Peer Revenue Play credits. Real papers.

Papers

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

Physics Condensed Matter Materials Science

cond-mat.mtrl-sci Watch Materials Science

Wednesday 17 December

Materials Science

Atomically-precise synthesis and simultaneous integration of 2D transition metal dichalcogenides enabled by nano-confinement

Ce Bian, Yifan Zhao, Roger Guzman et al. (+15 more)

Two-dimensional (2D) materials, such as graphene, transition metal dichalcogenides (TMDs), and hBN, exhibit intriguing properties that are sensitive to their atomic-scale structures and can be further enriched through van der Waals (vdW) integration. However, the precise synthesis and clean integration of 2D materials remain challenging. Here, using graphene or hBN as a vdW capping layer, we create a nano-confined environment that directs the growth kinetics of 2D TMDs (e.g., NbSe2 and MoS2), enabling precise formation of TMD monolayers with tailored morphologies, from isolated monolayer domains to large-scale continuous films and intrinsically-patterned rings. Moreover, Janus S-Mo-Se monolayers are synthesized with atomic precision via vdW-protected bottom-plane chalcogen substitution. Importantly, our approach simultaneously produces ultraclean vdW interfaces. This in situ encapsulation reliably preserves air-sensitive materials, as evidenced by the enhanced superconductivity of nano-confined NbSe2 monolayers. Altogether, our study establishes a versatile platform for the controlled synthesis and integration of 2D TMDs for advanced applications.
Read the full abstract

All authors Ce Bian, Yifan Zhao, Roger Guzman, Hongtao Liu, Hao Hu, Qi Qi, Ke Zhu, Hao Wang, Kang Wu, Hui Guo, Wanzhen He, Zhaoqing Wang, Peng Peng, Zhiping Xu, Wu Zhou, Feng Ding, Haitao Yang, Hong-Jun Gao

Materials Science

Machine-learned accelerated discovery of oxidation-resistant NiCoCrAl high-entropy alloys

Dennis Boakye and Chuang Deng

The development of oxidation-resistant high-entropy alloy (HEA) bond coats is restricted by the limited understanding of how multi-principal element interactions govern scale formation across temperatures. This study uncovers new oxidation trends in NiCoCrAl HEAs using a data-driven analysis of high-fidelity experimental oxidation data. The results reveal a clear temperature-dependent transition between alumina- and chromia-dominated protection, identifying the compositional regimes where alloys rich in Al dominate at $\ge1150$ {\deg}C, mixed Al-Cr chemistries are optimal at intermediate temperatures, and, unexpectedly, Cr-rich low-Al alloys perform best at 850 {\deg}C-challenging the assumption that high Al is universally required. The effects of Hf and Y are shown to be strongly composition-dependent with Hf producing the largest global reduction in oxidation rate, while Y becomes effective primarily in NiCo-lean alloys. Y-Hf co-doping offers consistent improvement but exhibits site-saturation behavior. These insights identify new high-performing HEA bond-coat families, including $\mathrm{Ni_{17}Co_{23}Cr_{30}Al_{30}}$ as a substitute for conventional mutlilayer thermal barrier coatings.
Read the full abstract

Materials Science

Electromechanical properties of the 180{\deg} domain wall in PbTiO3

I. Rychetsky, A. Klic and W. Schranz

We analyze the electromechanical response of the 180 degree ferroelectric domain wall in tetragonal PbTiO3 by combining first-principles calculations with a Landau-Ginzburg-Devonshire (LGD) description. Using regular multidomain structures with varying domain-wall density, we extract polarization profiles and lattice distortions and map them onto the continuum model to determine conventional (homogeneous) and gradient (inhomogeneous) electrostriction. Conventional electrostriction yields only a small negative length change of the sample, whereas gradient electrostriction–arising from the coupling between strain and polarization gradients–produces a positive contribution nearly an order of magnitude larger and localized at the wall core. Our results demonstrate that gradient electrostriction dominates the electromechanical response of 180 degree walls in PbTiO3, supporting its inclusion in LGD models that stabilize Bloch-type domain wall structures.
Read the full abstract

Materials Science

Thermal Stabilization of Defect Charge States and Finite-Temperature Charge Transition Levels

Tobias Hainer, Ethan Berger, Esmée Berger et al. (+3 more)

Point defects introduce localized electronic states that critically affect carrier trapping, recombination, and transport in functional materials. The associated charge transition levels (CTLs) can depend on temperature, requiring accurate treatment of vibrational and electronic free-energy contributions. In this work, we use machine-learned interatomic potentials to efficiently compute temperature-dependent CTLs for vacancies in MgO, LiF, and CsSnBr3. Using thermodynamic integration, we quantify free-energy differences between charge states and calculate the vibrational entropy contributions at finite temperatures. We find that CTLs shift with temperature in MgO, LiF and CsSnBr3 from both entropy and electronic contributions. Notably, in CsSnBr3 a neutral charge state becomes thermodynamically stable above 60 K, introducing a temperature-dependent Fermi-level window absent at 0 K. We show that the widely used static, zero-kelvin defect formalism can miss both quantitative CTL shifts and the qualitative emergence of new stable charge states.
Read the full abstract

All authors Tobias Hainer, Ethan Berger, Esmée Berger, Olof Hildeberg, Paul Erhart, Julia Wiktor

Materials Science · Cross-listed from physics.optics

Towards coherent polaritonic circuits operating at room temperature

Addhyaya Sharma, Ezra Bader, Ravindra K. Yadav et al. (+6 more)

