Materials Science · Cross-listed from cond-mat.supr-con
Chimeric states of matter: Meissner effect without superconductivity
Michael J Landry and Mingda Li
Symmetry is central to how we classify phases of matter: solids break spatial translations, superfluids break particle-number conservation, and
superconductors "break" gauge
symmetry. Mixed anomalies involving higher-form
symmetries, however, present a generalization of spontaneous
symmetry breaking that admits a wider and more versatile set of possibilities. We introduce chimeric states of matter, in which aspects of broken and unbroken phases coexist. We find that the Meissner effect – usually regarded as the defining hallmark of superconductivity – can occur in media that are resistive or even insulating when probed by electric fields. We demonstrate this by constructing an effective field theory of "
symmetry chimerization" and propose that Josephson junction networks could provide a laboratory realization. These results broaden the landscape of possible phases of matter, showing that physical media can mix features of
symmetry-restored and
symmetry-broken states in a single substrate.
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Materials Science · Cross-listed from physics.class-ph
Mechanically concealed holes
Kanka Ghosh and Andreas M. Menzel
When a hole is introduced into an elastic material, it will usually act to reduce the overall mechanical stiffness. A general ambition is to investigate whether a stiff shell around the hole can act to maintain the overall mechanical properties. We consider this effect from a macroscopic continuum perspective down to atomistic scales. For this purpose, we focus on the basic continuum example situation of an isotropic, homogeneous, linearly elastic material loaded uniformly under compressive plane strain for low concentrations of holes. As we demonstrate, the thickness of the shell can be adjusted in a way to maintain the overall stiffness of the system. We derive a corresponding mathematical expression for the thickness of the shell that conceals the hole. Thus, one can work with given materials to mask the presence of the holes simply by adjusting the thickness of the surrounding shells, with no need to change the materials. Our predictions from linear elasticity continuum theory are extended to atomistic levels using molecular dynamics simulations of a model Lennard-Jones solid. These extensions attest the robustness of our predictions down to atomistic scales. Thus, they open a straightforward possibility to adjust the strategy of mechanical cloaking via atomistic manipulations. From both perspectives, the underlying concept is important in the context of light-weight construction.
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Materials Science · Cross-listed from cs.CV
Deep learning denoising unlocks quantitative insights in operando materials microscopy
Samuel Degnan-Morgenstern, Alexander E. Cohen, Rajeev Gopal et al. (+4 more)
Operando microscopy provides direct insight into the dynamic chemical and physical processes that govern functional materials, yet measurement noise limits the effective resolution and undermines quantitative analysis. Here, we present a general framework for integrating unsupervised deep learning-based denoising into quantitative microscopy workflows across modalities and length scales. Using simulated data, we demonstrate that deep denoising preserves physical fidelity, introduces minimal bias, and reduces uncertainty in model learning with partial differential equation (PDE)-constrained optimization. Applied to experiments, denoising reveals nanoscale chemical and structural heterogeneity in scanning transmission X-ray microscopy (STXM) of lithium iron phosphate (LFP), enables automated particle
segmentation and phase classification in optical microscopy of graphite electrodes, and reduces noise-induced variability by nearly 80% in
neutron radiography to resolve heterogeneous lithium transport. Collectively, these results establish deep denoising as a powerful, modality-agnostic enhancement that advances quantitative operando imaging and extends the reach of previously noise-limited techniques.
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All authors Samuel Degnan-Morgenstern, Alexander E. Cohen, Rajeev Gopal, Megan Gober, George J. Nelson, Peng Bai, Martin Z. Bazant
Materials Science
Evolution of Magnetoresistance in the magnetic topological semimetals NdSbxTe2-x
Santosh Karki Chhetri, Rabindra Basnet, Krishna Pandey et al. (+6 more)
Magnetic topological semimetals LnSbTe (Ln = lanthanide elements) provide a platform to study the interplay of structure, magnetism,
topology, and electron correlations. Varying Sb and Te compositions in LnSbxTe2-x can effectively control the electronic,
magnetic, and transport properties. Here, we report the
evolution of transport properties with Sb and Te contents in NdSbxTe2-x, (0 < x < 1). Our work reveals nonmonotonic
evolution in magnetoresistance with varying composition stoichiometry. Specifically, reducing Sb content x leads to strong negative magnetoresistance up to 99.9%. Such a strong magnetoresistance, which is likely attributed to the interplay between structure, magnetism, and electronic bands, establishes this material as a promising platform for investigating topological semimetal for future device applications.
