Materials Science
Harnessing Linear and Nonlinear Optical Responses in Ferroelectric LaMoN$_3$ for Enhanced Photovoltaic Efficiency
Surajit Adhikari, Sanika S. Padelkar, Jacek J. Jasieniak et al. (+2 more)
Nitride perovskites are an emerging class of materials predicted to exhibit diverse functional properties, yet remain underexplored due to synthesis challenges of oxygen-free nitrides. Recently, LaMoN$_3$ has been reported as an oxygen-free nitride perovskite with polar
symmetry, exhibiting excellent dynamic stability and ferroelectric properties under moderate pressure. However, its phase stability, linear and non-linear optical response, excitonic and polaronic behavior, and efficiency under high pressure remain unexplored. Applying pressure enables systematic tuning of the electronic structure properties, thereby facilitating the identification of phases optimized for either linear or nonlinear optical responses. Therefore, in this work, we systematically investigate these properties of LaMoN$_3$ up to 40 GPa using first-principles methods, including density functional theory, density functional perturbation theory, many-body perturbation theory (namely G$_0$W$_0$ and BSE), and tight binding approximation model. Our study shows that LaMoN$_3$ remains dynamically stable and retains its single-phase structure up to 40 GPa. The compound exhibits an indirect bandgap that decreases from 2.17 eV (0 GPa) to 1.45 eV (40 GPa) at the G$_0$W$_0$@PBE level. Using the BSE, we find that pressure enhances the SLME while lowering the
exciton binding energy, both favorable for photovoltaic applications. The bulk photovoltaic efficiency trend with pressure mimics the behavior of the shift current density J$_SC$ , peaking near 15 GPa before declining at higher pressures due to a diminished nonlinear shift current response. These results highlight pressure-tuned regimes to enhance photovoltaic performance. We thereby propose multi-junction device, combining absorber layers optimized for linear and nonlinear optical currents, together boosting
solar energy conversion through complementary mechanisms.
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All authors Surajit Adhikari, Sanika S. Padelkar, Jacek J. Jasieniak, Alexandr N. Simonov, Aftab Alam
Materials Science · Cross-listed from cond-mat.str-el
Emergent magnetic and charge ordered phases in freestanding ultrathin \ce{LaVO3}
Ashutosh Anand and Mukul Kabir
Transition metal
oxide perovskites are an ideal platform for exploring the interplay between
spin, orbital, charge and
lattice degrees of freedom. Among them, \ce{LaVO3} has been extensively studied in
heterostructures and superlattices, where exotic phases have been reported. Motivated by the advances in freestanding
oxide membranes, we investigate the intrinsic properties of freestanding ultrathin \ce{LaVO3} films using density functional theory. Our calculations reveal a sequence of
magnetic phase transitions with thickness, starting from stripe-AFM in monolayer until the bulk like C-AFM is recovered. Beyond four layers, polar catastrophe driven charge transfer dopes the surface layers giving rise to stripe-AFM and
ferromagnetic surface states while the central layers remain bulk like. We further explore this fact by studying charge doped monolayer, discovering that hole doping drives the system into
ferromagnetic state. Doping also induced charge ordering in the system. A striped charge ordering pattern is observed at 0.5 h/fu, while a 3:1 stripe pattern emerges at 0.25 h/fu, indicating that the periodicity of the superstructure changes with doping concentration.
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Materials Science
Donghang Xie, Haozhe Wang, Zhe Zhang et al. (+13 more)
Antiferromagnets (AFMs) hold significant potential for spintronic devices owing to their insensitivity to external
magnetic fields and the absence of stray fields. Beyond these inherent advantages, an AFM can manipulate the
magnetic dynamics of a ferromagnet (FM) layer in AFM/FM
bilayers, whereas the mechanism of such manipulation remains controversial. Here, we investigate the
magnetic dynamics of AFM/FM Mn2Au/CoFeB
bilayers via
Ferromagnetic Resonance (FMR). It is found that the Néel temperature of 2-nm-thick Mn2Au is as low as ~40 K, in sharp contrast to that of bulk Mn2Au, which exceeds 1000 K. In the Mn2Au(2 nm)/CoFeB(4 nm)
bilayer, the
magnetic damping ${\alpha}$ of the CoFeB layer increases from 0.013 to 0.047 as temperature decreases from 160 K to 10 K, accompanied by a synchronous increase in the exchange coupling field H_rot. Such an increase in ${\alpha}$ is attributed to the enhanced
spin angular momentum transfer from CoFeB to Mn2Au, mediated through AFM-FM exchange coupling between Mn2Au and CoFeB, which is enhanced by the Mn2Au
antiferromagnetic ordering as the temperature decreases. Our study provides deeper insights into AFM/FM dynamics and spintronic storage technology.