Polariton condensation is a potential system state for performing analog computations, given that it exhibits quantum behavior at macroscopic scales readily probed with low-cost optical methods. Current methods of fabricating devices in polariton microcavities largely involve patterning the devices via e-beam lithography before the cavity is completed, which offers less flexibility in device creation and reduces the maximum possible refractive index contrast. Moreover, the momentum and spatial distributions of the condensate are highly dependent on the host platform, and it has been difficult to preserve the desired behavior when modifying a given cavity. Here we introduce a method that addresses both of these challenges with the creation of polaritonic circuits of arbitrary forms etched via Focused Ion Beam into an organic microcavity based on Rhodamine 3B Perchlorate within a Small Molecule Ionic Isolation Lattices complex. We demonstrate room temperature condensation and propagation of polaritons in rectangular and trapezoidal waveguides by analyzing spatial and angle-resolved photoluminescence. We also discuss the blue-shifting and non-zero momentum of the condensate and show that it is strongly confined up to several higher energy levels. As an example, we report the spatial profiles of condensation in custom devices, such as a ring waveguide, a Y-splitter, and a Mach-Zehnder interferometer. This work represents a first step towards the realization of more complex, fully integrated, coherent polaritonic circuits operating at room temperature.
Read the full abstract

All authors Addhyaya Sharma, Ezra Bader, Ravindra K. Yadav, Juan Carlos Obeso Jureidini, Michael Reitz, Daegwang Choi, Rishabh Kaurav, Joel Yuen-Zhou, Vinod M. Menon

Materials Science

Lithium-ion battery degradation: Introducing the concept of reservoirs to design for lifetime

Mohammed Asheruddin Nazeeruddin, Ruihe Li, Simon E. J. OKane et al. (+2 more)

Designing lithium-ion batteries for long service life remains a challenge, as most cells are optimized for beginning-of-life metrics such as energy density, often overlooking how design and operating conditions shape degradation. This work introduces a degradation-aware design framework built around finite, interacting reservoirs (lithium, porosity, and electrolyte) that are depleted over time by coupled degradation processes. We extend a physics-based Doyle-Fuller-Newman model to include validated mechanisms such as SEI growth, lithium plating, cracking, and solvent dry-out, and simulate how small design changes impact lifetime. Across more than 1,000 cycles, we find that increasing electrolyte volume by just 1% or porosity by 5% can extend service life by over 30% without significantly affecting cell energy density. However, lithium excess, while boosting initial capacity, can accelerate failure if not supported by sufficient structural or ionic buffers. Importantly, we show that interaction between reservoirs is crucial to optimal design: multi-reservoir tuning yields either synergistic benefits or compound failures, depending on operating conditions. We also quantify how C-rate and operating temperature influence degradation pathways, emphasizing the need for co-optimized design and usage profiles. By reframing degradation as a problem of managing finite internal reservoirs, this work offers a predictive and mechanistic foundation for designing lithium-ion batteries that balance energy, durability, and application-specific needs.
Read the full abstract

All authors Mohammed Asheruddin Nazeeruddin, Ruihe Li, Simon E. J. OKane, Monica Marinescu, Gregory J. Offer

Materials Science

Ultrafast Strongly Anisotropic Valleytronics in SnSe

Yiming Pan, Sotirios Fragkos, Dominique Descamps et al. (+3 more)

Valleytronics aims to control electrons in a valley-specific manner for quantum information manipulation. Due to their strong in-plane anisotropy, which enables polarization-controlled optical transitions to distinct nondegenerate valleys, group-IV monochalcogenides have been recently proposed as promising candidates for next-generation valleytronic materials. However, ultrafast nonequilibrium dynamics following optical preparation of valley-polarized states remain completely unexplored in these systems. Combining time- and angle-resolved extreme-ultraviolet photoemission spectroscopy with time-dependent Boltzmann equation simulations, we investigate ultrafast valley polarization dynamics following polarization-controlled photoexcitation in SnSe. We show that selective excitation to valleys at global conduction minima yields nearly unity and time-independent valley polarization. In contrast, photoexcitation to the other valley channel leads to ultrafast decay and reversal of valley polarization on sub-picosecond timescales due to intervalley scattering mediated by strong electron-phonon coupling with an optical phonon mode. Our findings reveal strongly anisotropic and radically different nonequilibrium valley physics than in most common two-dimensional valleytronics materials.
Read the full abstract

All authors Yiming Pan, Sotirios Fragkos, Dominique Descamps, Stéphane Petit, Fabio Caruso, Samuel Beaulieu

Materials Science · Cross-listed from physics.optics

Integrated on-chip quantum light sources on a van der Waals platform

Pietro Metuh, Paweł Wyborski, Athanasios Paralikis et al. (+4 more)

Scalable photonic quantum information technologies require a platform combining quantum light sources, waveguides, and detectors on a single chip. Here, we introduce a van der Waals platform comprising strain-engineered bilayer WSe$_2$ quantum emitters, integrated on multimode WS$_2$ waveguides with grating couplers, enabling efficient on-chip quantum light sources. The emitters exhibit bright, highly polarised emission that couples efficiently into WS$_2$ waveguides. Under discrete-state excitation, we observe high-purity, waveguide-coupled single-photon emission, measured using both single-port and cross-correlated, multi-port photon streams, yielding $g^{(2)}(0) = 0.003^{+0.030}_{-0.003}$ and $g^{(2)}(0) = 0.076\pm0.023$, respectively. For a single output, the out-coupled single-photon count rate at the first lens reaches approximately 357 kHz under continuous-wave discrete-state excitation, corresponding to an estimated minimum waveguide-coupled rate of 1.68 MHz. These results demonstrate an efficient, integrated single-photon source and establish a pathway toward scalable photonic quantum information processing centred around nanoengineered van der Waals materials.
Read the full abstract

