Peer Revenue Equity in science

Papers

Fresh from arXiv, typeset properly. Highlighted words trade on the market.

Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Tuesday 4 November

Materials Science

Bandgap Engineering On Demand in GaAsN Nanowires by Post-Growth HydrogennImplantation

Nadine Denis, Akant Sharma, Elena Blundo et al. (+9 more)

Bandgap engineering in semiconductors is required for the development of photonic and optoelectronic devices with optimized absorption and emission energies. This is usually achieved by changing the chemical or structural composition during growth or by dynamically applying strain. Here, the bandgap in GaAsN nanowires grown on Si is increased post-growth by up to 460 meV in a reversible, tunable, and non-destructive manner through H implantation. Such a bandgap tunability is unattained in epilayers and enabled by relaxed strain requirements in nanowire heterostructures, which enables N concentrations of up to 4.2% in core-shell GaAs/GaAsN/GaAs nanowires resulting in a GaAsN bandgap as low as 0.97 eV. Using micro-photoluminescence measurements on individual nanowires, it is shown that the high bandgap energy of GaAs at 1.42 eV is restored by hydrogenation through formation of N-H complexes. By carefully optimizing the hydrogenation conditions, the photoluminescence efficiency increases by an order of magnitude. Moreover, by controlled thermal annealing, the large shift of the bandgap is not only made reversible, but also continuously tuned by breaking up N-H complexes in the hydrogenated GaAsN. Finally, local bandgap tuning by laser annealing is demonstrated, opening up new possibilities for developing novel, locally and energy-controlled quantum structures in GaAsN nanowires.
Read the full abstract

All authors Nadine Denis, Akant Sharma, Elena Blundo, Francesca Santangeli, Paolo De Vincenzi, Riccardo Pallucchi, Mitsuki Yukimune, Alexander Vogel, Ilaria Zardo, Antonio Polimeni, Fumitaro Ishikawa, Marta DeLuca

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

Model for charge carrier spectra in topological semimetals of the TaAs family

G. P. Mikitik and Yu. V. Sharlai

We propose a four-band model describing the electron energy spectra near the Weyl points in the topological semimetals of the TaAs family (TaAs, TaP, NbAs, NbP). This model takes into account the fact that these Weyl points result from the band-contact lines which would exist in the mirror-reflection planes of these materials if the spin-orbit interaction were absent in them. Within this model, we obtain conditions for the existence of the Weyl points, determine their positions in the Brillouin zone, and derive the explicit formula for dispersion of the bands along the straight line connecting the two close Weyl points with opposite topological charges. Using NbP as an example, the values of the parameters defining the model spectrum are found. The obtained results show that for the semimetals of the TaAs family, the charge-carriers spectrum in the vicinity of the two close Weyl points can be analyzed without complex band-structure calculations.
Read the full abstract

Materials Science

Time-Reversed Superfluorescence in a Polaronic Quantum Material

Arnab Ghosh, Patrick Brosseau, Dmitry N. Dirin et al. (+2 more)

Superfluorescence, the cooperative burst of spontaneous emission from an ensemble of dipoles, arises when microscopic oscillators spontaneously synchronize their phases. Here we show that this process can be reversed in time within quantum materials. Coherent multidimensional spectroscopy of halide perovskite quantum dots reveals a delayed cooperative absorption burst, the mirror image of superfluorescent emission, driven by transient polaron fields that phase-lock unit-cell dipoles within 100 fs. The effect scales systematically with quantum-dot size and halide composition, reaching near-unity coherence fidelity even at 300 K. A microscopic exciton-polaron model reproduces the buildup and decay of the coherent state, identifying lattice polarons as the mediators of synchronization. These results demonstrate that many-body temporal coherence can self-organize and persist at room temperature, opening routes toward engineered collective optical states and superabsorbing quantum devices.
Read the full abstract

All authors Arnab Ghosh, Patrick Brosseau, Dmitry N. Dirin, Maksym V. Kovalenko, Patanjali Kambhampati

Materials Science

Exploring mechanisms leading to composition errors in monazite (CePO4) analysed with atom probe tomography

Tom Veret, Fabien Delaroche, Ivan Blum et al. (+6 more)

Monazite (CePO4) is widely used in U-Th-Pb geochronology due to its reliable age determinations, although isotopic disturbances often require nanoscale investigation to better understand the mechanisms at play. Atom Probe Tomography (APT) offers unique capabilities for nanoscale chemical analysis and 3D atomic reconstruction but presents challenges for insulating materials such as CePO4, particularly due to oxygen loss during field evaporation. This study investigates the effects of laser wavelength, energy, metallic coatings and detection device on mass spectrum optimization and compositional accuracy in synthetic CePO4 samples. Results show that shorter laser wavelengths (260 nm) enhance peak resolution, particularly when combined with advanced reflectron configurations, as demonstrated with the LEAP 6000 XR. Chromium coatings further improve thermal dissipation and reduce noise levels. However, compositional measurements reveal systematic underestimation of oxygen and overestimation of P and Ce, likely influenced by preferential low-field element evaporation. These findings highlight the need to carefully tune experimental parameters to mitigate quantification biases and enhance the reliability of APT analyses for geological materials.
Read the full abstract

All authors Tom Veret, Fabien Delaroche, Ivan Blum, Jonathan Houard, Benjamin Klaes, Isabelle Mouton, Frederic De-Geuser, Anne-Magali Seydoux-Guillaume, François Vurpillot