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All authors Donghang Xie, Haozhe Wang, Zhe Zhang, Zishuang Li, Jiahua Lu, Ronghua Liu, Jun Du, Bo Liu, Yu Yan, Liang He, Jing Wu, Rong Zhang, Bo Liu, Tiejun Zhou, Yongbing Xu, Xuezhong Ruan
Materials Science
Generation of an anomalous linearly dispersing spin-polarized band in Bi-based topological insulators
Matthias Kronseder, Thomas Mayer, Jan Minár et al. (+11 more)
We report the generation of an anomalous linearly dispersing,
spin-polarized band in Bi-based topological
insulator (TI) thin films, induced by soft Ar-ion bombardment followed by annealing. This extra band – which we call the anomalous linearly dispersing state (ALS) – is superimposed on the regular band structure including the topological surface state (TSS), spans an unusually large energetic range of up to ${\sim}\,\SI{650}{\milli\electronvolt}$ at the $\Gamma$-point, and appears near the
Fermi energy.
Spin-resolved measurements indicate
spin-momentum locking with a helicity opposite to that of the regular TSS. The
Fermi velocity of the ALS, $v_\mathrm{F} = (5.1\pm 0.4)\times 10^{5}\,\frac m s$, is indistinguishable from that of the regular TSS, $(5.3\pm 0.5)\times 10^{5}\,\frac m s$. The observation is reproducible across samples of varying thickness and was confirmed at two independent synchrotron radiation facilities. We discuss different mechanisms for the physical origin of the observed ALS including sputtering-induced TSS relocation, bi-layer formation by,e.g., chalcogen removal, and high-index surface relocation.
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All authors Matthias Kronseder, Thomas Mayer, Jan Minár, Magdalena Marganska, Hedwig Werner, Florian Schmid, Rebeca Diaz-Pardo, Ivana Vobornik, Jun Fuji, Cornelia Streeck, Alexander Gottwald, Hendrik Kaser, Bernd Kästner, Christian H. Back
Materials Science
Improvement of piezocatalytic performance of Na0.5Bi0.5TiO3 perovskite using K doping for efficient Rhodamine B degradation
Salma Ayadh, Salma Touili, Mbarek Amjoud et al. (+9 more)
Piezocatalysis, based on the piezoelectric properties of catalysts, breaks down the barrier between mechanical energy and chemical energy. It describes the use of charges induced by piezoelectricity to assist typical chemical processes while harvesting various forms of mechanical green energy. The performance of piezocatalysis is predominantly governed by the piezoelectric properties of materials. The main aim of this work is to evaluate and analyze the potential of potassium doped sodium bismuth titanate Na0.5-xKxBi0.5TiO3 abbreviated as NKxBT (0, 0.15, 0.20, and 0.25), as a piezocatalyst in the degradation of the organic dye Rhodamine B RhB under ultrasonic vibration. The synthesis of NKxBT nanopowders was conducted using the sol-gel autocombustion method. Coupled structural analysis reveals the presence of an intermediate Morphotropic Phase Boundary (MPB, where two phases coexist) in the optimal NK15BT composition. The piezocatalytic degradation results showed a total piezo-degradation in only 90 min and a rate constant 8 times higher than the undoped NK0BT. The enhanced piezocatalytic activity results from a synergistic effect of MPB presence, reduced particle size, optimal bandgap and high
lattice strain. The NK15BT sample also demonstrated good reusability and good mineralization.