All authors Pietro Metuh, Paweł Wyborski, Athanasios Paralikis, Frederik Schröder, Nicolas Stenger, Niels Gregersen, Battulga Munkhbat

Materials Science

Automatic generation of input files with optimised k-point meshes for Quantum Espresso self-consistent field single point total energy calculations

Elena Patyukova, Junwen Yin, Susmita Basak et al. (+3 more)

Performing density functional theory (DFT) calculations requires a careful choice of computational parameters to ensure convergence and obtain meaningful results. This represents a particularly important problem for high-throughput and agentic workflows, where due to computational cost, any additional convergence studies are preferably to be avoided. So, there is a need for tools and models which are able to predict DFT parameters from basic input information, such as a structure. In this work, we develop a machine learning approach to predict the appropriate k-point sampling in DFT calculations and generate the input files for Quantum Espresso self-consistent field calculations. To achieve this, we first generated a training dataset comprising over 20,000 materials, each with an energy convergence threshold of 1 meV/atom. Several ML models were evaluated for their ability to predict k-points distance, and uncertainty estimation was incorporated to guarantee that, for at least 85-95% of compounds, the predicted k-distance lies within the convergence region. The best-performing models are made publicly available through an open-access web application.
Read the full abstract

All authors Elena Patyukova, Junwen Yin, Susmita Basak, Samuel Pinilla Sanchez, Alin Elena, Gilberto Teobaldi

Materials Science

Defect Tolerance and Local Structural Response to 3d Transition-Metal Substitution in CsPbI3

Misbah Shaheen and Sheharyar Pervez

We present a systematic first-principles study of substitutional 3d transition-metal (TM) defects in CsPbI3 using the spin-polarized GGA+U framework. TM incorporation is generally energetically favorable and induces lattice distortions that are strongly localized around the defect site, preserving the overall structural integrity of the host. Analysis of defect formation energies and electronic structure shows that, with the exception of Sc and Ti, CsPbI3 exhibits a strong resistance to deep trap formation. Most TM substitutions instead introduce resonant states that hybridize with the band edges, consistent with the defect-tolerant nature of the material. While these states can modify the band gap, they do not generate isolated mid-gap traps. The observed distortions arise from strain-driven Van Vleck modes governed by ionic-radius mismatch, electronegativity differences, and TM-I orbital overlap, with amplitudes that decay rapidly away from the defect. Spin-polarized calculations reveal significant TM-induced spin polarization on the ligands and, in some cases, on neighboring Pb atoms, reflecting variations in covalency and hybridization across the 3d series. Together, these results establish a unified picture in which local structural response, electronic hybridization, and spin polarization jointly control the stability and electronic impact of TM defects in CsPbI3 , identifying dopants that are electronically benign or detrimental.
Read the full abstract

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

Ab initio insights into plasmonic and strong-field contributions to H$_2$ dissociation on silver nanoshells

Natalia E. Koval, J. Iñaki Juaristi and Maite Alducin

Modeling plasmonic catalysis by applying femtosecond laser pulses of high intensity ($10^{13}-10^{15}$ W cm$^{-2}$), although justified by the time-dependent density functional theory (TDDFT) time-scale limitations, can lead to a dissociation mechanism that is completely unrelated to the plasmon excitation created under low-intensity continuous light in experiments (on the order of 1 W cm$^{-2}$). In this study, we examine the dissociation of H$_2$ on a large octahedral Ag nanoshell under varying field intensity, frequency, and duration, and we explore the possibility of identifying optimal modeling conditions accessible with current TDDFT simulations. We show that using this large nanoshell that consists in the outer layer of the Ag$_{231}$ cluster, it is still possible to disentangle the role of the plasmon from strong-field effects at applied field intensities as high as $(2-8) \times 10^{13}$ W cm$^{-2}$. In particular, although strong-field effects are always present at these intensities, we find that the excited plasmon dominates the dissociation process at the lowest applied intensity of $2 \times 10^{13}$ W cm$^{-2}$. Furthermore, at the highest intensity, at which strong-field effects become dominant, the plasmon contributes to accelerating the dissociation of the molecule. Overall, our simulations pave the way to bridge the intensity gap between TDDFT modeling and experiments in plasmonic catalysis.
Read the full abstract

Materials Science

CO on a Rh/Fe3O4 single-atom catalyst: high-resolution infrared spectroscopy and near-ambient-pressure scanning tunnelling microscopy

Nail El Hocine Barama, Chunlei Wang, Panukorn Sombut et al. (+14 more)

Infrared reflection absorption spectroscopy (IRAS) offers a powerful route to bridging the materials and pressure gaps between surface science and powder catalysis. Using a newly developed IRAS setup optimised for dielectric single crystals, we investigate CO adsorption on the model single-atom catalyst Rh/Fe3O4(001). IRAS resolves three species: monocarbonyls at isolated, twofold-coordinated Rh adatoms, monocarbonyls at fivefold-coordinated Rh atoms embedded in the surface, and gem-dicarbonyls at isolated, twofold-coordinated Rh adatoms. Under ultra-high vacuum (UHV) conditions, RhCO monocarbonyl species at adatom sites dominate. Rh(CO)2 gem-dicarbonyl formation is kinetically hindered and occurs predominantly through CO-induced dissociation of Rh dimers rather than sequential adsorption of two CO molecules at an isolated, twofold Rh adatom. The sequential-adsorption pathway to Rh(CO)2 becomes accessible at millibar CO pressures as evidenced by near-ambient-pressure scanning tunnelling microscopy (NAP-STM). These findings link the UHV behaviour to that expected under realistic reaction conditions. Assignments of the vibrational frequencies to individual species rely on isotopic labelling, thermal treatments, and a review of previous SPM, XPS, and TPD data, supported by density functional theory (DFT)-based calculations. While theory provides qualitative insight, such as the instability of dicarbonyls on fivefold-coordinated Rh atoms, it does not yet reproduce experimental frequencies quantitatively and is sensitive to the computational parameters, highlighting the need for robust experimental benchmarks. The spectroscopic fingerprints established here provide a reliable foundation for identifying Rh coordination environments in oxide-supported single-atom catalysts.
Read the full abstract