Materials Science

Suppression of auxetic behavior in black phosphorus with sulfur substitution

Hayden Groeschel, Arjyama Bordoloi and Sobhit Singh

Sulfur-doped black phosphorus (b-P) has recently emerged as a promising candidate for next-generation electronic and optoelectronic technologies owing to its enhanced environmental stability and tunable electronic properties. In this work, we systematically investigate the effects of sulfur substitution on the elastic, mechanical, and electronic properties of b-P, with a particular focus on its auxetic behavior (that is, negative Poisson's ratio), using first-principles density functional theory calculations. Our results unveil the fundamental origin of the intrinsic auxetic response in pristine b-P and elucidate how sulfur incorporation alters this behavior. We find that sulfur atoms distort the characteristic bow-tie structural motif responsible for the negative Poisson's ratio in b-P, thereby suppressing the in-plane auxeticity. Moreover, the resulting charge redistribution also effectively quenches the out-of-plane auxetic response of b-P. With increasing sulfur content, the bulk modulus and Poisson's ratio increase, whereas the Young's modulus, shear modulus, and Debye temperature decrease. Additionally, sulfur substitution suppresses the semiconducting properties of b-P, giving rise to metallicity. These findings highlight that although sulfur substitution enhances the environmental stability of b-P, it also substantially modifies its elastic and mechanical properties, particularly the auxetic behavior, which is an important consideration in the design of nanoscale electronic devices.
Read the full abstract

Materials Science

First-principles Prediction of Carrier Mobility in Semiconductor Nanowires Based on the Spatially Dependent Boltzmann Transport Equation

Zirui He, Shang-Peng Gao and Meng Chen

Carrier mobility in bulk semiconductors is typically governed by electron-phonon (e-ph) scattering. In nanostructures, spatial confinement can lead to significant surface scattering, lowering mobility and breaking the spatial homogeneity assumption of conventional models. In this work, a fully ab initio framework based on the spatially dependent Boltzmann transport equation for one-dimensional nanowires is developed. We apply it to Si and GaN assuming diffusive surface scattering, and reveal the mobility-diameter relation: $\mu_\mathrm{1D} = \mu_\mathrm{bulk} \left[1-\left(d/d_0\right)^{-\beta}\right]$. The parameter $d_0$, comparable to the carrier mean free path, defines a boundary layer exhibiting a considerable mobility gradient, and also quantifies the competition between e-ph and surface scattering together with $\beta$. We further discuss the effects of orientation, cross-sectional shape, and temperature. Moreover, experimental data are generally lower than our predictions, possibly due to structural imperfections, systematic errors from measurements, etc. Therefore, our theoretical method can provide an intrinsic benchmark toward optimized experimental realizations.
Read the full abstract

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

Structural reconstruction as the origin of the cuprate pseudogap

Sophie Beck and Aline Ramires

High-temperature superconductivity in the cuprates emerges from an enigmatic metallic state, known as the pseudogap, characterized by a reconstructed Fermi surface, reduced carrier density, and the appearance of Fermi arcs, whose origin remains unresolved. Here, we show that these defining signatures naturally arise from a structural reconstruction observed experimentally that introduces a symmetry-enforced sublattice degree of freedom. In the presence of spin-orbit coupling, the Fermi surface is reconstructed into small closed pockets, effectively reducing the carrier density. The same sublattice structure gives rise to matrix-element interference in angle-resolved photoemission spectroscopy, leading to the manifestation of Fermi arcs. Density functional theory calculations support this mechanism. These results demonstrate that lattice symmetry provides a unifying and experimentally verifiable framework for understanding the pseudogap regime in the cuprates.
Read the full abstract

Materials Science

Mean field magnetism and spin frustration in a double perovskite oxide with compositional complexity

Nandana Bhattacharya, Ravi Kiran Dokala, Sourav Chowdhury et al. (+9 more)

The rise of high-entropy oxides as a major functional materials design principle in recent years has prompted us to investigate how compositional disorder affects long-range magnetic ordering in double perovskite oxides. Since ferromagnetic insulators are emerging as an important platform for lossless spintronics, we consider the $RE_2$NiMnO$_6$ ($RE$ : rare-earth) family and investigate single-crystalline films of (La$_{0.4}$Nd$_{0.4}$Sm$_{0.4}$Gd$_{0.4}$Y$_{0.4}$)NiMnO$_{6}$ grown on SrTiO$_3$ (001) substrates in this work. Despite configurational disorder and high cationic size variance at the $RE$ site, the material exhibits robust ferromagnetic ordering with a Curie temperature ($T_\mathrm{c}$) of approximately 150 K. This $T_\mathrm{c}$ is consistent with the expectation based on consideration of the average ionic radii of the rare-earth ($RE$) sites in the bulk $RE_2$NiMnO$_6$. Below $T_\mathrm{c}$, Raman spectroscopy measurement finds a deviation from anharmonic behavior, where the phonon renormalization aligns with a mean-field approximation of spin-spin correlation. At lower temperature, magnetic $RE$ ions also contributed to the magnetic behavior and the system displays a reentrant spin-glass-like behavior. This study demonstrates that while a mean-field approach serves as a viable starting point for predicting the long-range transition temperature, microscopic details of the complex magnetic interactions are essential for understanding the low-temperature phase.
Read the full abstract

All authors Nandana Bhattacharya, Ravi Kiran Dokala, Sourav Chowdhury, Suresh Chandra Joshi, Subha Dey, Jayjit Kumar Dey, Subhajit Nandy, Daniel Perez Salinas, Manuel Valvidares, Moritz Hoesch, Roland Mathieu, Srimanta Middey

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

Adhesive strength of bio-inspired fibrillar arrays in the presence of contact defects

