anisotropy of glass matrix

R. Thapa, E. Mustermann, H. Jain et al. (+2 more)

Rotation of crystal seed during the early stages of growth in a glass matrix has been observed due to some torque, contradicting the expectations from the isotropic, uniform structure of the surrounding amorphous matrix. We establish an atomistic origin of this new phenomenon from molecular dynamics simulations using LiNbO3 and LiNbO3-SiO2 glasses as model systems. Effectively, it arises due to non-uniform forces on the seed from the surrounding glass, which appears inhomogeneous and anisotropic on the scale of glass-crystal interface. The seeded crystal growth (SCG) at higher temperatures amplifies this effect due to enhanced atomic dynamics. Silica, when added to LiNbO3 glass, reduces the crystal growth rate due to increased viscosity and restricted atomic mobility across the growth interface, but has minimal effect on the crystal rotation. These findings challenge a general assumption that glass is an isotropic material, especially during the early stage of its crystallization, and provide insights for tailoring the microstructure of widely used glass-ceramics.
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All authors R. Thapa, E. Mustermann, H. Jain, V. Dierolf, M. E. McKenzie

Materials Science

Dipole Alignment and Layered Flow Structure in Pressure-Driven Water Transport through MoS$_{2}$ Membranes

João Victor Lemos Vale, Lucas Cesena, Bruno H. S. Mendonça et al. (+1 more)

Efficient water transport through nanostructure membranes is essential for advancing filtration and desalination technologies. In this study, we investigate the flow of water through molybdenum disulfide (MoS$_{2}$) nanopores of varying diameters using molecular dynamics simulations. The results demonstrate that both pore size and atomic edge composition play crucial roles in regulating water flux, molecular organization, and dipole orientation. Larger pores facilitate the formation of layered water structures and promote edge-accelerated flow, driven by strong electrostatic interactions between water molecules and exposed molybdenum atoms. In narrower pores, confinement and asymmetric edge chemistry induce the ordered alignment of dipoles, thereby enhancing directional transport. Velocity and density maps reveal that pore edges act as active zones, concentrating flow and reducing resistance. These findings highlight the significance of pore geometry, surface chemistry, and molecular dynamics in influencing water behavior within MoS$_{2}$ membranes, providing valuable insights for the design of advanced nanofluidic and water purification systems.
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All authors João Victor Lemos Vale, Lucas Cesena, Bruno H. S. Mendonça, Elizane E. de Moraes

Materials Science

Ab initio study on photocatalytic properties of PtSSe-WXY Janus heterostructures

Shivprasad S. Shastri, Antonio Cammarata and Tomas Polcar

Semiconductor photocatalysis offers a sustainable route for converting solar energy into chemical energy, enabling the production of clean fuels and valuable chemical products. To this aim, we explore van der Waals heterostructures made up of Janus PtSSe and WXY (X, Y $=$ S, Se, Te and X $\neq$Y), in the context of photocatalytic applications. The redox capabilities of various heterostructure configurations (atom facing types and stacking orders) are evaluated by aligning the absolute band edge positions with respect to redox potentials of hydrogen and oxygen evolution reaction (HER and OER) and CO$_2$ reduction reactions. The stability of photocatalyst candidates are checked by layer binding energy calculations and ab initio molecular dynamics simulations. The optical absorption spectra suggest good light absorption in the visible range. Further, strain engineering is applied as a way to tune band edges and evaluate the possible use of the heterostructures as photocatalysts. This study shows that van der Waals heterostructure bilayers composed of Janus PtSSe and WSeTe in specific geometric configurations can be potential materials as photocatalysts for HER, OER and CO$_2$ reduction reactions. Finally, we suggest that, although systems made up of PtSSe and WSTe cannot be used for photocatalytic applications, they can be explored for applications in thermoelectric energy conversion or infrared photovoltaics.
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Materials Science

Orientational Order of Phenyl Rotors on Triangular Platforms on Ag and Au(111)