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All authors Santosh Karki Chhetri, Rabindra Basnet, Krishna Pandey, Gokul Acharya, Sumaya Rahman, Md Rafique Un Nabi, Dinesh Upreti, Hugh O.H. Churchill, Jin Hu
Materials Science · Cross-listed from cond-mat.soft
Poroelasticity in the presence of active fluids
Riccardo Cavuoto, Stefania Scala, Arsenio Cutolo et al. (+2 more)
This work presents a model for characterizing porous, deformable media embedded with magnetorheological fluids (MRFs). These active fluids exhibit tunable mechanical and rheological properties that can be controlled through the application of a
magnetic field, which induces a phase transition from a
liquid to a solid-like state. This transition profoundly affects both stress transmission and fluid flow within the composite, leading to a behaviour governed by a well-defined threshold that depends on the ratio between the pore size and the characteristic size of clusters of
magnetic particles, and can be triggered by adjusting the
magnetic field intensity. These effects were confirmed through an experimental campaign conducted on a prototype composite obtained by imbibing a selected MRF into commercial sponges. To design and optimize this new class of materials, a linear poroelastic formulation is proposed and validated through comparison with experimental results. The constitutive relationships, i.e. overall elastic constitutive tensor and permeability, of the model are updated from phenomenological observations, exploiting the experimental data obtained for both the pure fluid and the composite material. The findings demonstrate that the proposed simplified formulation is sufficiently robust to predict and optimize the behaviour of porous media containing MRFs. Such materials hold significant promise for a wide range of engineering applications, including adaptive exosuits for human tissue and joint rehabilitation, as well as innovative structural systems.
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All authors Riccardo Cavuoto, Stefania Scala, Arsenio Cutolo, Giuseppe Mensitieri, Massimiliano Fraldi
Materials Science · Cross-listed from cond-mat.supr-con
Reducing the strain required for ambient-pressure superconductivity in bilayer nickelates
Yaoju Tarn, Yidi Liu, Florian Theuss et al. (+7 more)
The remarkable discovery of high temperature superconductivity in bulk
bilayer nickelates under high pressure has prompted the
conjecture that epitaxial compressive strain might mimic essential aspects of hydrostatic pressure. The successful realization of superconductivity in films on SrLaAlO4 (001) (SLAO) supports this correspondence, yet it remains unclear whether the rich pressure-temperature phase diagram of
bilayer nickelates can be systematically mapped (and studied at ambient pressure) as a function of epitaxial strain. To this end, experimental access near the elusive edge of the superconducting phase boundary would provide invaluable insight into the nature of the superconducting state and the ground state from which it emerges. It would also offer a
benchmark for theoretical models. Here we report superconducting
bilayer nickelates grown on LaAlO3 (001) (LAO), where the compressive strain required for ambient-pressure superconductivity is nearly halved to -1.2%. These films exhibit a superconducting onset above 10 K and reach zero resistance at 3 K, with normal-state transport properties differing from those of films grown on SLAO. Our results offer a new opportunity to probe emergent phenomena near the superconducting phase boundary in the strain-temperature phase diagram of
bilayer nickelates.
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All authors Yaoju Tarn, Yidi Liu, Florian Theuss, Jiarui Li, Bai Yang Wang, Jiayue Wang, Vivek Thampy, Zhi-Xun Shen, Yijun Yu, Harold Y. Hwang
Materials Science
Kinematical and dynamical contrast of dislocations in thick GaN substrates observed by synchrotron-radiation X-ray topography under six-beam diffraction conditions
Yongzhao Yao, Yoshiyuki Tsusaka and Yukari Ishikawa
Dislocations in a thick ammonothermal GaN substrate were investigated using synchrotron-radiation X-ray topography (SR-XRT) under six-beam diffraction conditions. The high brilliance of the synchrotron source enabled the observation of the super-Borrmann effect, which markedly enhanced the anomalous transmission of X-rays through the 350~$\mu$m-thick
crystal. Systematic variation of the deviation angle~$\Delta\omega$ revealed a clear transition from kinematical to dynamical diffraction, consistent with theoretical predictions based on dynamical diffraction theory. By selectively exciting five equivalent two-beam diffraction conditions near the six-beam configuration, the Burgers vectors of individual threading edge dislocations (TEDs) were determined according to the $g\cdot b$ invisibility criterion. The measured dislocation image widths agreed well with calculated values derived from the extinction distance and $|g\cdot b|$ dependence, confirming that most dislocations possess Burgers vectors containing an $a$-type component of $\frac{1}{3}\langle 11\bar{2}0\rangle$ or $\frac{2}{3}\langle 11\bar{2}0\rangle$. These results demonstrate that SR-XRT under multibeam diffraction provides a powerful, nondestructive method for quantitative dislocation analysis in thick GaN
crystals, offering valuable insights into defect structures critical for high-performance GaN-based electronic devices.