Agostinelli Daniele, Shojaeifard Mohammad and Bacca Mattia

The performance of bio-inspired fibrillar adhesives can be compromised by surface roughness, manufacturing imperfections or impurities. Previous studies investigated the cases of distributed defects on the array, and defects at the level of single fibrils. However, the influence of localized, macroscopic defects remains largely unexplored. Using numerical simulations of a discrete mechanical model for a fibrillar adhesive with a thick backing layer, we investigate how the size and location of a single circular defect affect the established scaling law between the adhesion force ($F$) and the effective compliance of the system ($\beta$), \ie, $F \propto \beta^{-1/2}$. We find that edge defects are generally more detrimental than central ones, as they act as pre-cracks that amplify stress concentrations at the adhesive's edge, accelerating a crack-like failure. Consequently, the established adhesion scaling law is preserved, with the defect only reducing the effective contact area. In contrast, a central defect fundamentally alters the mechanics of detachment. By transforming the contact geometry into an annulus, it promotes more uniform load sharing across the remaining fibrils and mitigates the edge-dominated failure mechanism. This change makes the adhesive strength less sensitive to the compliance of the system, as reflected by a less negative scaling exponent. The transition between these two regimes appears to occur for defects whose boundary merges with the one of the adhesive. These results provide practical guidance for the design, engineering and quality control of bio-inspired fibrillar adhesives.
Read the full abstract

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

Unlocking n-alk-1-ynes Conformers: Quantum "Trigger Finger" versus "Stiff Joint" Conformations

Ioan Bâldea

Molecular conformation in n-alk-1-ynes (CnA) is conventionally simplified to an all-planar structure. We report a comprehensive quantum chemical analysis revealing two near-isoenergetic rotamers at the acetylenic terminus: planar (C$_s$) and skewed (C$_1$). The high, symmetric rotational energy barrier ($\approx 150$\,meV) arises from unique steric relief near the $\mathrm{sp}$ center coupled with electronic stabilization of C$_1$. This creates a unique kinetic profile: a Quantum “Trigger Finger” ($\alpha$ rotation) that enforces an $\approx 50\%:\,50\%$ $\mathrm{C}_s/\mathrm{C}_1$ ensemble, sharply contrasting with the thermodynamically biased “Stiff Joint” ($\delta$ rotation) of the alkyl chain. This structural degeneracy necessitates ensemble averaging for spectroscopic data interpretation, while the slow interconversion permits kinetic trapping and intentional conformer enrichment during synthesis and molecular junction fabrication. Our work redefines the alkyne anchor, providing a blueprint for accurate interpretation of spectroscopic data and achieving conformational control in molecular electronics.
Read the full abstract

Materials Science

Ultrafast magnetic moment transfer and bandgap renormalization in monolayer FeCl$_2$

Yu-Hui Song, Huan-Cheng Yang, Kai Liu et al. (+1 more)

The microscopic origin of laser-induced ultrafast demagnetization remains an open question, to which the non-thermal electronic distribution plays a vital role at the initial stage. Herein, we investigate the connection between the non-thermal electronic distribution and the ultrafast spin dynamics as well as the electronic structure evolution in ferromagnetic FeCl$_2$ monolayer using real-time time-dependent density functional theory (rt-TDDFT) with self-consistent Hubbard $U$ correction. Our simulations reveal that femtosecond laser pulses induce ultrafast magnetic moment transfer from Fe to Cl atoms. More importantly, through a comprehensive analysis of orbital-resolved electronic structure, we elucidate the microscopic origin of this transfer, attributing it to specific intra-atomic and inter-atomic charge transfer pathways driven by non-thermal excitations. The extent of demagnetization of Fe atoms exhibits a non-monotonic dependence on the laser photon energy, reaching a maximum at the resonant excitation. In addition, the dynamical evolution of the band structure was studied based on the eigenstates of the instantaneous Hamiltonian. Under resonant excitation, the bandgap reduction reaches up to $41\%$ within tens of fs. These findings provide fundamental insights into ultrafast spin control and suggest a strategy to optically engineer the magnetism in two-dimensional magnetic materials.
Read the full abstract

All authors Yu-Hui Song, Huan-Cheng Yang, Kai Liu, Zhong-Yi Lu

Materials Science

Non-altermagnetic spin texture in MnTe

Meng Zeng, Pengfei Liu, Ming-Yuan Zhu et al. (+19 more)

Recently, altermagnets have emerged as promising candidates in spintronics, uniquely combining large spin-polarized electronic states with zero net magnetization. A prominent example is $\alpha$-MnTe, whose altermagnetic spin splitting, i.e., the degeneracy lift in momentum space induced by collinear magnetic order, has been experimentally observed. However, the direct evidence of its $g$-wave spin polarization, the key property for altermagnetic spintronics, is thus far lacking. By combining high-resolution spin- and angle-resolved photoemission spectroscopy (SARPES) with first-principles calculations, we reveal a $k_z$-independent, Rashba-like spin texture in $\alpha$-MnTe. Our results indicate that the observed spin polarization is primarily governed by spin-orbit coupling, whereas the magnetic order contributes to the splitting of energy bands but plays a much less dominant role in spin polarization due to the multi-domain nature. From this result, we further establish a way to prescreen altermagnet candidates that favor the formation of large antiferromagnetic domains based on symmetry analysis. Our work elucidates the interplay between magnetic order and spin-orbit coupling in governing spin polarization in altermagnet candidates, and thereby advances the materials design paradigm for spin-functional devices.
Read the full abstract