All authors Nail El Hocine Barama, Chunlei Wang, Panukorn Sombut, David Rath, Adam Lagin, Martin Ormos, Lena Puntscher, Faith J. Lewis, Zdenek Jakub, Florian Kraushofer, Moritz Eder, Matthias Meier, Michael Schmid, Ulrike Diebold, Cesare Franchini, Peter Matvija Jirí Pavelec, Gareth S. Parkinson

Materials Science

Magnetoconductance evolution across the topological-trivial phase transition in ${In_{x}}({Bi_{0.3}}{Sb_{0.7}})_{2-x}{Te_3}$ thin films

Sambhu G Nath, Subhadip Manna, Kanav Sharma et al. (+4 more)

We investigate the evolution of electronic transport across the topological-trivial phase transition in ${\rm In}_{x}({\rm Bi}_{0.3}{\rm Sb}_{0.7})_{2-x}{\rm Te}_3$ thin films by systematically tuning the indium concentration $x$. Increasing $x$ reduces the effective spin-orbit coupling, driving a topological quantum phase transition near $x \approx 7\%$, and at higher disorder a crossover from diffusive to strongly localized transport around $x \approx 15\%$. In the diffusive regime, the magnetoconductance is well described by the Hikami-Larkin-Nagaoka formalism, with the evolution of the WAL prefactor $\alpha$ correlating with the band-inversion transition. Beyond the diffusive limit, transport crosses into variable-range hopping, accompanied by a striking reversal of magnetoconductance from negative to positive. The observed positive low-field magnetoconductance, its pronounced anisotropy, and its temperature evolution point to an orbital origin of the response. These features are naturally captured by incorporating the incoherent hopping mechanism of Raikh et al. together with wavefunction shrinkage, rather than by conventional quantum-correction frameworks. Our results provide a unified picture of how topology, spin-orbit coupling, and disorder collectively determine the full field-temperature magnetotransport landscape in this material class, establishing a clear experimental link between the topological phase transition and the onset of incoherent hopping-dominated conduction.
Read the full abstract

All authors Sambhu G Nath, Subhadip Manna, Kanav Sharma, Amar Verma, Ritam Banerjee, R K Gopal, Chiranjib Mitra

Materials Science

Topological charge and bulk-surface correspondence for quad-helicoid surface states in topological semimetals with two glide-time-reversal symmetries

Taiki Yukitake and Shuichi Murakami

Quad-helicoid surface states (QHSSs) are unique surface states with two pairs of helicoid surface states in topological semimetals such as Dirac semimetals. So far, topologically protected QHSSs are shown to appear in spinless systems with two $\mathcal{GT}$ symmetries and $\mathcal{T}$ symmetry ($\mathcal{G}$: glide, $\mathcal{T}$: time-reversal). In this paper, we show that topologically protected QHSSs also appear in spinful/spinless systems with only two $\mathcal{GT}$ symmetries by defining new topological charges and establishing the bulk-surface correspondence. We first define a local $Z_2\times Z_2$ monopole charge for gapless nodes at $\mathcal{GT}$-invariant high-symmetry points and a global $Z_2$ charge reflecting the global topological feature of $\mathcal{GT}$-symmetric topological semimetals. Next, we show that the latter $Z_2$ classification corresponds to the presence or absence of QHSSs on the surface with two $\mathcal{GT}$ symmetries. In addition, we provide simplified formulas of the $Z_2$ charge under additional symmetries, and clarify some symmetry conditions where QHSSs are filling-enforced.
Read the full abstract

Materials Science

Green and Sustainable Hydrogen-Anchored Solvent Enabling Stable Aqueous Zn Batteries

I. Al Kathemi, J. Caroni, T. Dehne et al. (+3 more)

Aqueous zinc (Zn) batteries provide many benefits, including high theoretical capacity, a low redox potential, and the abundance of Zn in Earth's crust. However, the benefits are often compromised by severe side reactions and dendrite growth, limiting their practical application. To mitigate these drawbacks, many studies have focused on high-concentration electrolytes to desolvate the Zn2+ solvation shell from water and to reduce the amount of free water. In this study, a methodology is proposed to achieve the benefits of highly concentrated electrolytes while using low salt concentrations. 5-methyl-2-pyrrolidone (5MP) was introduced as a safe and polar cosolvent capable of anchoring free water molecules through hydrogen bonding, enabled by its carbonyl and secondary amine groups. Additionally, by adding a co-salt containing a chaotropic ion, it is possible to disrupt the water network, enabling the development of high-performance aqueous Zn batteries. The synergy between anchoring water molecules and disrupting the overall water network proved to be an effective strategy for enhancing the overall Zn battery performance in a symmetric Zn cell, with lifetimes exceeding 2000 hours and 1400 hours at 1 C and 5 C, respectively. Analysis of the recovered Zn anode confirmed that the combination of 5MP and chaotropic ions enabled Zn deposition along the energetically favorable (002) plane, with no signs of surface dehydration observed by in situ Raman spectroscopy. Furthermore, long-term stability tests using a carbonyl-rich COF- and NaVO-based cathodes at various current densities further demonstrated the benefits of this approach. This work showcases the universality of a diluted electrolyte in combination with 5MP and chaotropic ions, bridging the gap between laboratory research and real-world applications.
Read the full abstract