Behzad Mortezapour, Sebastian Hamer, Rainer Herges et al. (+2 more)

We investigated trioxatriangulenium functionalized with phenyl (phenyl-TOTA) on the (111) surfaces of Ag and Au using low-temperature scanning tunneling microscopy (STM) and density functional theory (DFT). On Ag(111), the molecules form hexagonal arrays, and on Au(111), honeycomb patterns are also observed. The orientations of the phenyl moieties are resolved on both substrates. On Ag(111), the orientations are parallel within a row and they differ by approximately $60^\circ$ between adjacent molecular rows, and STM images suggest dimerization of the molecules. DFT calculations for Ag(111) reveal that van der Waals interactions dominate this system. The optimized structure matches the experimental pattern, and the simulated STM images exhibit apparent dimerization. This dimerization results from an asymmetry of the phenyl wavefunction, which reflects intramolecular hydrogen bonding between the ligand and an oxygen atom within the triangulenium platform. The orientation of the phenyl moieties is explained by the interaction of each phenyl moiety with its triangulenium platform combined with the direct long-range interaction between phenyl moieties across molecules.
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All authors Behzad Mortezapour, Sebastian Hamer, Rainer Herges, Roberto Robles, Richard Berndt

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

Mapping the moiré potential in multi-layer rhombohedral graphene

Eric Seewald, Sanat Ghosh, Nishchhal Verma et al. (+11 more)

Rhombohedral graphene (rG) aligned with hexagonal boron nitride (hBN) has been shown to host flat bands that stabilize various strongly correlated quantum phases, including Mott insulators, integer, and fractional quantum anomalous Hall phases. In this work, we use scanning tunneling microscopy/spectroscopy (STM/STS) to visualize the dispersion of flat bands with doping and applied displacement fields in a hBN-aligned rhombohedral trilayer graphene (rtG)/hBN moiré superlattice. In addition to the intrinsic flat bands of rtG induced by the displacement field, we observe low-energy features originating from moiré potential-induced band folding. Real-space variations of the spectroscopic features allow us to quantify the spatial structure of the moiré potential at the rtG/hBN interface. Importantly, we find that accurately capturing the moiré site-dependent spectra requires incorporating a moiré potential acting on the top graphene layer with a sign opposite to that of the bottom layer into the continuum model. Our results thus provide key experimental and theoretical insights into understanding the role of the moire superlattice in rG/hBN heterostructures.
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All authors Eric Seewald, Sanat Ghosh, Nishchhal Verma, John Cenker, Yinan Dong, Birui Yang, Amit Basu, Takashi Taniguchi, Kenji Watanabe, Mandar M. Deshmukh, Dmitri N. Basov, Raquel Queiroz, Cory Dean, Abhay N. Pasupathy

Materials Science

Insights into the OER, ORR, and HER Activity of a New MXene-Family SnSiGeN4 Photocatalyst for Water Splitting: A First-Principles Study

Chhatra Bahadur Subba, Bhanu Chettri, Amel Laref et al. (+4 more)

The development of efficient and cost-effective catalysts for clean energy conversion remains a central challenge in materials science. Although platinum serves as the benchmark catalyst, its scarcity and high cost hinder large-scale deployment. In this study, we propose a newly predicted SnSiGeN4 MXene-family monolayer as a promising candidate for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER). Using first-principles calculations, we systematically investigated its electronic, vibrational, and optical properties across multiple exchange-correlation functionals, including hybrid approaches, revealing a wide and tunable band gap. Simulated infrared and Raman spectra further confirm the dynamical stability and the presence of catalytically active sites. Guided by these findings, we studied photocatalytic reaction analyses that demonstrate that the computed overpotentials for OER, ORR, and HER are comparable to those of Pt-based catalysts and outperform Ir-based systems, positioning SnSiGeN4 as a sustainable, high-performance platform for next-generation UV-visible-light-driven photocatalysis.
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All authors Chhatra Bahadur Subba, Bhanu Chettri, Amel Laref, Zeesham Abbas, Amna Parveen, Dibya Prakash Rai, Zaithanzauva Pachuau