All authors Meng Zeng, Pengfei Liu, Ming-Yuan Zhu, Naifu Zheng, Xiang-Rui Liu, Yu-Peng Zhu, Tian-Hao Shao, Yu-Jie Hao, Xiao-Ming Ma, Gexing Qu, Rafał Kurleto, Dawid Wutke, Rong-Hao Luo, Yue Dai, Xiaoqian Zhang, Koji Miyamoto, Kenya Shimada, Taichi Okuda, Kiyohisa Tanaka, Yaobo Huang, Qihang Liu, Chang Liu

Materials Science

Parity Anomalous Semimetal with Minimal Conductivity Induced by an In-Plane Magnetic Field

Binbin Wang, Jiayuan Hu, Bo Fu et al. (+5 more)

The interplay between topological materials and local symmetry breaking gives rise to diverse topological quantum phenomena. A notable example is the parity anomalous semimetal (PAS), which hosts a single unpaired gapless Dirac cone with a half-integer quantized Hall conductivity. Here, we realize this phase in a magnetic topological sandwich structure by applying an in-plane magnetic field. This configuration aligns the magnetization of one surface in-plane while preserving magnetization out-of-plane on the opposite surface, satisfying the condition for a gapless surface state near the Fermi level on only one surface. Our key evidence is a distinctive two-stage evolution of the conductivity tensor ($\sigma_{xy}$, $\sigma_{xx}$). The first stage culminates in the PAS at the fixed point ($\frac{e^2}{2h}$, $m \frac{e^2}{h}$), where $m \approx 0.6$ corresponds to the minimal longitudinal conductivity of a single gapless Dirac cone of fermions on a 2D lattice. This PAS state remains stabilized and is superposed with a gapped band flow in the second stage. This observation demonstrates that this state stabilized by the in-plane field resists localization–contrary to conventional expectations for 2D electron systems with broken time reversal symmetry. The dynamic transition from an integer quantized insulator to a half-integer quantized semimetal establishes this material system as a versatile platform for exploring parity anomaly physics.
Read the full abstract

All authors Binbin Wang, Jiayuan Hu, Bo Fu, Jiaqi Li, Yunchuan Kong, Kai-Zhi Bai, Shun-Qing Shen, Di Xiao

Materials Science

Strain-Tunable Opto-electronics in PdS$_2$ Monolayer: the Role of Band Nesting and Carrier-Phonon Scattering

Hongfa Wang, Yancheng Gong, Subrahmanyam Pattamatta et al. (+3 more)

Strain engineering is a powerful strategy for tuning the optoelectronic properties in two-dimensional materials, yet the underlying mechanisms governing their strain response are often not fully elucidated. In this work, our first-principle calculations show that the penta-orthorhombic PdS$_2$ monolayer exhibits two key strain-tunable properties: a continuous redshift of its main optical absorption peak from $\sim$2.0 to $\sim$1.6~eV and enhancement in carrier mobility, with a more than threefold increase for electron under 0–4% biaxial tensile strain. Subsequent analysis reveals that the tunable optical response originates from a robust band nesting feature between the highest valence and lowest conduction bands, which is preserved across the Brillouin zone under biaxial strain. For the carrier transport, deformation potential theory predicts mobility increasing with strain, strongly correlating with the reduction of carrier effective mass. Our first-principles calculations show a strain-induced monotonic decrease in carrier linewidths near the band edges, indicating suppressed carrier-phonon scattering and longer carrier lifetime as the origin of the mobility enhancement. Our work establishes a pathway for engineering the optoelectronic response in 2D semiconductors where strong band nesting governs the optical properties and paves the way for the rational design of continuously tunable flexible optoelectronic devices.
Read the full abstract

All authors Hongfa Wang, Yancheng Gong, Subrahmanyam Pattamatta, Junwen Li, Hailong Wang, Zhizi Guan

Materials Science

$C_{3}$-Symmetry-induced Antisymmetric Planar Hall effect and Magnetoresistance in Single-Crystalline Ferromagnets

W. J. Qin, B. Yang, Y. Z. Tian et al. (+7 more)

The planar Hall effect (PHE) is typically symmetric under magnetic field reversal, as required by the Onsager reciprocity relations. Recent advances have identified the antisymmetric PHE (under magnetic field reversal) as an intriguing extension in magnetic systems. While new mechanisms have been proposed, the role of conventional anisotropic magnetoresistance (AMR) in this phenomenon remains unclear. Here, we report the experimental discovery of an antisymmetric (with respect to both magnetic field and magnetization) PHE and magnetoresistance in single-crystal $Co_{30}Pt_{70}$ (111) thin films with $C_{3}$ rotational symmetry and perpendicular magnetic anisotropy (PMA). We demonstrate that both antisymmetric effects arise naturally from the intrinsic fourth-rank AMR tensor inherent to C3-symmetric planes, assisted by PMA. Our findings link conventional AMR to antisymmetric galvanomagnetic responses, offering new insights into symmetry-governed transport in crystalline ferromagnets.
Read the full abstract

All authors W. J. Qin, B. Yang, Y. Z. Tian, B. W. Zheng, K. Y. Wang, B. Y. Huang, Y. B. Yang, W. Q. Zou, D. Wu, P. Wang

Materials Science

Pressure-Driven Phase Evolution and Optoelectronic Properties of Lead-free Halide Perovskite Rb$_2$TeBr$_6$

Suvashree Mukherjee, Asish Kumar Mishra, K.A. Irshad et al. (+2 more)