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All authors Salma Ayadh, Salma Touili, Mbarek Amjoud, Daoud Mezzane, Mohamed Goune, Jaafar Ghanbaja, Manal Benyoussef, Hana Ursic, Nejc Suban, Mustapha Raihane, Zdravko Kutnjak, Mimoun El Marssi
Materials Science
Two-dimensional alternating ferrimagnetism with strain-controlled half-metallic state and valley polarization
W. Z. Zhuo, Z. H. Guan, Z. L. Peng et al. (+4 more)
The discovery of altermagnetism offers new opportunities for exploring novel
quantum states and developing spintronic devices for enabling momentum dependent
spin splitting in compensated systems, while zero net magnetization limit its manipulability using conventional
magnetic method. Here, we propose 2D alternating ferrimagnetism,a phase merging alternating momentum dependent
spin splitting with a finite net magnetization. A tight binding model reveals that alternating ferrimagnetism originates from uncompensated magnetization in altermagnets, facilitating concurrent net magnetization and alternating
spin splitting. First principles calculations and Monte Carlo simulations demonstrate stable alternating ferrimagnetism in strained and Cr substiting V2Te2O, which exhibit strain tunable net magnetization, reversable half
metallicity and valley polarization, accompanied by long range
magnetic order above room temperature. By combining altermagnetic and
ferromagnetic properties, alternating ferrimagnetism expand the 2D magnetism landscape and offer pathways for energy efficient spintronic applications.
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All authors W. Z. Zhuo, Z. H. Guan, Z. L. Peng, Y. N. Pan, J. Chen, Y. Yang, M. H. Qin
Materials Science
Photoemission intermittency via stochastic gating in rubrene nanowires coupled to plasmonic silver nanoparticles
Moha Naeimi, Waqas Pervez, Frithjof Harmsen et al. (+2 more)
In this work, we report a new nanoscale phenomenon observed as photoemission intermittency (On-Off electron emission), manifested as
stochastic bursts in electron yield at quasi-one-dimensional organic wires and silver nanoparticles interface. Energy-resolved measurements reveal that the emitted electrons carry out hybrid information, containing photoelectron yield enhancement associated with the nanoparticles and kinetic energies determined by the organic
semiconductor. The intermittency results in a dynamic shift of the electron spectra correlating with the photoelectron yield. We attribute the observed behaviour to the photo-hole accumulation and
stochastic gating of charge due to electron-hole separation at the nano interface. These findings introduces the photoemission intermittency as a nanoscale phenomenon indicating a new dynamic regime of charge assisted emission at organic-plasmonic interfaces. Keywords: rubrene, nanoparticle, PEEM,
exciton, charge
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All authors Moha Naeimi, Waqas Pervez, Frithjof Harmsen, Ingo Barke, Sylvia Speller
Materials Science
Quanchao Du, Zhenlong Zhang, Yuanjun Jin et al. (+7 more)
Odd-parity magnetism represents an intriguing frontier in unconventional magnets; however, its realization has traditionally relied on noncollinear
magnetic orders accompanied by broken
spin conservation, which inevitably causes
spin relaxation and dissipative transport of
spin-encoded information. Here, we uncover a distinct route toward
spin-conserving odd-parity
magnon splitting enabled by antichiral Haldane-like flux (AHF) in collinear
antiferromagnetic multiferroics.
Symmetry analysis reveals that such AHF driven by intra-sublattice Dzyaloshinskii-Moriya interactions (DMI) gives rise to
symmetry-dependent odd-parity
magnon splittings, ranging from $p$-wave and $f$-wave to nodeless forms. Moreover, the coupling between ferroelectric modes and DMI provides an electric-field knob for manipulating
chiral band splitting and
magnon transport. Combining density functional theory (DFT) calculations, we identify a series of promising candidate materials in both 2D and bulk
antiferromagnetic multiferroics. Our work provides new insights into the realization of odd-parity
chiral magnons in collinear antiferromagnets and magnetoelectric coupling mechanisms in multiferroics.
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All authors Quanchao Du, Zhenlong Zhang, Yuanjun Jin, Rui Li, Haibo Xie, Zhe Wang, Zhijun Jiang, Lei Zhang, Hongjian Zhao, Jinyang Ni
Materials Science · Cross-listed from cond-mat.str-el
Equilibrium Stabilization of a Hidden Phase Like Metallic State in 1T-TaS2
Anil Rajapitamahuni, Suji Park, Houk Jang et al. (+3 more)
Electronic phases that lie outside the
equilibrium ground state offer a route to explore competing configurations in correlated materials. In 1T-TaS2, ultrafast excitation accesses a metallic hidden phase that is distinct from the commensurate insulating ground state. Here we use angle-resolved photoemission spectroscopy to show that an equivalent electronic configuration is stabilized in exfoliated intermediate-thickness 1T-TaS2 flakes, where it persists up to room temperature before evolving through a different sequence of electronic transitions. This
equilibrium hidden-phase-like state hosts a metallic band with finite
Fermi-level spectral weight while retaining the characteristic hybridization gaps associated with the
star-of-David band folding. These results establish a platform for controlling competing electronic states in layered materials, with implications for both
quantum science and phase change technologies.