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Materials Science
First-Principles Study of Transition Metal Doped in 2D Polyaramid for Novel Material Modelling
Ravi Trivedi, Chaithanya Purushottam Bhat, Shakti S. Ray et al. (+1 more)
We present a first–principles density functional theory (DFT) study of transition metal (TM = Ti, Cr, Mn, Fe, Co, Ni) functionalized two–dimensional polyaramid (2DPA) to explore their structural, electronic, and
magnetic properties. Mechanical parameters, such as bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and Pugh ratio, together with
phonon dispersion, confirm the mechanical and dynamic stability of all doped systems. Electronic structure analysis shows strong binding of Co, Cr, Fe, Ni, and Ti with formation energies between –1.15 eV and –2.96 eV, while Mn binds more weakly (–0.67 eV). TM doping introduces new electronic states that reduce the band gap, with Fe-doped 2DPA exhibiting the lowest value of 0.26 eV. The systems display predominantly
ferromagnetic ordering, with
magnetic moments of 1.14 {\mu}B (Co), 3.57 {\mu}B (Cr), 2.26 {\mu}B (Fe), 4.19 {\mu}B (Mn), and 1.62 {\mu}B (Ti). These results demonstrate that TM–doped 2DPA possesses tunable
magnetic and electronic characteristics, highlighting its potential for spintronic applications.
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All authors Ravi Trivedi, Chaithanya Purushottam Bhat, Shakti S. Ray, Debashis Bandyopadhyay
Materials Science
Learning viscoplastic constitutive behavior from experiments: II. Dynamic indentation
Andrew Akerson, Aakila Rajan, Daniel Casem et al. (+1 more)
We continue the development of a method to accurately and efficiently identify the constitutive behavior of complex materials through full-field observations that we started in Akerson, Rajan and Bhattacharya (2024). We formulate the problem of inferring constitutive relations from experiments as an indirect inverse problem that is constrained by the balance laws. Specifically, we seek to find a constitutive behavior that minimizes the difference between the experimental observation and the corresponding quantities computed with the model, while enforcing the balance laws. We formulate the forward problem as a boundary value problem corresponding to the experiment, and compute the sensitivity of the objective with respect to the model using the adjoint method. In this paper, we extend the approach to include contact and study dynamic indentation. Contact is a nonholonomic constraint, and we introduce a Lagrange multiplier and a slack variable to address it. We demonstrate the method on synthetic data before applying it to experimental observations on rolled homogeneous armor steel and a polycrystalline aluminum
alloy.
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All authors Andrew Akerson, Aakila Rajan, Daniel Casem, Kaushik Bhattacharya
Materials Science
Synthesis of organic-inorganic perovskite and all-inorganic lead-free double perovskite nanocrystals by femtosecond laser pulses
Volodymyr Vasylkovskyi, Andrey Evlyukhin, Elena Schlein et al. (+5 more)
Perovskite materials are at the forefront of modern materials science due to their exceptional structural, electronic, and optical properties. The controlled fabrication of perovskite nanostructures is crucial for enhancing their performance, stability, and scalability, directly impacting their applications in next-generation devices such as
solar cells, LEDs, and sensors. Here, we present a novel, ligand-free approach to synthesize perovskite nanocrystals (NCs) with average sizes up to 100 nm, using femtosecond pulsed
laser ablation (PLA) in ambient air without additional
liquid media. We demonstrate this method for both organic-inorganic (methylamino lead) hybrid perovskites (MAPbX3, X = Cl, Br, I) and fully inorganic lead-free double perovskites (Cs2AgBiX6, X = Cl, Br), achieving high-purity NCs without stabilizing ligands - a critical advancement over conventional chemical synthesis methods. By tailoring
laser parameters, we systematically elucidate the influence of perovskite composition (halide type, organic vs. inorganic cation, single versus double perovskite structure) on the ablation process and the resulting nanocrystal properties. Transmission electron microscopy and X-ray diffraction confirm the preservation of crystallinity, with MAPbX3 forming larger (approximately 90 nm) cubic NCs and Cs2AgBiX6 forming smaller (approximately 10 nm) rounded NCs. Photoluminescence spectroscopy reveals pronounced size-dependent blue shifts (17-40 nm) due to
quantum confinement, particularly for Br and I containing perovskites. This clean, scalable, and versatile PLA approach not only provides direct access to high-purity, ligand-free perovskite NCs with tunable optical properties but also represents a significant advance in the fabrication of nanostructures, enabling the exploration of new perovskite-based optoelectronic and
quantum devices.
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All authors Volodymyr Vasylkovskyi, Andrey Evlyukhin, Elena Schlein, Mykola Slipchenko, Roman Kiyan, Kestutis Kurselis, Vladimir Dyakonov, Boris Chichkov
Materials Science
Molecular ink-based synthesis of Bi(SzSe1-z)(IxBr1-x) solid solutions as tuneable materials for sustainable energy applications
David Rovira, Ivan Caño, Cibran Lopez et al. (+16 more)
Quasi-one-dimensional (Q-1D) van der Waals chalcohalides have emerged as promising materials for advanced energy applications, combining tunable optoelectronic properties and composed by earth-abundant and non-toxic elements. However, their widespread application remains hindered by challenges such as anisotropic
crystal growth, composition control and lack of knowledge on optoelectronic properties. A deeper understanding of the intrinsic limitations of these materials, as well as viable defect mitigation strategies like the engineering of solid solutions, is critical. This work presents a low-temperature synthesis route based on molecular ink deposition enabling direct crystallization of tunable Bi(SzSe1-z)(IxBr1-x) solid solutions without need for binary chalcogenide precursors. This approach yields phase-pure films with precise control over morphology, composition, and crystallographic orientation. XRD analysis and DFT calculations confirm the formation of homogeneous solid solutions, while optoelectronic measurements reveal the distinct roles of halogen and chalcogen anions in tuning bandgap energy and carrier type, with Se shifting downwards the conduction band. The versatility of this synthesis technique enables morphology control ranging from compact films to rod-shaped microcrystals, expanding the functional adaptability of these materials. These findings offer a foundational framework for defect engineering and the scalable integration of chalcohalides in next-generation energy technologies, including photovoltaics, photocatalysis, thermoelectrics, and chemical sensing.