All authors I. Al Kathemi, J. Caroni, T. Dehne, M. Souto, M. Antonietti, R. Bouchal

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

Buckling of knitted fabric wrapped around a rigid cylinder

Kotone Tajiri and Tomohiko G. Sano

Knitted fabrics exhibit high flexibility due to their periodic loop structures formed by bent yarns. Under compressive loading, they develop three-dimensional (3D) wrinkling patterns that reflect nonlinear interactions between yarn elasticity and local loop deformations, as observed when the sleeves of a sweater are rolled up. Despite their widespread use in garments and medical textiles, the relationship between loop-level geometry and macroscopic buckling remains less understood. Here, we investigate the 3D deformation of knitted fabrics wrapped around a rigid cylinder under uniaxial compression. Circumferential and axial stitch numbers are systematically varied to determine how loop geometry affects the evolution of wrinkle patterns. Samples with a small number of circumferential stitches exhibit sequential wrinkle formation from the compressed end, leading to an accordion-like wrinkle pattern, whereas those with a larger number of stitches form helical wrinkles simultaneously across the surface. Wrinkle morphology changes progressively with stitch geometry, accompanied by systematic variations in compressive force, loop deformation, and helical wrinkle angle. The development of helical wrinkles originates from subtle structural asymmetries introduced during manufacturing processes, including the tension applied during knitting and the direction of sample assembly. These results demonstrate that small variations in local loop deformation can lead to substantial differences in wrinkle morphology, highlighting the sensitivity of macroscopic buckling to microscopic structural features. The study establishes a direct link between loop-level mechanics and global deformation behavior, providing a basis for the predictive design of knitted structures with tailored mechanical responses and complex 3D patterns.
Read the full abstract

Materials Science

Surface-mediated reduction of ion-irradiation-induced damage in tungsten revealed by advanced ion channeling analysis

Xin Jin, Fredric Granberg, Kai Nordlund et al. (+3 more)

Tungsten is a leading candidate material for plasma-facing components in future fusion reactors. In this work, we integrate advanced ion channeling analysis with large-scale molecular dynamics simulations to uncover a pronounced surface-mediated reduction of radiation damage in single-crystal tungsten at elevated temperatures. We demonstrate how our unique analysis method can clearly resolve a dislocation-free zone near the surface and a transition region with suppressed defect density before reaching the bulk value. A possible explanation for the strong surface effect at elevated temperatures can be obtained by considering the coherent drift motion of dislocation loops toward the surface.
Read the full abstract

All authors Xin Jin, Fredric Granberg, Kai Nordlund, Sabina Markelj, Esther Punzón-Quijorna, Flyura Djurabekova

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

Canted ferromagnetic order in a distorted triangular-lattice magnet Na$_2$SrCo(VO$_4$)$_2$

Tengfei Peng, Xiaobai Ma, Xinyang Liu et al. (+5 more)

Triangular-lattice cobaltates with glaserite-type $X_2Y$Co($T$O$_4)_2$ structure provide an ideal platform to investigate intriguing quantum magnetism. Here we report a comprehensive study of the structural and magnetic properties of a triangular-lattice cobalt vanadate $\rm Na_2SrCo(VO_4)_2$. Room-temperature x-ray and neutron powder diffraction confirm that $\rm Na_2SrCo(VO_4)_2$ crystallizes in the monoclinic $P2_1/c$ space group with slightly distorted triangular layers of $\rm Co^{2+}$ ions. Magnetization measurements reveal a ferromagnetic transition at $T\rm_C \approx 3.4~{\rm K}$, where a sharp $\lambda$-type anomaly is observed in the specific heat. The magnetic entropy recovered up to 55 K approaches 90$\%$ of $R{\rm ln}2$, supporting an effective spin-1/2 state of Co$^{2+}$ ions at low temperature. Neutron diffraction at 2.3 K (below $T_{\rm C}$) further confirms a long-range canted ferromagnetic order with the Co$^{2+}$ moments aligned in the $ac$ plane and the ordered moment size of $\sim$ 2.6 $\mu\rm_{B}$. Comparing with its sister compounds with a trigonal symmetry, $\rm Na_2BaCo(VO_4)_2$ with a collinear ferromagnetic structure and the recently discovered spin supersolid candidate $\rm Na_2BaCo(PO_4)_2$ with a distinct Y-like antiferromagnetic ground state, this study indicates the decisive role of the $T{\rm O_4}$ tetrahedra in tuning exchange interactions and contrasting magnetic behaviors of these glaserite-structure compounds.
Read the full abstract

All authors Tengfei Peng, Xiaobai Ma, Xinyang Liu, Feiran Shen, Lunhua He, Junsen Xiang, Wenyun Yang, Wentao Jin

Materials Science

X-ray detected ferromagnetic resonance spectrometer with an out-of-vacuum photodetector

Tetsuro Ueno, Yasuo Takeichi, Masaki Mizuguchi et al. (+10 more)

X-ray detected ferromagnetic resonance (XFMR) spectroscopy is an experimental technique for element-specific spin dynamics in the GHz regime and has been utilized to study spintronic materials. The XFMR signal is usually obtained by detecting X-ray excited optical luminescence (XEOL) emitted from a sample substrate. Here, we report the development of an XFMR spectrometer that is designed to place a photodetector for XEOL detection outside an ultra-high-vacuum chamber. This configuration allows for the easy replacement of detectors, such as photodiodes, CCD cameras, and spectrometers, depending on the experimental requirements. We demonstrated the measurement of XEOL spectra from MgO using a visible light spectrometer as well as the detection of XFMR signals originating from the spin precession of a permalloy (Ni80Fe20) thin film using a photodiode detector. The XFMR spectrometer with an out-of-vacuum photodetector expands possibilities for advanced measurements such as XFMR microscopy.
Read the full abstract