Materials Science

Optically induced orbital polarization in bulk germanium

Francesco Scali, Marco Finazzi, Federico Bottegoni et al. (+1 more)

Optical orientation has been proven as a powerful tool to inject spin-polarized electron and hole populations in III-V and group-IV semiconductors. In particular, the absorption of circularly-polarized light in bulk Ge generates a spin-oriented population of electrons in the conduction band with a spin-polarization up to 50%, whereas the hole spin-polarization, opposite to the electron one, can even reach values up to 83%. In this letter, we theoretically investigate the optical injection of orbital polarization by means of circularly-polarized light in bulk Ge and we show that the latter considerably exceeds 100% for holes and photon energies close to the direct Ge gap. These results suggest that Ge is a convenient platform for future development of orbitronics and opto-orbitronic devices.
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All authors Francesco Scali, Marco Finazzi, Federico Bottegoni, Carlo Zucchetti

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

Is Platinum a Proton Blocking Catalyst?

Aparna Saksena, Yujun Zhao, J. Manoj Prabhakar et al. (+3 more)

Platinum, to date, is the most widely applied electrocatalyst for hydrogen evolution reaction (HER) in acidic media. It is assumed to be a proton-blocking catalyst with only surface-limited adsorption of the reaction intermediates. Here, we critically evaluate the bulk interaction of Pt with hydrogen (H), and its heavier isotope deuterium (D), by monitoring operando mass change of the Pt electrode during galvanostatic heavy/water splitting by employing an electrochemical quartz crystal microbalance. Unexpectedly, we observe an irreversible temporal mass gain and a change in the reaction's overpotential, arising from diffusion of H/D into Pt, confirmed by atom probe tomography and thermal desorption spectroscopy. Sub-surface concentration of at least ca. 15 at. % of D in Pt was observed, diffusing down to a depth of more than 10 nm. Analytical description quantified the diffusion coefficient of D in Pt to be 3.2X10^-18 cm2Xs-1. These findings challenge the existing credence of Pt-proton interaction being limited to the surface, prompting the expansion of the catalyst design strategies to account for property-modifying bulk diffusion of H/D in the Pt matrix
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All authors Aparna Saksena, Yujun Zhao, J. Manoj Prabhakar, Dierk Raabe, Baptiste Gault, Yug Joshi

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

Advances in momentum-resolved EELS of phonons, excitons and plasmons in 2D materials and their heterostructures

Cana Elgvin, Fredrik S. Hage, Khairi F. Elyas et al. (+4 more)

Functional nanomaterials, including 2D materials and their heterostructures are expected to impact fields ranging from catalysis, optoelectronics to nanophotonics. To realize their potential, novel experimental approaches need to be developed to characterize the combined materials and their components. Techniques using fast electrons, such as electron energy-loss spectroscopy (EELS), probe phenomena over an unrivaled energy range with high resolution. In addition, momentum-resolved EELS simultaneously records energy and momentum transfer to the sample and thus generates two-dimensional data sets for each beam position. This allows excitations that occur at large momentum transfer to be resolved, including those outside of the light cone and beyond the first Brillouin zone, all whilst retaining nanometer sized spatial selectivity. Such capabilities are particularly important when probing phonons, plasmons, excitons and their coupling in 2D materials and their heterostructures.
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All authors Cana Elgvin, Fredrik S. Hage, Khairi F. Elyas, Katja Höflich, Øystein Prytz, Christoph T. Koch, Hannah C. Nerl

Materials Science

Room temperature optical control of spin states in organic diradicals

Rituparno Chowdhury, Alistair Inglis, Lucy E. Walker et al. (+13 more)