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All authors David Rovira, Ivan Caño, Cibran Lopez, Alejandro Navarro-Güell, José Miguel Asensi, Lorenzo Calvo-Barrio, Laura Garcia-Carreras, Xavier Alcobe, Luis Cerqueira, Victoria Corregidor, Yudania Sanchez, Sonia Lanzalaco, Alex Jimenez-Arquijo, Outman El Khouja, Jonathan W. Turnley, Rakesh Agrawal, Claudio Cazorla, Joaquim Puigdollers, Edgardo Saucedo
Materials Science
First-principles calculations of thermal transport at metal/silicon interfaces: evidence of interfacial electron-phonon coupling
Michaël De San Féliciano, Christophe Adessi, Julien El Hajj et al. (+4 more)
With the increasing miniaturization of electronic components and the need to optimize thermal management, it has become essential to understand heat transport at metal/
semiconductor interfaces. While it has been recognized decades ago that an electron
phonon channel may take place at metal-
semiconductor interfaces, its existence is still controversial. Here, we investigate thermal transport at metal-silicon interfaces using the combination of first principles calculations and nonequilibrium Green's function (NEGF). We explain how to correct NEGF formalism to account for the out of
equilibrium nature of the energy carriers in the vicinity of the interface. The relative corrections to the
equilibrium distribution are shown to arise from the spectral mean free paths of silicon and may reach 15 percents. Applying these corrections, we compare the predictions of NEGF to available experimental data for Au/Si, Pt/Si and Al/Si interfaces. Based on this comparison, we infer the value of the electron
phonon interfacial thermal conductance by employing the two temperature model. We find that interfacial thermal transport at Au/Si interfaces is mainly driven by
phonon phonon processes, and that electron
phonon processes play a negligible role in this case. By contrast, for Al/Si interfaces, we show that
phonon-
phonon scattering alone can not explain the experimental values reported so far, and we estimate that the electron-
phonon interfacial conductance accounts for one third of the total conductance. This work demonstrates the importance of the electron-
phonon conductance at metal-silicon interfaces and calls for systematic experimental investigation of thermal transport at these interfaces at low temperatures. It paves the way for an accurate model to predict the conductance associated to the interfacial electron
phonon channel.
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All authors Michaël De San Féliciano, Christophe Adessi, Julien El Hajj, Nicolas Horny, François Detcheverry, Manuel Cobian, Samy Merabia
Materials Science · Cross-listed from physics.optics
Unveiling Spin Transition at Single Particle Level in Levitating Spin Crossover Nanoparticles
Elena Pinilla-Cienfuegos, Lucas Mascaró-Burguera, Ramón Torres-Cavanillas et al. (+4 more)
The ability to control and understand the phase transitions of individual nanoscale building blocks is key to advancing the next generation of low-power reconfigurable nanophotonic devices. To address this critical challenge, molecular nanoparticles (NPs) exhibiting a
spin crossover (SCO) phenomenon are trapped by coupling a quadrupole Paul trap with a multi-spectral polarization-resolved scattering microscope. This contact-free platform simultaneously confines, optically excites, and monitors the
spin transition in Fe(II)-triazole NPs in a pressure-tunable environment, eliminating substrate artifacts. Thus, we show light-driven manipulation of the
spin transition in levitating NPs free from substrate-induced effects. Using the robust
spin bistability near room temperature of our SCO system, we quantify reversible opto-volumetric changes of up to 6%, revealing precise switching thresholds at the single-particle level. Independent pressure modulation produces a comparable size increase, confirming mechanical control over the same bistable transition. These results constitute full real-time control and readout of
spin states in levitating SCO NPs, charting a route toward their integration into ultralow-power optical switches, data-storage elements, and nanoscale sensors.