The structural, vibrational, and optical properties of Rb$_2$TeBr$_6$ have been investigated under high pressure using synchrotron X-ray diffraction, Raman spectroscopy, photoluminescence (PL), and optical absorption measurements. At ambient conditions, Rb$_2$TeBr$_6$ crystallizes in the cubic Fm-3m structure, which remains stable below 8.0 GPa. Within this pressure range, subtle inter-octahedral rotations develop, producing a gradual localized deviation from the ideal cubic framework. This local reorientation facilitates radiative recombination, leading to a pronounced enhancement of PL intensity with pressure up to 2.4 GPa. Beyond this pressure point, enhancement of nonradiative relaxation channels result in gradual PL quenching. Additionally, the PL intensity increases upon the application of an external weak magnetic field. A structural transition to the orthorhombic Pnnm phase occurs at around 8.0 GPa, followed by a monoclinic P$2_1/m$ phase above 10.7 GPa, and eventual amorphization beyond 25.5 GPa. Optical absorption spectra reveal continuous band-gap narrowing upon compression. These findings demonstrate the strong coupling among lattice dynamics, electronic structure, and optical response in Rb$_2$TeBr$_6$, underscoring its potential as a pressure-tunable optoelectronic material
Read the full abstract

All authors Suvashree Mukherjee, Asish Kumar Mishra, K.A. Irshad, Boby Joseph, Goutam Dev Mukherjee

Materials Science

From data to design: Random forest regression model for predicting mechanical properties of alloy steel

Samjukta Sinha and Prabhat Das

This study investigates the application of Random Forest Regression for predicting mechanical properties of alloy steel-Elongation, Tensile Strength, and Yield Strength-from material composition features including Iron (Fe), Chromium (Cr), Nickel (Ni), Manganese (Mn), Silicon (Si), Copper (Cu), Carbon (C), and deformation percentage during cold rolling. Utilizing a dataset comprising these features, we trained and evaluated the Random Forest model, achieving high predictive performance as evidenced by R2 scores and Mean Squared Errors (MSE). The results demonstrate the model's efficacy in providing accurate predictions, which is validated through various performance metrics including residual plots and learning curves. The findings underscore the potential of ensemble learning techniques in enhancing material property predictions, with implications for industrial applications in material science.
Read the full abstract

Materials Science

Hybridization Gap and Edge States in Strained-layer InAs/In0.5Ga0.5Sb Quantum Spin Hall Insulator

Wenfeng Zhang, Peizhe Jia, Wen-kai Lou et al. (+4 more)

The hybridization gap in strained-layer InAs/InxGa1-xSb quantum spin Hall insulators (QSHIs) is significantly enhanced compared to binary InAs/GaSb QSHI structures, where the typical indium composition, x, ranges between 0.2 and 0.4. This enhancement prompts a critical question: to what extent can quantum wells (QWs) be strained while still preserving the fundamental QSHI phase? In this study, we demonstrate the controlled molecular beam epitaxial (MBE) growth of highly strained-layer QWs with an indium composition of x = 0.5. These structures possess a substantial compressive strain within the In0.5Ga0.5Sb QW. Detailed crystal structure analyses confirm the exceptional quality of the resulting epitaxial films, indicating coherent lattice structures and the absence of visible dislocations. Transport measurements further reveal that the QSHI phase in InAs/In0.5Ga0.5Sb QWs is robust and protected by time-reversal symmetry. Notably, the edge states in these systems exhibit giant magnetoresistance when subjected to a modest perpendicular magnetic field. This behavior is in agreement with the Z2 topological property predicted by the Bernevig-Hughes-Zhang (BHZ) model, confirming the preservation of topologically protected edge transport in the presence of enhanced bulk strain.
Read the full abstract

All authors Wenfeng Zhang, Peizhe Jia, Wen-kai Lou, Xinghao Wang, Shaokui Su, Kai Chang, Rui-Rui Du

Materials Science · Cross-listed from cond-mat.str-el

Role of on-site Coulomb energy and negative-charge transfer in a Dirac semi-metal NiTe$_2$

A. R. Shelke, C.-W. Chuang, S. Hamamoto et al. (+7 more)

Angle-resolved photoemission spectroscopy (ARPES) combined with band structure calculations have shown that the layered transition metal dichalcogenide(TMD) NiTe$_2$ is a type-II Dirac semimetal. However, conflicting conclusions were reported regarding the role of electron correlations in NiTe$_2$. We study core-levels and valence band electronic structure of single crystal NiTe$_2$ using soft and hard x-ray photoemission spectroscopy(SXPES, HAXPES), X-ray absorption spectroscopy(XAS) and Ni $2p-3d$ Resonant-PES to quantify electronic parameters in NiTe$_2$. The Ni $3d$ on-site Coulomb energy ($U_{dd}$) is quantified from measurements of the Ni $3d$ single particle density of states(DOS) and the two-hole correlation satellite. The Ni $2p$ core level and $L$-edge XAS spectra are analyzed by charge-transfer (CT) cluster model calculations using the experimental $U_{dd}$, and it shows that NiTe$_2$ exhibits a negative CT energy $\Delta$. A comparative analysis of NiO $L$-edge XAS confirms its well-known strongly correlated CT insulator character, with a larger $U_{dd}$ and positive $\Delta$. The $d$-$p$ hybridization strength $T_{eg}$ for NiTe$_2$$<$NiO, and shows that $T_{eg}$ is not responsible for reducing $U_{dd}$ in NiTe\textsubscript{2} compared to NiO. The negative-$\Delta$ and a reduced $U_{dd}$ leads to the increase in $d^n$ count on the Ni site in NiTe$_{2}$ by nearly one electron. However, importantly, since $U_{dd}$$>$$|\Delta|$, a finite repulsive $U_{dd}$ results in pushing $d$-states away from Fermi level and this is required to make NiTe$_{2}$ a moderately correlated Dirac semi-metal with band inversion in the $p$-$p$ type lowest energy excitations.
Read the full abstract