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All authors Anil Rajapitamahuni, Suji Park, Houk Jang, Asish K. Kundu, Elio Vescovo, Turgut Yilmaz
Materials Science
Enrichment of rhombohedral stacking by mechanical exfoliation of graphite
Krisztián Márity, Konrád Kandrai, Gergely Dobrik et al. (+5 more)
Rhombohedral (ABC) graphite hosts a surface-localized flat band that supports correlated and topological electronic phases, but its experimental study is limited by the scarcity of ABC stacking in natural graphite, which is dominated by Bernal (AB) stacking. Here we show that the routine mechanical exfoliation step itself enriches the rhombohedral content of graphite flakes, and that a simple blade-assisted exfoliation step, which introduces additional shear, amplifies the effect further. Using large-area Raman 2D-band skewness mapping we measure ABC content at area fractions of 3% in the pristine source
crystal, 16% after conventional exfoliation, and 26% after blade-assisted exfoliation for thick flakes. In thin flakes ($<20$ layers) the per-flake area fraction reaches 75% in the upper tail of the distribution. Tracking individual flakes before and after blade-assisted exfoliation shows that wrinkles seed AB-ABC domain walls, and uniaxial strain can move these walls. Blade-assisted mechanical exfoliation therefore removes one of the bottlenecks to the preparation of ABC-rich graphite samples for studies of correlated and topological phases in rhombohedral graphite.
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All authors Krisztián Márity, Konrád Kandrai, Gergely Dobrik, Zsolt E. Horváth, Kristóf Németh Dániel, György Kálvin, Levente Tapasztó, Péter Nemes-Incze
Materials Science · Cross-listed from physics.app-ph
Simultaneously monitoring Ga adsorption and desorption kinetics on GaN(0001) using four in situ techniques
Huaide Zhang, Philipp John, Jingxuan Kang et al. (+3 more)
We present a systematic investigation of Ga adsorption and desorption kinetics on the wurtzite GaN(0001) surface using four in situ techniques operated simultaneously: reflection high-energy electron diffraction,
laser reflectometry, line-of-sight quadrupole mass spectrometry, and optical pyrometry. Flux- and temperature-dependent experiments are performed for Ga coverages ranging from the submonolayer to the droplet regime. Despite their distinct transient responses, the signals from all four techniques and their trends with surface coverage are quantitatively reproduced by a unified kinetic model of Ga adsorption,
diffusion, and desorption. An Arrhenius analysis of the Ga adlayer desorption yields an activation energy of (2.87 $\pm$ 0.04) eV.
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All authors Huaide Zhang, Philipp John, Jingxuan Kang, Lutz Geelhaar, Yongjin Cho, Oliver Brandt
Materials Science
Virp: neural network-accelerated prediction of physical properties in site-disordered materials
Andy Paul Chen, Martin Hoffmann Petersen and Kedar Hippalgaonkar
Among metallic
alloys, ceramics, and even common compounds such as water ice, it is usual to find materials in which crystalline order is expressed as a probability. In such cases, one or more sites within a
crystal can be occupied by multiple elements or vacancies, according to a set of probabilities. These
crystal structures remain inaccessible to common first-principles materials simulation methodologies, which assumes perfect
crystal order. Workaround strategies to this limitation include quasirandom structures and cluster expansion. These methods are system-specific and computationally expensive as they rely on large scale Monte Carlo simulations of enlarged unit
cells. To address these limitations, we propose a pipeline combining a permutation-based virtual
cell generation
algorithm, sampling regime, and thermodynamic post-processing which greatly improves the feasibility of computation analyses for site-disordered materials. We demonstrate that the massive configurational space can be adequately sampled with 400 virtual
cells, as long as the supercell definition is sufficiently large.