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All authors Elena Pinilla-Cienfuegos, Lucas Mascaró-Burguera, Ramón Torres-Cavanillas, J. Ignacio Echavarría, Alejandro Regueiro, Eugenio Coronado, Javier Hernandez-Rueda
Materials Science
Size-dependent transformation patterns in NiTi tubes under tension and bending: Stereo digital image correlation experiments and modeling
Aslan Ahadi, Elham Sarvari, Jan Frenzel et al. (+3 more)
The dependence of transformation pattern in superelastic NiTi tubes on tube outer diameter D and wall-thickness t is investigated through quasi-static uniaxial tension and large-rotation bending experiments. The
evolution of outer-surface strain fields is synchronized with global stress-strain and moment-
curvature responses using a multi-magnification, high-resolution stereo digital image correlation system at 0.5-2x magnifications. The transformation patterns exhibit systematic size-dependent behaviors. Under tension and for a specific D, as the diameter-to-thickness ratio D/t decreases, a decreasing number of fat/diffuse helical bands emerge, in contrast to sharp/slim bands in thin tubes. Consequently, the austenite-martensite front morphology transitions from finely-fingered to coarsely-fingered with decreasing D/t. Below a characteristic D/t, front morphology no longer exhibits patterning and phase transformation proceeds via propagation of a finger-less front. Moreover, the transformation pattern exhibits an interrelation between D and D/t, where a front possessing diffuse fingers is observed in a thin but small tube. Under bending, both the global moment-
curvature response and transformation pattern exhibit D- and D/t-dependence. While wedge-like martensite domains consistently form across all tube sizes, their growth is noticeably limited in smaller and thicker tubes due to geometrical constraints. A gradient-enhanced model of superelasticity is employed to analyze the distinct transformation patterns observed in tubes of various dimensions. The size-dependent behavior is explained based on the competition between bulk and interfacial energies, and the energetic cost of accommodating martensite fingers. By leveraging an axisymmetric tube configuration as a reference energy state, the extra energy associated with the formation of fingers is quantified.
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All authors Aslan Ahadi, Elham Sarvari, Jan Frenzel, Gunther Eggeler, Stanisław Stupkiewicz, Mohsen Rezaee-Hajidehi
Materials Science
Density functional investigations on 2D-Be2C as an anode for alkali Metal-ion batteries
Hetvi Jadav, Sadhana Matth and Himanshu Pandey
Metal-ion batteries are in huge demand to cope with the increasing need for renewable energy, especially in automobiles. In this work, we apply first-principle calculations to examine two-dimensional beryllium carbide (2D-Be2C) as a possible anode material for metal-ion (Na and K) batteries. 2D-Be2C is a
semiconductor and becomes metallic by adsorbing metal ions. Negative adsorption energy indicates stable adsorption on the monolayer of Be2C. Alkali metal
diffusion barrier and optimum path for minimum energy are studied within the framework of the climbing image nudged elastic band method. Here, six intermediate images are considered between the initial and final states. The lowest
diffusion barriers for a single adsorbed Na and K atom are 0.016 and 0.026 eV, respectively. A maximum open
circuit voltage of around 1 V is computed for K ions, whereas 0.5 V is for Na ions. Also, the maximum storage capacity of the Be2C monolayer is estimated at 1785 Ah/kg.
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Materials Science
Hexagonal BeX (X: S, Te) monolayer as potential electrode material for alkali metal-ion batteries: A DFT perspective
Hetvi Jadav, Sadhana Matth and Himanshu Pandey
Metal-ion batteries (MIBs) are essential for transitioning to a cleaner and more sustainable energy future. By employing the density functional formalism, we have investigated the hexagonal (h) monolayer of BeS and BeTe as electrode materials for alkali (Li and Na) MIBs. The structural and thermodynamic stability, adsorption of Li/Na atoms, density of states,
diffusion, and migration of atoms, as well as capacity, are systematically investigated. The structures of h-BeS and h-BeTe remain stable upon the adsorption of adatoms, resulting in improved electronic conductivity of these monolayers. The climbing image-nudged elastic band calculations estimate a low
diffusion barrier of 0.16 eV (0.01 eV) for Li (Na) in h-BeS and 0.20 eV (0.16 eV) for Li (Na) in h-BeTe. Additionally, a maximum storage capacity of 580 mAh g-1 for Li and 1305 mAh g-1 for Na in h-BeS, as well as 174 mAh g-1 for h-BeTe, is estimated for both metal ions.
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Materials Science
High-performance thermochromic multilayer coatings with W-doped VO2 nanoparticles dispersed in SiO2 matrix prepared on glass at a low temperature
Jaroslav Vlcek, Michal Kaufman, Elnaz M. Nia et al. (+5 more)
We report a high-performance thermochromic VO2-based coating prepared by using a three-step process, consisting of magnetron sputter depositions of SiO2 films and V-W films and their postannealing, on standard glass at a low substrate temperature of 350 {\deg}C without opening the
vacuum chamber to atmosphere. It is formed by four layers of W-doped VO2 nanoparticles dispersed in SiO2
matrix. The coating exhibits a transition temperature of 33 {\deg}C with an integral luminous transmittance of 65.4% (low-temperature state) and 60.1% (high-temperature state), and a modulation of the
solar energy transmittance of 15.3%. Such a combination of properties, together with the low temperature during preparation, fulfill the requirements for large-scale implementation on building glass and have not been reported yet.
