Abstract: In this work, we develop machine-learned moment tensor potentials (MTPs) to simulate the static and dynamic structural properties in Al_xGa_1−xN and related materials. The potentials are trained on DFT-calculated data for forces, stresses, and energies obtained from random atomic displacements and cell deformations. MTP-calculated physical properties, including lattice and elastic constants, thermal expansion, harmonic and anharmonic vibrational properties, and the thermal conductivity, are benchmarked against first-principles results and experimental data. The comparisons testify to the very high accuracy achieved by the machine-learned potentials despite the massively reduced computational effort. Additionally, the impact of various aspects of the MTP training procedure is examined.

Abstract: The equation of state of crystals under external stress, derived years ago based on the principles of statistical physics, was re-derived in the same way, but for non-crystals under general external stress and temperature. Its relationship with the macroscopic mechanical equilibrium condition was also discussed.

Abstract: Nanoscale conductors and interfaces frequently exhibit anomalous AC transport behavior and enhanced superconducting critical temperatures that are not fully captured by conventional electron-phonon descriptions. In this exploratory work, we consider a complementary mechanism based on the possible inertial response of a Z₃-graded vacuum sector to time-varying electromagnetic fields. Within this speculative phenomenological framework, surface criticality is tentatively proposed as a mechanism that may drive high-energy vacuum modes toward low-energy collective excitations at surfaces and interfaces, giving rise to an approximate coherence length ξ_vac∼70 nm. This geometric length scale, if physically meaningful, could influence effective conductivity in the non-local regime and might contribute to observed features such as high-frequency skin depth saturation and interface-driven T_c enhancement. Preliminary evaluations based on the algebraic structure suggest qualitative consistency with certain experimental observations in high-purity metals and nanowire systems, although we emphasize that these consistencies may be coincidental. The framework is offered as a tentative, exploratory perspective on mesoscopic anomalies, with the aim of stimulating further discussion and investigation into possible connections between algebraic high-energy structures and low-energy quantum materials phenomena.

Abstract: Negative capacitance (NC) has been reported across a wide range of physical systems, yet its interpretation has remained fragmented due to the absence of a unified conceptual framework. Existing explanations—spanning ferroelectric free‑energy curvature, tunneling transport, plasmonic resonances, and electronic compressibility—have often been treated as unrelated or even contradictory. This review resolves these inconsistencies by demonstrating that all manifestations of NC arise from —non‑synchronization—between external excitation and internal response. We classify NC into three fundamental categories: temporal mismatch, originating from delays or inertia in charge or polarization dynamics; spatial mismatch, caused by nonuniform field or mode distributions; and quantitative mismatch, resulting from intrinsic parameter reversal such as negative curvature or negative compressibility. Despite their diverse physical origins, these mechanisms share the same mathematical signature (C_eff=∂Q/∂V< 0). Organizing NC within this unified framework clarifies long‑standing ambiguities, connects previously isolated research fields, and establishes a systematic foundation for engineering NC in electronic, photonic, and quantum devices. The framework further highlights tunnel‑current‑induced NC as a distinct single‑particle mechanism, expanding the scope of NC beyond ferroelectricity and collective modes. Overall, this work positions NC not as a singular anomaly but as a universal response class emerging from the interplay between excitation and internal dynamics.

Abstract: We demonstrate that dopant inhomogeneity strongly suppresses thermal conductivity in Cd/Eu co-doped, non-polar a-oriented ZnO films grown on r-plane sapphire (Al₂O₃) by plasma-assisted molecular beam epitaxy. Structural characterization by θ-2θ XRD confirms a-oriented ZnO without detectable secondary phases. Cross-sectional SEM shows continuous films with well-defined interfaces, and SIMS depth profiling verifies Cd/Eu incorporation through the film thickness and a sharp Zn/O drop at the substrate interface. Optical transmittance and Tauc analysis reveal composition-dependent shifts of the absorption edge and band gap. Cross-plane thermal transport was measured at room temperature using frequency-domain photothermal infrared radiometry (PTR) and analyzed by fitting the complex PTR amplitude and phase with a multilayer heat-diffusion model. The extracted thermal conductivity spans ~3.7 - 6.3 Wm-1K-1. The lowest k values correlate with increased defect non-uniformity, consistent with enhanced phonon scattering and reduced effective cross-plane heat transport.