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Materials Science
Delineating the interplay effects of microstructure topology and residual stresses in ultrafast laser irradiated thin films
Hariprasath Ganesan and Stefan Sandfeld
Advanced nanodevices require high-precision machining of thin films using ultrafast
lasers. However, thin-film fabrications cause variations in microstructure, crystallographic orientation, and residual stresses owing to coating conditions and substrate choice. This work investigates the complex interplay between these factors in ultrafast
laser-irradiated gold (Au) thin films using a hybrid Two Temperature Model-Molecular Dynamics simulations. We realized microstructure-informed atomistic models with varying grain
topologies (randomized vs. equiaxed), grain sizes, and residual tensile/compressive stress configurations. Our results reveal a clear hierarchy of influence on
laser-metal interaction: 1.) Microstructure configuration 2.)
Topology 3.) Grain Size 4.) Crystallographic orientations. In fine-grained thin films, grain boundaries act as primary melting precursors, while local crystallographic orientation determines the melting extent in coarser grains. Residual tensile stresses contribute to higher melting and greater
laser-induced expansion than unstrained films. Conversely, residual compressive stresses resist deformation, as deposited thermal energy is utilized to overcome
lattice compression, leading to reduced expansion. We found that microstructure grain
topology and size exert a stronger fingerprint on film expansion than the initial defect density.
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Materials Science
Toward the Rational Design of Molecular Field-Coupled Nanocomputing Candidates
Federico Ravera, Leonardo Medrano Sandonas, Andrea Vezzoli et al. (+4 more)
Molecular Field-Coupled Nanocomputing (MolFCN) is a promising beyond-CMOS paradigm in which information is propagated electrostatically rather than through charge transport, enabling ultra-low-power logic. Identifying molecules with stable logic states, efficient clock-field switching, and reliable information propagation, however, remains an open challenge. In this Letter, we introduce LUFFY (Layered Unified Framework for MolFCN systematic analYsis), a framework for the rational design and validation of molecular candidates for MolFCN architectures. Starting from 27 synthetically accessible molecules, we combine conformational sampling and electrostatic analysis in neutral and oxidized states to derive robust descriptors of molecular response. In particular, we extract the V${in}$-to-Aggregated-Charge Transcharacteristics (VACTs), capturing the field-induced charge response, and introduce energy-averaged models validated via ab initio molecular dynamics to account for conformational diversity. Finally, we use the resulting molecular responses to evaluate device-level propagation and demonstrate stable information transfer. These results directly link molecular structure to functional information flow, identifying conformationally robust electrostatic response as a key requirement for MolFCN operation. Overall, this work establishes a unified and transferable framework for the identification and validation of MolFCN molecular candidates, bridging molecular design and
circuit-level functionality. By unifying previously fragmented approaches into a sustainable methodology, LUFFY enables rational and scalable molecular discovery and establishes a foundation for data-driven design strategies that accelerate the development of ultra-low-power information processing technologies.
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All authors Federico Ravera, Leonardo Medrano Sandonas, Andrea Vezzoli, Yuri Ardesi, Mariagrazia Graziano, Gianluca Piccinini, Gianaurelio Cuniberti
Materials Science
High-throughput study of electrical conductivity in ordered metals
Thalis H. B. da Silva, Hai-Chen Wang, Tiago F. T. Cerqueira et al. (+3 more)
We present a computational framework that integrates machine learning with high-throughput ab initio calculations to screen over 2.8 million compounds for metallic transport. We identify several intermetallic candidates with predicted high conductivities comparable to that of aluminum (36.59 x $10^6$ S/m). We perform full electron-
phonon coupling calculations for the top-performing materials, yielding results in good agreement with available experimental data. Our analysis reveals that while the noble metals (Ag, Au, Cu) possess a conductivity that remains difficult to surpass due to their unique electronic structure and low scattering, compounds like LiBePt2 can achieve comparable performance by utilizing valence electrons from light elements to shift high-scattering d-states beneath the
Fermi level. This study not only identifies novel high-performance conductors but also demonstrates the predictive power of combining statistical learning with detailed ab initio calculations.