We report a family of luminescent alternant diradicals which, at room temperature, support a ground-state spin-triplet, near-unity photoluminescence quantum yields, and optical spin addressability. These diradicals comprise trityl groups meta-linked via pyridyl or phenyl groups, enabling optically bright triplet-to-triplet and singlet-to-singlet transitions. At room temperature, we observe optically detected magnetic resonance in these systems at zero magnetic field and a strong magneto-photoluminescence (10% modulation at 2 mT applied magnetic field). Distinct photoluminescence bands (at 630 nm and 700 nm) show opposite-sign spin-optical responses, arising from spin-selective intersystem crossing between triplet and singlet manifolds. These bright, all-organic diradicals offer a new set of chemically tunable materials for room temperature spin-optical interfaces, paving the way for application as quantum sensors.
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All authors Rituparno Chowdhury, Alistair Inglis, Lucy E. Walker, Petri Murto, Chiara Delpiano-Cordeiro, Colin Morrison, Naitik A. Panjwani, Yao Fu, Yan Sun, Wei Zhou, Peter J. Skabara, Akshay Rao, Alexei Chepelianskii, Hugo Bronstein, Sam L. Bayliss, Richard H. Friend

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

Understanding How Synthetic Impurities Affect Glyphosate Solubility and Crystal Growth Using Free Energy Calculations and Molecular Dynamics Simulations

Alejandro Castro, Ignacio Sanchez-Burgos, Nuria H. Espejo et al. (+3 more)

Glyphosate, the most widely used herbicide worldwide, crystallizes through complex intermolecular interactions that are strongly influenced by synthesis-derived impurities. Understanding this process at the molecular scale is critical for optimizing production, ensuring product quality, and assessing environmental impact. Here, we employ direct coexistence molecular dynamics simulations and free energy calculations to elucidate how glycine-a prevalent synthesis byproduct-modulates glyphosate solubility and crystal growth in aqueous solutions. Our simulations identify two major mechanisms by which glycine hinders crystallization. First, direct coexistence simulations show that glycine preferentially adsorbs at crystal surfaces, hindering glyphosate attachment and slowing growth. Second, free energy calculations demonstrate that glycine enhances glyphosate solubility, reducing the supersaturation driving force to incorporate into the crystal phase. Experimental measurements corroborate our predictions, confirming both enhanced solubility and reduced crystallization kinetics in glycine-bearing systems. These findings establish that glycine-typically considered an inert impurity-actively disrupts glyphosate crystallization by promoting its dissolution. More broadly, this integrated computational-experimental approach highlights the power of molecular simulations to disentangle impurity effects, interfacial phenomena, and solution thermodynamics in crystallization, providing molecular-level insights for optimizing industrial protocols and predicting agrochemical behavior under relevant environmental conditions.
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All authors Alejandro Castro, Ignacio Sanchez-Burgos, Nuria H. Espejo, Adiran Garaizar, Giovanni Maria Maggioni, Jorge R. Espinosa

Materials Science

Deep prior-based denoising for state-of-the-art scientific imaging and metrology

Yuichi Yokoyama, Kohei Yamagami, Yuta Sumiya et al. (+2 more)

Deep learning has revolutionized computer vision, yet a major gap persists between complex, data-hungry deep learning models and the practical demands of state-of-the-art scientific measurements. To fundamentally bridge this gap, we propose deep prior-based denoising, a robust deep learning model that requires no training data. We demonstrate its effectiveness by removing grid artifacts in angle-resolved photoemission spectroscopy (ARPES), a long-standing and critical data analysis challenge in materials science. Our results demonstrate that deep prior-based denoising yields clearer ARPES images in a fraction of the time required by conventional, experiment-based denoising methods. This ultra-efficient approach to ARPES will enable high-speed, high-resolution three-dimensional band structure mapping in momentum space, thereby dramatically accelerating our understanding of microscopic electronic structures of materials. Beyond ARPES, deep prior-based denoising represents a versatile tool that could become a new standard in any advanced scientific measurement fields where data acquisition is limited.
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All authors Yuichi Yokoyama, Kohei Yamagami, Yuta Sumiya, Hayaru Shouno, Masaichiro Mizumaki

Materials Science

Are diffusion models ready for materials discovery in unexplored chemical space?