All authors A. R. Shelke, C.-W. Chuang, S. Hamamoto, M. Oura, M. Yoshimura, N. Hiraoka, C.-N. Kuo, C.-S. Lue, A. Fujimori, A. Chainani

Materials Science · Cross-listed from physics.optics

Extending Reflectometry Range, A Zero-Crossing Algorithm for Thick Film Metrology

Zimu Zhou, Enrique Lopez-Guerra, Iulica Zana et al. (+7 more)

Accurate and high-efficiency film metrology remains a key challenge in High-Volume Manufacturing (HVM), where conventional spectroscopic reflectometry and white light interferometry (WLI) are either limited by model dependence or throughput. In this work, we extend the measurable film-thickness range of reflectometry to at least 50 um through a new model-free algorithm, the Linearized Reflectance Zero-Crossing (LRZ) method. The approach builds upon the previously reported Linearized Reflectance Extrema (LRE) technique but eliminates the sensitivity to spectral sampling and fringe attenuation that degrade performance in the thick-film regime. By linearizing phase response and extracting zero-crossing positions in wavenumber space, LRZ provides robust and repeatable thickness estimation without iterative fitting, achieving comparable accuracy with much higher computational efficiency than conventional model-based methods. Validation using more than 80 measurements on alumina films over NiFe substrates shows excellent correlation with WLI (r = 0.97) and low gauge repeatability and reproducibility (GR&R < 3%). Moreover, LRZ achieves an average Move-Acquire-Measure (MAM) time of approximately 2 s, which is about 7 times faster than WLI. The proposed method enables fast, accurate, and model-independent optical metrology for thick films, offering a practical solution for advanced HVM process control.
Read the full abstract

All authors Zimu Zhou, Enrique Lopez-Guerra, Iulica Zana, Vu Nguyen, Nguyen Quoc Huy Tran, Bojun Zhou, Gary Qian, Michael Kwan, Peter Wilkens, Chester Chien

Materials Science

Homogeneous All-Inorganic Perovskite Films via High-Pressure Recrystallization

Asma Miled, Trong Tam Nguyen, Anh Vui Nguyen et al. (+13 more)

Metal halide perovskites are promising materials for optoelectronic applications owing to their outstanding optical and electronic properties. Among them, all-inorganic perovskites such as CsPbBr$_3$ offer superior thermal and chemical stability. However, obtaining high-quality CsPbBr$_3$ thin films via solution processing remains challenging due to the precursor's low solubility, and current additive or solvent engineering strategies are often complex and poorly reproducible. High-pressure recrystallization has recently emerged as a promising route to improve film quality, yet its impact on film properties remains insufficiently explored. Here, we systematically investigate the morphological, structural, and optical properties of CsPbBr$_3$ thin films prepared by high-pressure recrystallization, in comparison with standard non-recrystallized films. Optimized recrystallization at 300 bar produces smooth, pinhole-free, single-phase 3D perovskite layers with sub-nanometer roughness, while the film thickness is precisely tunable via precursor concentration. The process enhances both grain and crystallite sizes, leading to amplified spontaneous emission with a reduced excitation threshold and improved photostability. Temperature-dependent X-ray diffraction further reveals the orthorhombic–tetragonal–cubic phase transition, consistent with single-crystal behavior. This study provides fundamental insights into pressure-driven recrystallization and establishes a reproducible, scalable approach for fabricating high-quality CsPbBr$_3$ films for optoelectronic devices.
Read the full abstract

All authors Asma Miled, Trong Tam Nguyen, Anh Vui Nguyen, José Penuelas, Aziz Benamrouche, Céline Chevalier, Thi Kim Anh Hoang, Gaëlle Trippé-Allard, Elsa Cassette, Brice Devif, Emmanuel Drouard, Emmanuelle Deleporte, Hong Hanh Mai, Abdelaziz Bouazizi, Christian Seassal, Hai Son Nguyen

Materials Science

Equivalence of charged and neutral density functional formulations for correcting the many-body self-interaction of polarons

Stefano Falletta, Jennifer Coulter, Joel B. Varley et al. (+4 more)

The electron self-interaction problem in density functional theory affects the accurate modeling of polarons, particularly their localization and formation energy. Charged and neutral density functional formulations have been developed to address this issue, yet their relationship remains unclear. Here, we demonstrate their equivalence in treating the many-body self-interaction of the polaron state. In particular, we connect with each other piecewise-linear functionals based on adding an extra charge to the supercell, the pSIC approach derived from the energetics of the neutral defect with polaronic distortions in a supercell, and the unit-cell method for polarons based on electron-phonon couplings. We show that these approaches lead to the same formal expression of the self-interaction corrected energy, which is fully defined by the energetics of the neutral charge state of the charged polaronic structure. Residual differences between these methods solely arise from the achieved polaronic structure, which is affected by different treatments of electron-screening and finite-size effects. We apply these methods to a set of prototypical small hole and electron polarons, including the hole polaron in MgO, the hole polaron in $\beta$-Ga$_2$O$_3$, the $V_\text{k}$ center in NaI, the electron polaron in BiVO$_4$, and the electron polaron in TiO$_2$. We show that the ground-state properties of polarons obtained using charged and neutral density functional formulations are in excellent agreement.
Read the full abstract

All authors Stefano Falletta, Jennifer Coulter, Joel B. Varley, Daniel Aberg, Babak Sadigh, Boris Kozinsky, Alfredo Pasquarello

Monday 3 November

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

AI-assisted design of chemically recyclable polymers for food packaging

Brandon K. Phan, Chiho Kim, Janhavi Nistane et al. (+9 more)