All authors Tetsuro Ueno, Yasuo Takeichi, Masaki Mizuguchi, Hideaki Iwasawa, Yoshiyuki Ohtsubo, Kanta Ono, Hiroyuki Okazaki, Songtian Li, Seiji Sakai, Tetsuya Yamaki, Tetsu Watanuki, Yoshinori Katayama, Chiharu Mitsumata

Materials Science

Site-selective enhancement of Eu emission in delta-doped GaN

Amelia R. Klein, Hayley J. Austin, Fumikazu Murakami et al. (+7 more)

Europium-doped gallium nitride (GaN:Eu) is a promising platform for classical and quantum optoelectronic applications. When grown using organometallic vapor-phase epitaxy, the dominant red emission from Eu exhibits an inhomogeneous photoluminescence (PL) spectrum due to contributions from several non-equivalent incorporation sites that can be distinguished with combined excitation emission spectroscopy. Energy transfer from the GaN bandgap to the majority site is inefficient, limiting the performance of GaN:Eu LEDs and resulting in an inhomogeneous emission spectrum dominated by disproportionate contributions from minority sites. In this work, we use site-selective spectroscopy to characterize the photoluminescence properties of delta-doped structures with alternating doped and undoped layers of varying thicknesses and demonstrate that they selectively enhance emission from the majority site when compared to uniformly-doped samples. Samples with 2-nm and 10-nm doped layers show much greater PL intensity per Eu concentration as well as more efficient energy transfer to the majority site, which are both highly desirable for creating power-efficient LEDs. Meanwhile, a sample with 1-nm doped layers shows emission only from the majority site, resulting in a narrow, homogeneous emission spectrum that is desirable for quantum technologies. This utilization of delta-doping has the potential to be broadly applicable for engineering desirable defect properties in rare-earth doped semiconductors.
Read the full abstract

All authors Amelia R. Klein, Hayley J. Austin, Fumikazu Murakami, Jamie Ford, Jun Tatebayashi, Masayoshi Tonouchi, Yasufumi Fujiwara, Volkmar Dierolf, Lee C. Bassett, Brandon Mitchell

Materials Science

Dependence of Radiation Induced Segregation of Cr on Sink Dimensionality and Morphology in Fe-Cr Alloys

Mohammadhossein Nahavandian, Anter El-Azab and Enrique Martinez

Radiation-induced segregation (RIS) and chemical redistribution in structural alloys can significantly degrade material performance, ultimately leading to failure. In this study, building on previous work by the authors [1], we investigate how the dimensional characteristics of sinks influence solute concentration distributions and segregation behavior. Specifically, we utilize a kinetic Monte Carlo (KMC) model to simulate atomic-scale diffusion and analyze segregation processes in an Fe-3Cr alloy. Our analysis includes three representative sink geometries: one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) planar sinks to capture the effects of sink dimensionality on Cr segregation at grain boundaries (GBs). We also found solutions of concentration and segregation profiles in these cases as well as for a 3D spherical sink. KMC simulations are performed over a range of temperatures to assess thermal effects on Cr redistribution. The results reveal distinct segregation profiles and concentration gradients, although the dependence with sink density seems to remain linear in all cases with planar sinks. The analytical results show that this is not the case in spherical domains, with a more complex dependence of segregation on sink density. Our finite difference solutions for domains including 2D and 3D planer sinks show agreement with corresponding KMC results.
Read the full abstract

Materials Science

Efficient Nudged Elastic Band Method using Neural Network Bayesian Algorithm Execution

Pranav Kakhandiki, Sathya Chitturi, Daniel Ratner et al. (+1 more)

The discovery of a minimum energy pathway (MEP) between metastable states is crucial for scientific tasks including catalyst and biomolecular design. However, the standard nudged elastic band (NEB) algorithm requires hundreds to tens of thousands of compute-intensive simulations, making applications to complex systems prohibitively expensive. We introduce Neural Network Bayesian Algorithm Execution (NN-BAX), a framework that jointly learns the energy landscape and the MEP. NN-BAX sequentially fine-tunes a foundation model by actively selecting samples targeted at improving the MEP. Tested on Lennard-Jones and Embedded Atom Method systems, our approach achieves a one to two order of magnitude reduction in energy and force evaluations with negligible loss in MEP accuracy and demonstrates scalability to >100-dimensional systems. This work is therefore a promising step towards removing the computational barrier for MEP discovery in scientifically relevant systems, suggesting that weeks-long calculations may be achieved in hours or days with minimal loss in accuracy.
Read the full abstract

All authors Pranav Kakhandiki, Sathya Chitturi, Daniel Ratner, Sean Gasiorowski

Tuesday 16 December

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

Composition-agnostic prediction of self-assembly in multicomponent amphiphile mixtures from molecular structure

Yuuki Ishiwatari, Takahiro Yokoyama, Tomoya Kojima et al. (+2 more)

Predicting self-assembly in multi-component amphiphilic systems is challenging due to the complexity of intercomponent interactions and the combinatorial growth of possible formulations. In this study, we develop a unified machine-learning framework that directly predicts self-assembly behavior from the molecular structures of constituent components, independent of the number or identity of those components. We extend the critical packing parameter (CPP) to multi-component systems and generate a large dataset of self-assembled morphologies using dissipative particle dynamics (DPD) simulations. By systematically evaluating twelve combinations of feature extraction methods and model architectures, we find that models incorporating a fully connected graph convolutional network (GCN) layer achieve superior performance, with the GCN-GCN architecture accurately capturing both intramolecular relationships and intercomponent interactions. Notably, this model exhibits strong extrapolative capability: it accurately predicts CPP values for five-component mixtures even when trained only on systems with fewer components, and it maintains high accuracy for mixtures composed of molecular species that are entirely absent from the training data. These results demonstrate that a composition-agnostic predictive framework can enable efficient virtual screening and provide a foundation for the rational design of complex amphiphilic materials.
Read the full abstract