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All authors Thalis H. B. da Silva, Hai-Chen Wang, Tiago F. T. Cerqueira, Simone Di Cataldo, Silvana Botti, Miguel A. L. Marques
Materials Science
Theory-Guided, Machine-Learning-Accelerated Discovery of a 3D Carbon Nested Nodal-Surface Semimetal
Shuaihua Zhang, Silei Guo, Jingxiang Liu et al. (+3 more)
Extending the Dirac physics of two-dimensional (2D)
graphene into three dimensions (3D) carbon allotropes with higher-dimensional band degeneracies remains a central challenge in topological materials science. Here, we propose a general
symmetry-engineering principle that systematically transforms
graphene's Dirac cone into a 3D nodal surface via controlled layering and registry shift, and employ this principle to guide a machine-learning-accelerated inverse design. By integrating a
crystal diffusion variational autoencoder(CDVAE) with a
Crystal Transformer, we discover a novel, dynamically and mechanically stable carbon allotrope named Netsene (bct-C$_{24}$), which crystallizes in the body-centered tetragonal I4/mcm space group. First-principles calculations confirm that Netsene is a unique nested nodal-surface semimetal: it hosts a complex, double-bowl-shaped nodal-surface system around the
Fermi level, protected by non-symmorphic
symmetries, alongside Dirac-like linear crossings with
Fermi velocities comparable to
graphene ($\sim 9 \times 10^5$~m/s). Its non-trivial bulk
topology manifests in drumhead surface states, including a nearly flat band. Netsene provides a structurally robust, bulk platform that unifies ultrahigh carrier mobility, topological nodal surfaces, and potential correlation physics, demonstrating the power of theory-guided, machine-learning-accelerated discovery for engineering topological
quantum phases.
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All authors Shuaihua Zhang, Silei Guo, Jingxiang Liu, Baoxin Hu, Yanling Wu, Jun Li
Materials Science
CNN-Based Classifier for Automated Identification of Magnetic States in Spin Dynamics Simulations
Amal Aldarawsheh, Ahmed Alia and Stefan Blügel
The identification and classification of different
magnetic states are essential for understanding the complex behavior of
magnetic systems. Traditional approaches that rely on handcrafted features or manual inspection often fall short, particularly when dealing with subtle or topologically complex
spin textures. In this study, we present an automated deep learning model that employs an EfficientNetV1B0 Convolutional Neural Network to classify nine distinct
magnetic states, including both
ferromagnetic (FM) and
antiferromagnetic (AFM)
spin textures such as AFM skyrmions and AFM stripe domains. The
spin configurations are generated through atomistic
spin dynamics simulations using the Spirit code, then visualized with VFRendering to produce RGB images, which serve as inputs to the classification model.
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Materials Science · Cross-listed from physics.comp-ph
A path-finding algorithm for computing minimal-weight-matching centrosymmetry parameter
Vasily V. Pisarev
In 2020, Peter Larsen reported flaws in the methods for centrosymmetry parameter computation in the existing molecular dynamics and analysis packages. He proposed an intuitive an mathematically rigorous formulation for centrosymmetry parameter in terms of minimal-weight matching (MWM) on a fully-connected graph of atomic neighbors. He proposed using Edmonds' blossom
algorithm for computing such a matching. In this paper, we investigate an alternative
algorithm for MWM CSP computation using path finding approach and A*
algorithm.
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Materials Science
High-field Magnetotransport Studies of Surface Conducting Diamonds
Kaijian Xing, Daniel L. Creedon, Golrokh Akhgar et al. (+5 more)
The observation of strong and tunable
spin-orbit interaction (SOI) in surface conducting diamond opens up a new avenue for building diamond-based spintronics. Herein we provide a comprehensive method to analyze the magnetotransport behavior of surface conducting hydrogen-terminated diamond (H-diamond)
Hall bar devices and Al/Al2O3/V2O5/H-diamond MOSFETs, respectively. By adopting a significantly improved theoretical magneto transport model, the reduced magnetoconductance can be accurately explained both within and outside the
quantum diffusive regime. The model is valid for all doping strategies of surface conducting diamond tested. From this analysis, we find that the orbital magnetoresistance, a classical effect distinct from the SOI, dominates the magnetotransport in surface conducting diamond at high
magnetic fields. Furthermore, local hole mobilities as high as 1000 ~ 3000 cm2/Vs have been observed in this work, indicating the possibility of diamond-based electronics with ultra-high hole mobilities at cryogenic temperatures.