Abstract: In a previous work [Bakonyi et al., Eur. Phys. J. Plus 137, 871 (2022)], in-plane magnetoresistance results were reported on a thin strip-shaped foil sample of nanocrys-talline (nc) Ni metal. These studies have been by now complemented with the measure-ment of the temperature dependence of the resistivity as well as the field dependence of the resistivity and the Hall effect on the same sample at 3 K and 300 K in polar magnetic fields up to 140 kOe, i.e., with the magnetic field perpendicular to the strip plane. Due to the strong contribution of the grain-boundary scattering in the nc state, the residual re-sistivity was about 11 % of the room-temperature value. The polar magnetoresistance (PMR) showed a similar behavior to the previously reported transverse magnetoresistance (TMR), yielding an anisotropic magnetoresistance (AMR) value in good agreement with the AMR previously deduced from the in-plane MR data. As to the Hall effect, the results for the ordinary (Ro) and the anomalous (Rs) Hall coefficient fitted rather well into the rather dispersed reported data of bulk Ni at both temperatures. However, a closer look of the Rs values for nc-Ni revealed that at 300 K it is larger and at 3 K it is smaller than the corresponding bulk Ni values obtained on samples with the same zero-field resistivity as our nc-Ni foil. It will be discussed briefly that these deviations may be attributed to the nanocrystalline state containing a large density of grain boundaries.

Abstract: The Johnson–Mehl–Avrami–Kolmogorov (JMAK) formalism provides a classical framework for describing polymer crystallization kinetics; its applicability under finite-domain confinement requires quantitative assessment. In this work, the influence of one-dimensional geometric restriction on cylindrical growth in polymer thin films is investigated using a stochastic Monte Carlo approach. The model considers site-saturated nucleation on randomly distributed cylindrical nanofibers with constant radial growth velocity under hard-wall boundary conditions. Crystallization kinetics were evaluated through automated segmented regression of the double-logarithmic JMAK representation. Under confinement, the Avrami plot departs from single-slope linearity and exhibits two successive quasi-linear regimes characterized by effective parameter pairs (n₁, ln k₁) and (n₂, ln k₂). The primary exponent n₁ remains thickness-independent, consistent with early-stage radial expansion prior to boundary interaction. The secondary exponent n₂ displays a non-monotonic dependence on reduced film thickness, reflecting the competing influence of wall-induced truncation and inter-fiber impingement on late-stage transformation. These results support a geometric interpretation in which finite-domain constraints modify effective growth dimensionality and provide a reproducible framework for analyzing dual-regime Avrami behavior in confined crystallization systems.

Abstract: Kinetic Rate Equation (kRE) modeling is widely used to simulate defect and impurity evolution in solids over experimentally relevant time and length scales. However, conventional kRE formulations include only random-position sink strengths, which adequately describe trapping of defects created at random lattice sites but fail to capture the enhanced retrapping of defects released directly adjacent to traps during detrapping or dissociation events. This omission leads to systematic errors, including underestimated thermal desorption (TDS) peak temperatures and incorrect kinetic parameters when fitting to experimental data. In this work, we derive for the first time analytical expressions for the adjacent sink strength, including correction for finite impurity diffusion jump length. We provide a practical implementation strategy for integrating these expressions into kRE simulations. Comparisons with kinetic Monte Carlo (kMC) benchmarks demonstrate that adjacent sink strengths dominate the retrapping probability and are essential for reproducing the correct temperature dependence of TDS release peaks. Simulations that employ only random sink strengths can still be tuned to match TDS spectra; however, the resulting fitted trapping energies, detrapping frequencies, and diffusion parameters are often physically inconsistent. The adjacent sink strength formulation introduced here significantly improves the predictive capability of kRE modeling, enabling accurate multiscale simulations of defect and impurity behavior in materials. This framework also establishes a foundation for future extensions, including adjacent sink strengths associated with extended defects such as dislocations and grain boundaries, offering new opportunities to resolve persistent discrepancies between experimental and simulated trapping energetics.