Polymer packaging plays a crucial role in food preservation but poses major challenges in recycling and environmental persistence. To address the need for sustainable, high-performance alternatives, we employed a polymer informatics workflow to identify single- and multi-layer drop-in replacements for polymer-based packaging materials. Machine learning (ML) models, trained on carefully curated polymer datasets, predicted eight key properties across a library of approximately 7.4 million ring-opening polymerization (ROP) polymers generated by virtual forward synthesis (VFS). Candidates were prioritized by the enthalpy of polymerization, a critical metric for chemical recyclability. This screening yielded thousands of promising candidates, demonstrating the feasibility of replacing diverse packaging architectures. We then experimentally validated poly(p-dioxanone) (poly-PDO), an existing ROP polymer whose barrier performance had not been previously reported. Validation showed that poly-PDO exhibits strong water barrier performance, mechanical and thermal properties consistent with predictions, and excellent chemical recyclability (95% monomer recovery), thereby meeting the design targets and underscoring its potential for sustainable packaging. These findings highlight the power of informatics-driven approaches to accelerate the discovery of sustainable polymers by uncovering opportunities in both existing and novel chemistries.
Read the full abstract

All authors Brandon K. Phan, Chiho Kim, Janhavi Nistane, Wei Xiong, Haoyu Chen, Woo Jin Jang, Farzad Gholami, Yongliang Su, Jerry Qi, Ryan Lively, Will Gutekunst, Rampi Ramprasad

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

Non-adiabatic perturbation theory of the exact factorisation

Matisse Wei-Yuan Tu and E.K.U. Gross

We present a novel nonadiabatic perturbation theory (NAPT) for correlated systems of electrons and nuclei beyond the Born-Oppenheimer (BO) approximation. The essence of the method is to exploit the smallness of the electronic-to-nuclear mass ratio by treating the electron-nuclear correlation terms in the electronic equation of motion of the exact factorisation (EF) framework as perturbation. We prove that any finite-order truncation of the NAPT preserves the normalisation of the conditional electronic factor as well as the gauge covariance of the resulting perturbative equations of motion. We illustrate the usefulness of NAPT by obtaining nonadiabatic corrections to the BO Berry phase in Jahn–Teller systems with a conical intersection. It well captures the departure of the exact Berry phase from being topological via the lowest-order NAPT. By removing the conical intersection with a constant gap, it further yields the correct scaling of the Berry phase toward zero.
Read the full abstract

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

Edge Irregularity Strength: A Complementary Descriptor to Topological Indices in QSPR and QSAR Studies

U. Vijaya Chandra Kumar, H.M. Nagesh and Narahari N

In chemical graph theory, topological indices are widely used as numerical descriptors for establishing quantitative structure-property relationships (QSPR) and quantitative structure-activity relationships (QSAR). These indices successfully correlate molecular structure with various physicochemical and biological properties. In addition to these methods, the concept of edge irregularity strength, a graph labeling measure, offers another perspective for representing structural characteristics. In this context, the edge irregularity strength concept provides a systematic way of assigning numerical labels to atoms based on specific rules. In this work, we explore the chemical applicability of the edge irregularity strength and demonstrate that it can also serve as a predictive tool for physicochemical properties, similar to topological indices. The findings show that the edge irregularity strength captures molecular features and complements existing approaches to structure-property analysis in chemical graph theory.
Read the full abstract

Materials Science · Cross-listed from cs.LG

COFAP: A Universal Framework for COFs Adsorption Prediction through Designed Multi-Modal Extraction and Cross-Modal Synergy

Zihan Li, Mingyang Wan, Mingyu Gao et al. (+4 more)

Covalent organic frameworks (COFs) are promising adsorbents for gas adsorption and separation, while identifying the optimal structures among their vast design space requires efficient high-throughput screening. Conventional machine-learning predictors rely heavily on specific gas-related features. However, these features are time-consuming and limit scalability, leading to inefficiency and labor-intensive processes. Herein, a universal COFs adsorption prediction framework (COFAP) is proposed, which can extract multi-modal structural and chemical features through deep learning, and fuse these complementary features via cross-modal attention mechanism. Without relying on explicit gas-specific thermodynamic descriptors, COFAP achieves state-of-the-art prediction performance on the hypoCOFs dataset under the conditions investigated in this study, outperforming existing approaches. Based on COFAP, we also found that high-performing COFs for gas separation concentrate within a narrow range of pore size and surface area. A weight-adjustable prioritization scheme is also developed to enable flexible, application-specific ranking of candidate COFs for researchers. Superior efficiency and accuracy render COFAP directly deployable in crystalline porous materials.
Read the full abstract

All authors Zihan Li, Mingyang Wan, Mingyu Gao, Xishi Tai, Zhongshan Chen, Xiangke Wang, Feifan Zhang

Materials Science · Cross-listed from cs.DB

Towards Defect Phase Diagrams: From Research Data Management to Automated Workflows

Khalil Rejiba, Sang-Hyeok Lee, Christina Gasper et al. (+3 more)

Defect phase diagrams provide a unified description of crystal defect states for materials design and are central to the scientific objectives of the Collaborative Research Centre (CRC) 1394. Their construction requires the systematic integration of heterogeneous experimental and simulation data across research groups and locations. In this setting, research data management (RDM) is a key enabler of new scientific insight by linking distributed research activities and making complex data reproducible and reusable. To address the challenge of heterogeneous data sources and formats, a comprehensive RDM infrastructure has been established that links experiment, data, and analysis in a seamless workflow. The system combines: (1) a joint electronic laboratory notebook and laboratory information management system, (2) easy-to-use large-object data storage, (3) automatic metadata extraction from heterogeneous and proprietary file formats, (4) interactive provenance graphs for data exploration and reuse, and (5) automated reporting and analysis workflows. The two key technological elements are the openBIS electronic laboratory notebook and laboratory information management system, and a newly developed companion application that extends openBIS with large-scale data handling, automated metadata capture, and federated access to distributed research data. This integrated approach reduces friction in data capture and curation, enabling traceable and reusable datasets that accelerate the construction of defect phase diagrams across institutions.
Read the full abstract