All authors Yuuki Ishiwatari, Takahiro Yokoyama, Tomoya Kojima, Taisuke Banno, Noriyoshi Arai

Materials Science

A High-Flux and High-Efficiency Setup for Magneto-Infrared Spectroscopy

Zeping Shi, Wenbin Wu, Zhiwei Zhang et al. (+14 more)

We report the design and implementation of a high-flux, high-efficiency magneto-infrared spectroscopy system optimized for broadband measurements in high magnetic fields. The setup integrates a Fourier transform infrared spectrometer, a 12 T cryogen-free superconducting magnet, precision-polished and gold-plated light tubes, custom-designed reflective focusing modules for Faraday and Voigt geometries, and an external multi-detector chamber with motorized selection. Optical throughput is maximized by reducing light tube loss from 65.5%/m to 22.0%/m via abrasive flow and mechanical polishing followed by gold electroplating, and by adopting a single-on-axis parabolic-mirror Faraday module that increases the effective numerical aperture from 0.14 to 0.36, enhancing collection efficiency by nearly an order of magnitude. An eight-position motorized sample stage and fully automated control over magnetic field, temperature, optical path, and detector choice enable high-throughput measurements without repeated warm-ups. The optimized configuration achieves a root-mean-square noise level of 0.0061% in a 2-minute integration for a 40% reflectivity sample, corresponding to a signal-to-noise ratio exceeding 16000. System capabilities are demonstrated by resolving weak replica bands in EuCd2As2 and faint Landau level transitions in LaAlSi.
Read the full abstract

All authors Zeping Shi, Wenbin Wu, Zhiwei Zhang, Yuhan Du, Chenyao Xu, Guangyi Wang, Mingsen Zhou, Congming Hao, Xianghao Meng, Xiangyu Jiang, Chunhui Pan, Wei Lu, Hao Shen, Haifeng Pan, Zhenrong Sun, Junhao Chu, Xiang Yuan

Materials Science · Cross-listed from quant-ph

Roadmap: 2D Materials for Quantum Technologies

Qimin Yan, Tongcang Li, Xingyu Gao et al. (+29 more)

Two-dimensional (2D) materials have emerged as a versatile and powerful platform for quantum technologies, offering atomic-scale control, strong quantum confinement, and seamless integration into heterogeneous device architectures. Their reduced dimensionality enables unique quantum phenomena, including optically addressable spin defects, tunable single-photon emitters, low-dimensional magnetism, gate-controlled superconductivity, and correlated states in Moiré superlattices. This Roadmap provides a comprehensive overview of recent progress and future directions in exploiting 2D materials for quantum sensing, computation, communication, and simulation. We survey advances spanning spin defects and quantum sensing, quantum emitters and nonlinear photonics, computational theory and data-driven discovery of quantum defects, spintronic and magnonic devices, cavity-engineered quantum materials, superconducting and hybrid quantum circuits, quantum dots, Moiré quantum simulators, and quantum communication platforms. Across these themes, we identify common challenges in defect control, coherence preservation, interfacial engineering, and scalable integration, alongside emerging opportunities driven by machine$-$learning$-$assisted design and integrated experiment$-$theory feedback loops. By connecting microscopic quantum states to mesoscopic excitations and macroscopic device architectures, this Roadmap outlines a materials-centric framework for integrating coherent quantum functionalities and positions 2D materials as foundational building blocks for next-generation quantum technologies.
Read the full abstract

All authors Qimin Yan, Tongcang Li, Xingyu Gao, Sumukh Vaidya, Saakshi Dikshit, Yue Luo, Stefan Strauf, Reda Moukaouine, Anton Pershin, Adam Gali, Zhenyao Fang, Harvey Stanfield, Ivan J. Vera-Marun, Michael Newburger, Simranjeet Singh, Tiancong Zhu, Mauro Brotons-Gisbert, Klaus D. Jöns, Brian D. Gerardot, Brian S. Y. Kim, John R. Schaibley, Kyle L. Seyler, Jesse Balgley, James Hone, Kin Chung Fong, Lin Wang, Guido Burkard, Yihang Zeng, Tobias Heindel, Serkan Ateş, Tobias Vogl, Igor Aharonovich

Materials Science

Quadrene: A Novel Quasi-2D Carbon Allotrope with High Carrier Mobility

Kleuton A. L. Lima, José A. dos S. Laranjeira, Neymar J. N. Cavalcante et al. (+4 more)

We present a comprehensive first-principles investigation of a novel carbon allotrope characterized by quasi-tetragonal atomic motifs and quasi-two-dimensional structural behavior. Structural analysis reveals an open framework composed of alternating diamond-like and square units, while thermodynamic assessments indicate a negative formation energy, suggesting high intrinsic stability. Phonon spectra confirm dynamical robustness, and ab initio molecular dynamics simulations at 1000~K validate its thermal resilience. Furthermore, the system exhibits an indirect bandgap of 1.58 eV at the HSE06 level, anisotropic mechanical behavior, and a broadband optical response, reinforcing its potential for nanoelectronic and optoelectronic applications. The highly anisotropic mechanical behavior is characterized by an in-plane Young's modulus ranging from 80 to 550 GPa, depending on crystallographic direction. Additionally, the electronic transport properties exhibit pronounced anisotropy, with hole mobilities reaching up to 5.83 x 10^6 cm^2/V . s and electron mobilities up to 6.40 x 10^6 cm^2/V . s along different crystallographic directions, highlighting the material's potential for directionally selective nanoelectronic device applications.
Read the full abstract