Sanghyun Kim, Gihyeon Jeon, Seungwoo Hwang et al. (+4 more)

While diffusion models are attracting increasing attention for the design of novel materials, their ability to generate low-energy structures in unexplored chemical spaces has not been systematically assessed. Here, we evaluate the performance of two diffusion models, MatterGen and DiffCSP, against three databases: a ternary oxide set (constructed by a genetic algorithm), a ternary nitride set (constructed by template informatics), and the GNoME database (constructed by a combination of both). We find that diffusion models generally perform stably in well-sampled chemical spaces (oxides and nitrides), but are less effective in uncommon ones (GNoME), which contains many compositions involving rare-earth elements and unconventional stoichiometry. Finally, we assess their size-extrapolation capability and observe a significant drop in performance when the number of atoms exceeds the trained range. This is attributed to the limitations imposed by periodic boundary conditions, which we refer to as the curse of periodicity. This study paves the way for future developments in materials design by highlighting both the strength and the limitations of diffusion models.
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All authors Sanghyun Kim, Gihyeon Jeon, Seungwoo Hwang, Jiho Lee, Jisu Jung, Seungwu Han, Sungwoo Kang

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

Non-Hermitian Bethe-Salpeter Equation for Open Systems: Emergence of Exceptional Points in Excitonic Spectra from First Principles

Zhenlin Zhang, Wei Hu, Enrico Perfetto et al. (+1 more)

In open quantum systems hosting excitons, dissipation mechanisms critically shape the excitonic dynamics, band-structure and topological properties. A microscopic understanding of excitons in such non-Hermitian settings demands a first-principles generalization of the Bethe-Salpeter equation (BSE). Building on a recently introduced nonequilibrium Green's function formalism compatible with Lindbladian dynamics, we derive a non-Hermitian BSE from diagrammatic perturbation theory on the Keldysh contour, and obtain a microscopic excitonic Hamiltonian that incorporates dissipation while preserving causality. We apply the formalism to valley excitons in transition metal dichalcogenides coupled to structured photon baths. We uncover a rich landscape of exceptional points in momentum space, forming either discrete sets or continuous manifolds, depending on bath structure. The exceptional points give rise to nonanalytic valley-polarization, unusual polarization pattern in photoluminescence, and nontrivial topological signatures. Our results establish a first-principles framework for predicting and controlling excitonic behavior in open quantum materials, showing how engineered environments can be leveraged to induce and manipulate non-Hermitian and topological properties.
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All authors Zhenlin Zhang, Wei Hu, Enrico Perfetto, Gianluca Stefanucci

Materials Science

Magnetically Assisted Separation of Weakly Magnetic Metal Ions in Porous Media.Part 1: Experiments

Alwell Nwachukwu, Muhammad Garba, Jamel Ali et al. (+3 more)

We report experiments on the magnetophoresis of paramagnetic (MnCl2) and diamagnetic (ZnCl2) metal ions in porous media under the influence of a non-uniform magnetic field generated by a permanent magnet. Experiments were carried out in a range of initial ion concentrations (1-100 mM), porous media particle sizes (63 um and 500 um), and varying mixture ratios of metal ion concentrations. For single-ion magnetophoresis, paramagnetic MnCl2 migrated toward the magnet surface, with an enrichment of approximately 2-4 percent near regions of high magnetic field. Conversely, diamagnetic ZnCl2 moved away from regions of highest magnetic field gradients, with depletion levels of 0.5-1.8 percent relative to the initial concentration. Our results demonstrate that magnetophoresis is directly proportional to porous media particle size, increasing with larger particle sizes, a trend attributed to the reduced drag forces experienced by the ions in media with larger particles. Interestingly, in binary mixtures, both MnCl2 and ZnCl2 migrated toward regions of highest magnetic field, contrary to their individual behaviors. The magnetophoretic effect of MnCl2 was diminished with increasing concentrations of ZnCl2, indicating interactions between the two ions. These findings suggest that both metal ions undergo field-induced cluster formation, with cluster sizes in the micrometer range, in both single and binary ion systems. In binary mixtures, the two ions appear to interact, potentially forming mixed clusters containing both MnCl2 and ZnCl2.
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All authors Alwell Nwachukwu, Muhammad Garba, Jamel Ali, Theo Siegrist, Munir Humayun, Hadi Mohammadigoushki