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All authors Jaroslav Vlcek, Michal Kaufman, Elnaz M. Nia, Jiri Houska, Jiechao Jiang, Radomir Cerstvy, Stanislav Haviar, Efstathios I. Meletis
Materials Science
Lattice dynamics in chiral tellurium by linear and circularly polarized Raman spectroscopy: crystal orientation and handedness
Davide Spirito, Sergio Marras and Beatriz Martín-García
Trigonal tellurium (Te) has attracted researchers'
attention due to its transport and optical properties, which include electrical magneto-
chiral anisotropy,
spin polarization and bulk photovoltaic effect. It is the anisotropic and
chiral crystal structure of Te that drive these properties, so the determination of its crystallographic orientation and handedness is key to their study. Here we explore the structural dynamics of Te bulk
crystals by angle-dependent linearly polarized Raman spectroscopy and
symmetry rules in three different crystallographic orientations. The angle-dependent intensity of the modes allows us to determine the arrangement of the helical chains and distinguish between crystallographic planes parallel and perpendicular to the chain axis. Furthermore, under different configurations of circularly polarized Raman measurements and
crystal orientations, we observe the shift of two
phonon modes only in the (0 0 1) plane. The shift is positive or negative depending on the handedness of the
crystals, which we determine univocally by chemical etching. Our analysis of three different
crystal faces of Te highlights the importance of selecting the proper orientation and crystallographic plane when investigating the transport and optical properties of this material. These results offer insight into the
crystal structure and
symmetry in other anisotropic and
chiral materials, and open new paths to select a suitable
crystal orientation when fabricating devices.
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Materials Science · Cross-listed from cond-mat.soft
Salt crystallization and deliquescence triggered by humidity cycles in nanopores
Hugo Bellezza, Marine Poizat and Olivier Vincent
We study the response of materials with nanoscale pores containing sodium chloride solutions, to cycles of relative humidity (RH). Compared to pure fluids, we show that these sorption isotherms display much wider hysteresis, with a shape determined by salt crystallization and deliquescence rather than capillary condensation and Kelvin evaporation. Both deliquescence and crystallization are significantly shifted compared to the bulk and occur at unusually low RH. We systematically analyze the effect of pore size and salt amount, and rationalize our findings using confined thermodynamics, osmotic effects and classical nucleation theory.
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Materials Science
Influence of Hydrogen-Incorporation on the Bulk Electronic Structure and Chemical Bonding in Palladium
L. J. Bannenberg, F. García-Martínez, P. Lömker et al. (+6 more)
Palladium hydride is a model system for studying metal-hydrogen interactions. Yet, its bulk electronic structure has proven difficult to directly probe, with most studies to date limited to surface-sensitive photoelectron spectroscopy approaches. This work reports the first in-situ ambient-pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) study of hydrogen incorporation in Pd thin films, providing direct access to bulk chemical and electronic information at elevated hydrogen pressures. Structural characterisation by in-situ X-ray diffraction and
neutron reflectometry under comparable conditions establishes a direct correlation between hydrogen loading,
lattice expansion, and electronic modifications. Comparison with density functional theory (DFT) reveals how hydrogen stoichiometry and site occupancy govern the density of occupied states near the
Fermi level. These results resolve long-standing questions regarding PdH and establish AP-HAXPES as a powerful tool for probing the bulk electronic structure of metal hydrides under realistic conditions.
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All authors L. J. Bannenberg, F. García-Martínez, P. Lömker, R. Y. Engel, C. Schlueter, H. Schreuders, A. Navarathna, L. E. Ratcliff, A. Regoutz
Materials Science · Cross-listed from cond-mat.mes-hall
Single femtosecond laser pulse-driven ferromagnetic switching
Chen Xiao, Boyu Zhang, Xiangyu Zheng et al. (+18 more)
Light pulses offer a faster, more energy-efficient, and direct route to
magnetic bit writing, pointing toward a hybrid
memory and computing paradigm based on
photon transmission and
spin retention. Yet progress remains hindered, as deterministic, single-pulse optical toggle switching has so far been achieved only with ferrimagnetic materials, which require too specific a rare-earth composition and temperature conditions for technological use. In mainstream ferromagnet–central to spintronic
memory and storage–such bistable switching is considered fundamentally difficult, as
laser-induced heating does not inherently break time-reversal
symmetry. Here, we report coherent magnetization switching in ferromagnets, driven by thermal anisotropy torque with single
laser pulses. The toggle switching behavior is robust over a broad range of pulse durations, from femtoseconds to picoseconds, a prerequisite for practical applications. Furthermore, the phenomenon exhibits reproducibility in CoFeB/MgO-based
magnetic tunnel junctions with a high magnetoresistance exceeding 110%, as well as the scalability down to nanoscales with remarkable energy efficiency (17 fJ per 100-nm-sized bit). These results mark a notable step toward integrating opto-spintronics into next-generation
memory and storage technologies.