All authors Khalil Rejiba, Sang-Hyeok Lee, Christina Gasper, Martina Freund, Sandra Korte-Kerzel, Ulrich Kerzel

Materials Science

Posterior corrections for systematic distortions in atomic-resolution images from hexagonal crystals

Tyler Bortel and Peter Moeck

Digital images from crystals, as projected from the third spatial dimension and recorded in atomic resolution with any kind of real-world microscope, feature necessarily broken symmetries of the translation-periodicity-restricted Euclidean plane. The symmetry breakings are due to both the imaging process and the real structure of the imaged crystal, with the former cause typically dominating. A posterior algorithmic reduction of the symmetry breaking in such images constitutes, thus, often a correction for many of the distortions that were introduced by the imaging processes. Numerically quantified restorations of such symmetries can, therefore, be used to demonstrate the efficacy of a newly implemented posterior correction method for atomic-resolution images from hexagonal crystals. Recently developed information theory based methods are here shown to be suitable for this purpose. Thirteen experimental atomic-resolution images from graphite and monolayer molybdenite (MoS2), as respectively obtained by scanning tunneling microscopy, atomic force microscopy in the torsional resonance mode, and aberration-corrected parallel illumination transmission electron microscopy served as test cases in our larger (in its totality so far unpublished) study, from which we quote here. The source code of the software that was used for our distortion corrections and the whole report on that study are freely available on GitHub.
Read the full abstract

Materials Science · Cross-listed from cond-mat.str-el

Quantum Acoustics Demystifies the Strange Metals

Eric J. Heller, Alhun Aydin, Anton M. Graf et al. (+11 more)

Phonons have long been thought to be incapable of explaining key phenomena in strange metals, including linear-in-T Planckian resistivity from high to very low temperatures. We argue that these conclusions were based on static, perturbative approaches that overlooked essential time-dependent and nonperturbative electron-lattice physics. In fact “phonons” are not the best target for discussion, just like “photons” are not the best way to think about Maxwell's equations. Quantum optics connects photons and electromagnetism, as developed 60 years ago by Glauber and others. We have been developing the parallel world of quantum acoustics. Far from being only of academic interest, the new tools are rapidly exposing the secrets of the strange metals, revealing strong vibronic (vibration-electronic) interactions playing a crucial role forming polarons and charge density waves, linear-in-$T$ resistivity at the Planckian rate over thousands of degrees, resolution of the Drude peak infrared anomaly, and the absence of a $T^4$ low-temperature resistivity rise in 2D systems, and of a Mott-Ioffe-Regel resistivity saturation. We derive Planckian transport, polarons, CDWs, and pseudogaps from the Fröhlich model. The “new physics” has been hiding in this model all along, in the right parameter regime, if it is treated nonperturbatively. In the course of this work we have uncovered the generalization of Anderson localization to dynamic media: a universal Planckian diffusion emerges, a “ghost” of Anderson localization. Planckian diffusion is clearly defined and is more fundamental than the popular but elusive, model dependent concept of “Planckian speed limit”.
Read the full abstract

All authors Eric J. Heller, Alhun Aydin, Anton M. Graf, Joost de Nijs, Yoel Zimmermann, Xiaoyu Ouyang, Shaobing Yuan, Zixuan Chai, Siyuan Chen, Jasper Jain, Mingxuan Xiao, Chenzheng Yu, Zhongling Lu, Joonas Keski-Rahkonen

Materials Science

Directional atomic layer etching of MgO-doped lithium niobate using Br-based plasma

Ivy I. Chen, Mariya Ezzy, Emily Hsue-Chi Shi et al. (+8 more)

Lithium niobate (LiNbO$_3$, LN) is a nonlinear optical material of high interest for integrated photonics with applications ranging from optical communications to quantum information processing. The performance of on-chip devices based on thin-film lithium niobate (TFLN) is presently limited by fabrication imperfections such as sidewall surface roughness and geometry inhomogeneities over the chip. Atomic layer etching (ALE) could potentially be used to overcome these difficulties. Although an isotropic ALE process for LN has been reported, performing LN fabrication completely with ALE faces several challenges, including the lack of a directional ALE process for pattern transfer and the redeposition of involatile compounds. Here, we report a directional ALE process for LN consisting of sequential exposures of HBr/BCl$_3$/Ar plasma for surface modification and Ar plasma for removal. The HBr chemistry is found to decrease redeposition compared to F- and Cl-based plasmas, which we attribute to the higher vapor pressures of Br-based products. A grating pattern etched entirely by the process (total etch depth of 220 nm) exhibits no aspect ratio dependent etching (ARDE) down to the smallest tested gap of 150 nm, in contrast to ion milling in which ARDE manifests even at 300 nm gaps for the same etch depth. The HBr plasma chemistry is also found to support an isotropic process consisting of sequential exposures of H$_2$ plasma and HBr/BCl$_3$/Ar plasma. These processes could be used together to perform the complete fabrication process for TFLN devices, eliminating imperfections arising from ion milling.
Read the full abstract

All authors Ivy I. Chen, Mariya Ezzy, Emily Hsue-Chi Shi, Clifford F. Frez, Suraj, Lin Yi, Mahmood Bagheri, James R. Renzas, Alireza Marandi, Frank Greer, Austin J. Minnich