Materials Science

Configurational Entropy-Driven Phase Stability and Thermal Transport in Rock-Salt High-Entropy Oxides

Ashutosh Kumar, Adrien Moll, Jitendra Kumar et al. (+3 more)

High-entropy oxides (HEOs) offer a unique platform for exploring the thermodynamic interaction between configurational entropy and enthalpy in stabilizing complex solid solutions. In this study, a series of rock-salt structured oxides with varying configurational entropy, ranging from binary to multi-cation systems, to elucidate the competing roles of enthalpy and entropy in phase stabilization is investigated. Compositions including (Ni$_{0.8}$Cu$_{0.2}$)O to(NiCuZnCoMg)$_{0.9}$A$_{0.1}$O (A = Li, Na, K) were synthesized and their stuctural, microstructural and thermal properties have been discussed. X-ray diffraction combined with thermal cycling confirms that even a medium configurational entropy ($\sim$ 0.95R) can induce single-phase behavior stabilized by configurational entropy ($\Delta S_{conf}$), challenging the traditional threshold of $1.5\,R$. High-resolution TEM and EDS mapping reveal nanocrytalline features and homogeneous elemental distribution respectively, while XPS analysis confirms divalent oxidation states. A strong coupling between high configurational entropy with thermal conductivity ($\kappa$) has been observed. First, a sharp decrease in $\kappa$ with increasing $\Delta S_{conf}$ is seen and then decomposed samples (while cooling) show high $\kappa$, demonstrating the role of $\Delta S_{conf}$ on $\kappa$. Furthermore, Li-doped compositions exhibit improved thermoelectric performance, with a maximum figure of merit ($zT$) of $\sim$0.15 at 1173K\, driven by low thermal conductivity and favorable carrier transport. The results highlight that configurational entropy, even at intermediate values, plays a significant role in stabilizing disordered single-phase oxides and tailoring phonon transport.
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All authors Ashutosh Kumar, Adrien Moll, Jitendra Kumar, Diana Dragoe, David Bérardan, Nita Dragoe

Materials Science

Magnetic Materials for Quantum Magnonics

Rostyslav O. Serha, Carsten Dubs and Andrii V. Chumak

Quantum magnonics studies the quantum properties of magnons, the quanta of spin waves, and their application in quantum information processing. Progress in this field depends on identifying magnetic materials with characteristics tailored to the diverse requirements of magnonics and quantum magnonics. For single-magnon excitation, its control, hybrid coupling, and entanglement, the most critical property is the ability to support long magnon lifetimes. This perspective reviews established and emerging magnetic materials, including ferromagnetic metals, Heusler compounds, antiferromagnets, altermagnets, organic and 2D van der Waals magnets, hexaferrites, europium chalcogenides, and in particular yttrium iron garnet (YIG), highlighting their key characteristics. YIG remains the benchmark, with bulk crystals supporting sub-microsecond Kittel-mode lifetimes and ultra-pure spheres achieving $\sim18\,\mu$s for dipolar-exchange magnons at millikelvin temperatures. However, thin YIG films on gadolinium gallium garnet (GGG) substrates suffer from severe lifetime reduction due to substrate-induced losses. In contrast, YIG films on a new lattice matched, diamagnetic alternative, yttrium scandium gallium/aluminum garnet (YSGAG), overcomes these limitations and preserves low magnetic damping down to millikelvin temperatures. These advances provide a practical pathway toward ultralong-living magnons in thin films, enabling scalable quantum magnonics with coherent transport, strong magnon-photon, magnon-qubit coupling, and integrated quantum networks.
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