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All authors Kaijian Xing, Daniel L. Creedon, Golrokh Akhgar, Steve A. Yianni, Jeffrey C. McCallum, Lothar Ley, Dong-Chen Qi, Christopher I. Pakes
Materials Science
First-Principles Study of Fe Adsorption and Its Effects on the Mechanical and Electrical Properties of Monolayer and Bilayer Biphenylene Networks
Xiao-Ke Zhang and Zheng-Zhe Lin
BPN is a 2D carbon allotrope that exhibits promising potential for applications across a wide range of fields. In this work, we systematically investigated the adsorption characteristics of Fe atoms on monolayer and
bilayer BPN using first-principles calculations. Structural optimization and adsorption energy analysis reveal that, for monolayer BPN, the adsorption strength gradually enhances with increasing Fe coverage, indicating a strengthening of Fe-substrate interactions. An Fe/C ratio of 50% corresponds approximately to completion of the first Fe adsorption layer on the BPN surface. For
bilayer BPN, the energetically preferred adsorption site for Fe atom is located at the center of the interlayer four-membered ring, with an average adsorption energy of -4.3 eV. Mechanical properties are further evaluated for pristine and Fe-decorated BPN. The results demonstrate that monolayer and
bilayer BPN possess relatively high in-plane Young's and shear
moduli, indicative of excellent in-plane mechanical stability. For monolayer BPN, Fe adsorption has only a limited effect on the in-plane mechanical response at low coverages, whereas a noticeable enhancement in stiffness emerges at higher Fe loadings. In contrast, the out-of-plane mechanical response of
bilayer BPN is significantly affected by Fe incorporation. The effective out-of-plane elastic constant C33 of pristine
bilayer BPN is calculated to be 24.59 GPa, indicating relatively weak interlayer interactions and facile deformation along the out-of-plane direction. Notably, this property can be substantially enhanced by interlayer Fe adsorption, with C33 increasing dramatically to 515.63 GPa upon an Fe/C ratio of 25 %. The transport calculations reveal pronounced anisotropy in the conductivity normalized by the relaxation time {\sigma} / {\tau}, with markedly different values along the two in-plane crystallographic directions.
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Materials Science
Optical anisotropy and electronic states in the pleochroic material Ca$_3$ReO$_5$Cl$_2$
Takumi Tsukihara, Ibuki Terada and Michi-To Suzuki
Pleochroism is a type of optical anisotropy in which the apparent color of a material varies depending on the polarization and propagation direction of incident light. The oxychloride compound Ca$_3$ReO$_5$Cl$_2$ has recently attracted
attention due to its pronounced pleochroism. The paramagnetic state of this compound, characterized by localized Re 5$d$ electrons, is challenging to describe within conventional first-principles methods. In this study, we investigate the optical anisotropy in Ca$_3$ReO$_5$Cl$_2$ using first-principles calculations, with particular focus on the relationship between the optical spectra and electronic states. We employ a ferromagnetically ordered state to effectively capture the localized character of the Re 5$d$ electrons. The calculated dielectric function and absorption coefficient qualitatively reproduce the experimentally observed peak structures. An orbital-resolved analysis indicates that the characteristic optical transitions associated with the pleochroism predominantly involve Re-$d$-dominated electronic states, highlighting the key role of the Re $d$ electrons in the pleochroic optical response of Ca$_3$ReO$_5$Cl$_2$.
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Materials Science · Cross-listed from cond-mat.str-el
Effect of Pb Substitution at the Mo site on the Magnetic Properties of the Polar Magnet Fe$_2$Mo$_3$O$_8$
Takumi Shirasaki, Taichi Ishikawa, Shungo Nakayama et al. (+1 more)
The ternary transition-metal
oxide Fe$_2$Mo$_3$O$_8$ is a polar magnet characterized by a layered structure of
magnetic Fe honeycomb
lattices and non-
magnetic Mo kagome
lattices. Whereas previous studies have primarily focused on the chemical substitution at the Fe sites to modulate the
magnetic properties, the Mo sites have remained largely unexplored due to the strong
spin-singlet trimerization of Mo$^{4+}$ ions. In this study, we investigated the effect of substituting non-
magnetic Pb$^{4+}$ and Zr$^{4+}$ ions into the Mo sites to intentionally disrupt the Mo trimers. Our results reveal that the disruption of the Mo
spin-singlet state induces active
spins within the Mo layer, resulting in the emergence of a
ferromagnetic-like behavior that persists even at room temperature. Quantitative analysis that takes into account the weight fraction of the main phase suggests an effective
spin $S = 1/2$ state per active Mo ion upon trimer disruption. These findings demonstrate that controlling non-
magnetic cluster states within a polar host via chemical substitution is a promising approach for designing room-temperature magnetoelectric materials.
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All authors Takumi Shirasaki, Taichi Ishikawa, Shungo Nakayama, Hideki Kuwahara