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All authors Chen Xiao, Boyu Zhang, Xiangyu Zheng, Yuxuan Yao, Jiaqi Wei, Dinghao Ma, Yuting Gong, Rui Xu, Xueying Zhang, Yu He, Wenlong Cai, Yan Huang, Daoqian Zhu, Shiyang Lu, Kaihua Cao, Hongxi Liu, Pierre Vallobra, Xianyang Lu, Youguang Zhang, Bert Koopmans, Weisheng Zhao
Materials Science · Cross-listed from physics.bio-ph
Spatial organization of biomass controls intrinsic permeability of porous systems
Wenqiao Jiao, David Scheidweiler, Nolwenn Delouche et al. (+2 more)
Biofilms in porous media critically influence hydraulic properties in environmental and engineered systems. However, a mechanistic understanding of how microbial life controls permeability remains elusive. By combining microfluidics, controlled pressure gradient and time-lapse microscopy, we quantify how motile and non-motile bacteria colonize a porous landscape and alter its resistance to flow. We find that while both strains achieve nearly identical total biomass, they cause drastically different permeability reductions - 78% for motile
cells versus 94% for non-motile
cells. This divergence stems from motility, which limits biomass spatial accumulation, whereas non-motile
cells clog the entire system. We develop a mechanistic model that accurately predicts permeability dynamics from the pore-scale biomass distribution. We conclude that the spatial organization of biomass, not its total amount, is the primary factor controlling permeability.
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All authors Wenqiao Jiao, David Scheidweiler, Nolwenn Delouche, Alberto Guadagnini, Pietro de Anna
Materials Science
The plastic flow of polycrystalline solids
Miguel Lagos
A polycrystalline solid is modelled as an ensemble of random irregular polyhedra filling the entire space occupied by the solid body, leaving no voids or flaws between them. Adjacent grains can slide with a relative velocity proportional to the local shear stress resolved in the plane common to the two sliding grains, provided it exceeds a threshold. The local forces associated to the continuous grain shape accommodation for preserving matter continuity are assumed much weaker. The model can be solved analytically and for overcritical conditions gives two regimes of deformation, plastic and superplastic. The plastic regime, from yield to fracture, is dealt with. Applications to nickel superalloys and stainless steels give impressive agreement with experiment. Most work of the last century relies on postulating pre–existent cracks and voids to explain plastic deformation and fracture. The present model gives much better results.
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Materials Science
First-principles design of excitonic insulators: A review
H. W. Qu, H. T. Liu and Y. C. Li
The excitonic
insulator (EI) is a more than 60-year-old theoretical proposal that yet remains elusive. It is a purely
quantum phenomenon involving the spontaneous generation of
excitons in
quantum mechanics and the spontaneous condensation of
excitons in
quantum statistics. At this point, the
excitons represent the ground state rather than the conventional excited state. Thus, the scarcity of candidate materials is a key factor contributing to the lack of recognized EI to date. In this review, we begin with the birth of EI, presenting the current state of the field and the main challenges it faces. We then focus on recent advances in the discovery and design of EIs based on the first-principles Bethe-Salpeter scheme, in particular the dark-
exciton rule guided screening of materials. It not only opens up new avenues for realizing excitonic instability in direct-gap and wide-gap
semiconductors, but also leads to the discovery of novel
quantum states of matter such as half-EIs and
spin-triplet EIs. Finally, we will look ahead to possible research pathways leading to the first recognized EI, both computationally and theoretically.
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Materials Science · Cross-listed from cond-mat.mes-hall
Theoretical Investigation of Anomalous Hall and Nernst Responses in Potassium Tri Vanadium Pentantimonide
Partha Goswami
We present a theoretical study of the anomalous Nernst and
Hall conductance in the Kagome metal potassium tri vanadium pentantimonide, based on a system
Hamiltonian incorporating nearest neighbour and complex next nearest neighbour hopping, Rashba
spin orbit coupling, an exchange field induced by
magnetic proximity, and a charge density wave potential. Our analysis reveals that the Nernst conductivity exhibits a non monotonic temperature dependence. It increases with temperature, reaches a pronounced peak, and subsequently declines at higher temperatures due to thermal broadening, which diminishes the influence of Berry
curvature. Notably, small shifts in the chemical potential can lead to dramatic changes in the Nernst signal enhancing its magnitude or even reversing its sign highlighting the system sensitivity to carrier density. We further explore the anomalous
Hall behaviour within this framework. The band structure hosts multiple bands with nonzero Berry
curvature, and preliminary Chern number calculations suggest weak topological features, namely, while not fully quantized, the system exhibits significant Berry
curvature accumulation. Upon introducing momentum space winding, implemented via a momentum dependent phase in the complex hopping terms to mimic orbital
magnetic flux, we observe that two bands acquire opposite Chern numbers. The remaining bands remain topologically trivial.