All authors Kleuton A. L. Lima, José A. dos S. Laranjeira, Neymar J. N. Cavalcante, Nicolas F. Martins, Julio R. Sambrano, Douglas S. Galvão, Luiz A. Ribeiro Jr

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

Applicability of the cumulant expansion method for the calculation of transport properties in electron-phonon systems

Petar Mitrić, Veljko Janković, Darko Tanasković et al. (+1 more)

We assess the accuracy of the cumulant expansion (CE) method, combined with the independent-particle approximation (IPA), for calculating charge mobility in electron-phonon systems. As representative testbeds, we consider the Peierls and Fröhlich models, which serve as simplified frameworks where accurate or numerically exact benchmarks are available. These are used to compare the CE results with those obtained using the Boltzmann formalism, the Migdal approximation, and its self consistent extension-approaches that are presently the most commonly employed alternatives for transport calculations. Supported by analytical arguments based on spectral sum rules and by our previous results for the Holstein model, we argue that, for weak to moderate coupling strengths and not-too-low temperatures, the CE within the IPA framework yields accurate results. In the case of the Peierls model, the role of vertex corrections is also discussed.
Read the full abstract

All authors Petar Mitrić, Veljko Janković, Darko Tanasković, Nenad Vukmirović

Materials Science

Kagome Topology in Two-Dimensional Noble-Metal Monolayers

Carlos M. O. Bastos, Emanuel J. A. dos Santos, José A. dos S. Laranjeira et al. (+4 more)

Two-dimensional (2D) metallic lattices with kagome topology provide a unique platform for exploring the interplay between geometric frustration, reduced coordination, and lattice stability in elemental systems. Motivated by the recent experimental realization of atomically thin gold layers and kagome goldene, we present a first-principles investigation of free-standing kagome monolayers of Cu, Ag, and Au. Using density functional theory combined with lattice dynamics and ab initio molecular dynamics, we systematically assess their structural, mechanical, dynamical, and thermal stability. All kagome monolayers satisfy the 2D Born criteria and exhibit relatively low in-plane stiffness compared to graphene and hexagonal goldene, reflecting the porous nature of the kagome lattice and its metallic bonding. Among the three systems, the Au-based lattice displays the highest in-plane Young's modulus. Phonon calculations reveal that the unstrained kagome phase is dynamically unstable for all metals. However, a moderate biaxial tensile strain of 5% stabilizes the Ag and Au monolayers, while Cu retains residual unstable modes. Finite-temperature simulations further show that Cu rapidly reconstructs toward a trigonal lattice, Ag remains metastable at low temperature but collapses at room temperature, and Au exhibits competing kagome and trigonal motifs at 300 K, indicating near-degeneracy between these phases. These results establish that strain engineering and atomic size are key determinants of the stability of metallic kagome monolayers and provide guidance for future substrate-supported realizations.
Read the full abstract

All authors Carlos M. O. Bastos, Emanuel J. A. dos Santos, José A. dos S. Laranjeira, Kleuton A. L. Lima, Alexandre C. Dias, Douglas S. Galvão, Luiz A. Ribeiro Jr

Materials Science

A computational study of thermoelectric conversion in the PbSe$_{x}$Te$_{1-x}$ semiconductor alloys

M. Kaid Slimane, B. N. Brahmi, M. Bouchenaki et al. (+1 more)

The present theoretical study focuses on the structural, electronic and thermoelectric properties of PbTe, PbSe and their ternary alloys PbSe$_{x}$Te$_{1-x}$, using the density functional theory (DFT) by the full potential linearised augmented plane wave (FP-LAPW) method implemented in Wien2k code. Structural properties were performed by using the generalized gradient approximation of Perdew Burke and Ernzenhof (GGA-PBE) scheme. The results show that the calculated lattice parameters are in good agreement with theoretical data previously obtained. For electronic properties, we noticed that for all the compounds of PbSe$_{x}$Te$_{1-x}$, we have a direct band gap in L point. For thermoelectric properties, we used BoltzTraP2 code and Gibbs2 code. Our results show that the PbSe$_{x}$Te$_{1-x}$ compounds have reached a value of 2.55 for the figure of merit, which indicates that our material is a good thermoelectric candidate.
Read the full abstract

All authors M. Kaid Slimane, B. N. Brahmi, M. Bouchenaki, S. Bekhechi

Materials Science

Investigation of density of states and charge carrier mobility in amorphous semiconductors via time-of-flight photocurrent analysis

F. Serdouk, A. Boumali, M. L. Benkhedir et al. (+1 more)

The present study examines the electronic transport characteristics of amorphous semiconductors through TOF measurements and numerical simulations. The primary objective is to determine the DOS in amorphous selenium (a-Se) and to assess the temperature and electric field dependence of the hole mobility. A comprehensive investigation of localized states within the mobility gap is performed using Laplace transform analysis of ToF photocurrent transients, combined with the multiple trapping model. This approach enables accurate reconstruction of the DOS across a wide temperature range, allowing clear identification of shallow and deep trap levels and revealing thermally activated transport mechanisms. Simulated ToF currents are also used to evaluate the hole drift mobility under various thermal and field conditions. Activation energies are extracted from Arrhenius plots of the mobility data. The results support a physically consistent description of the electronic structure in a-Se and validate the applicability of Laplace-based techniques for probing charge transport in disordered semiconductors.
Read the full abstract

All authors F. Serdouk, A. Boumali, M. L. Benkhedir, Y. Goutal