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Materials Science
High thermal conductivity of rutile-GeO$_2$ films grown by MOCVD: $52.9~\mathrm{W\,m^{-1}\,K^{-1}}$
Imteaz Rahaman, Michael E. Liao, Ziqi Wang et al. (+10 more)
Rutile germanium dioxide (r-GeO2) has recently emerged as a promising ultrawide-bandgap (UWBG)
semiconductor owing to its wide bandgap (~4.4-5.1 eV), ambipolar doping potential, and high theoretical thermal conductivity. However, experimental data on the thermal conductivity of r-GeO2 epitaxial layers have not been reported, primarily due to challenges in phase control and surface roughness. Here, we report a high thermal conductivity of 52.9 +/- 6.6 W m^-1 K^-1 for high-quality (002) r-GeO2 films grown by metal-organic chemical vapor deposition (MOCVD) and characterized using time-domain thermoreflectance (TDTR). The phase control was achieved through a seed-driven stepwise crystallization (SDSC) approach, and the surface roughness was significantly reduced from 76 nm to 16 nm (locally as low as 1 A) via chemical mechanical polishing (CMP). These results highlight the promise of r-GeO2 as a UWBG
oxide platform for power electronics applications.
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All authors Imteaz Rahaman, Michael E. Liao, Ziqi Wang, Eugene Y. Kwon, Rui Sun, Botong Li, Hunter D. Ellis, Bobby G. Duersch, Dali Sun, Jun Liu, Mark S. Goorsky, Michael A. Scarpulla, Kai Fu
Materials Science
Crossover between intrinsic and temperature-assisted regimes in spin-orbit torque switching of antiferromagnetic order
Takumi Matsuo, Tomoya Higo, Daisuke Nishio-Hamane et al. (+7 more)
Intensive studies have been made on antiferromagnets as candidate materials for next generation
memory bits due to their ultrafast dynamics reaching picosecond time scales. Recent demonstrations of electrical bidirectional switching of
antiferromagnetic states have attracted significant
attention. However, under the presence of significant Joule heating that destabilizes the
magnetic order, the timescales associated with the switching can be limited to nanoseconds or longer. Here, we present the observation of a crossover in the switching behavior of the
chiral antiferromagnet Mn3Sn by tuning the
magnetic layer thickness. While Joule heating interferes with switching in thicker devices, we find clear signatures of an intrinsic
spin-orbit torque mechanism as the thickness is reduced, avoiding the heating effect. The suppression of heating enables switching without significant attenuation of the readout signal using pulses shorter than those required by temperature-assisted mechanisms. The crossover into the
spin-orbit torque switching behavior clarifies the potential for achieving ultrafast switching as expected from the picosecond
spin dynamics of antiferromagnets. Our results lay the groundwork for designing
antiferromagnetic memory devices that can operate at ultrafast timescales.
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All authors Takumi Matsuo, Tomoya Higo, Daisuke Nishio-Hamane, Takuya Matsuda, Ryota Uesugi, Hanshen Tsai, Kouta Kondou, Shinji Miwa, Yoshichika Otani, Satoru Nakatsuji
Materials Science · Cross-listed from cond-mat.soft
Plastic or Viscous? A Reappraisal of Yielding in Soft Matter
Yogesh M. Joshi and Alexander Ya. Malkin
Many soft jammed materials, such as pastes, gels, concentrated emulsions, and suspensions, possess a threshold stress, known as yield stress, that must be exceeded to cause permanent deformation or flow. In rheology, the term plastic flow is commonly used to describe continuous flow (unbounded increase in strain with time) that a material undergoes above a yield stress threshold. However, in solid mechanics, plasticity refers to irreversible but finite, rate-independent deformation (strain that does not evolve with time). In addition, many soft materials exhibit viscosity bifurcation, a prominent thixotropic signature, which further complicates the definition and interpretation of yield stress. The threshold stress at which viscosity bifurcation occurs is also termed a yield stress, even though deformation below this threshold is not purely elastic, while above this threshold, the material flows homogeneously with a constant shear rate. This paper revisits these critical issues by analyzing the rheological and solid mechanics perspectives on plasticity. The insights presented here are intended to address certain terminological ambiguities for interpreting flow in soft jammed materials.
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Materials Science · Cross-listed from cond-mat.str-el
Time-Resolved Photoemission Spectroscopy of Quantum Materials Using High Harmonic Generation: Probing Electron-Phonon Interactions and Non-Equilibrium Dynamics
Takeshi Suzuki and Kozo Okazaki
Recent advancements in ultrafast
laser systems and high harmonic generation (HHG) techniques have enabled time-resolved photoemission spectroscopy on femtosecond timescales, opening up unprecedented opportunities to explore
quantum materials in both time and momentum space. In this review, we present recent representative studies utilizing HHG-
laser-based time- and angle-resolved photoemission spectroscopy for a variety of
quantum materials. We particularly highlight electron-
phonon interactions and non-
equilibrium dynamics in time and frequency domain, through which rich information about non-
equilibrium electron-
phonon couplings and related phenomena has been clearly revealed.
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