Abstract: The effect of water on the dynamics and ionic conductivity of the ionic liquids 1-ethyl-1-methylpyrrolidinium levulinate ([C₂C₁Pyr]Lev) and 1-butyl-1- methylpyrrolidinium levulinate ([C₄C₁Pyr]Lev) was investigated using differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS) over a wide temperature range. Although both ILs share the same levulinate anion, water induces markedly different dynamical responses depending on cation structure. In both systems, water acts as a plasticizer, lowering the glass transition temperature; however, the extent of plasticization and the resulting relaxation dynamics are cation-dependent. Stronger water–cation interactions are observed in [C₂C₁Pyr]Lev, whereas in [C₄C₁Pyr]Lev, water primarily disrupts alkyl-chain packing, enhancing ionic mobility. Increasing hydration shifts the main relaxation to higher frequencies and increases liquid fragility, while translational ionic motion remains partially decoupled from structural relaxation. These results demonstrate that water plays a cation-specific and mechanistically distinct role in levulinate-based ILs, providing new insights into hydration-controlled glassy dynamics and charge transport relevant for the design of IL-based electrolytes under non-anhydrous conditions.

Abstract: The microscopic pairing mechanism in unconventional superconductors remains elusive, largely because the extreme flatness of the superconducting band often obscures key energy-momentum dispersion features observed in angle-resolved photoemission spectroscopy. In this work, we re-examine high-resolution dispersion data from cuprates (Bi2212 and Bi2201) and iron-based superconductors (monolayer FeSe) to test the predictions of a newly proposed chiral electron-hole (CEH) pairing mechanism. Unlike Cooper pairs in BCS-like theories that form a single quasiparticle band with a smooth back-bending dispersion, CEH pairs exhibit a distinct two-band structure in quasiparticle dispersion with sharp cusps at the back-bending points. Our analysis identifies clear empirical signatures of these CEH-predicted features, concluding that quasiparticle dispersions in these strongly correlated materials deviate significantly from BCS-like behavior. Further comprehensive and targeted experimental strategies are proposed to definitively resolve the subtle dispersion features and rigorously test the CEH model for unconventional superconductivity.

Abstract:

The superconducting transition temperature of CaC₆ is investigated within the Roeser–Huber (RH) formalism using both rhombohedral and hexagonal crystallographic representations. While these two descriptions are crystallographically equivalent, they differ in their geometric construction of superconducting paths and near-atom environments. In the rhombohedral representation, only translationally closed Ca–Ca vectors consistent with the primitive lattice are considered, yielding three symmetry-distinct RH paths. In the hexagonal representation, the same superconducting channels are expressed in an expanded conventional cell, where some paths appear as unfolded or symmetry-related sublattice connections. For each representation, the RH path lengths and effective near-atom counts are evaluated and used to compute the superconducting transition temperature. The rhombohedral description yields $T_c^{\rm(calc)} = 10.35$ K, while the hexagonal representation gives $T_c^{\rm(calc)} = 10.91$ K, both in good agreement with the experimental value $T_c^{\rm(exp)} = 11.5$ K. The difference between the calculat\( {The superconducting transition temperature of CaC$_6$ is investigated within the Roeser–Huber (RH) formalism using both rhombohedral and hexagonal crystallographic representations. While these two descriptions are crystallographically equivalent, they differ in their geometric construction of superconducting paths and near-atom environments. In the rhombohedral representation, only translationally closed Ca–Ca vectors consistent with the primitive lattice are considered, yielding three symmetry-distinct RH paths. In the hexagonal representation, the same superconducting channels are expressed in an expanded conventional cell, where some paths appear as unfolded or symmetry-related sublattice connections. For each representation, the RH path lengths and effective near-atom counts are evaluated and used to compute the superconducting transition temperature. The rhombohedral description yields $T_c^{\rm(calc)} = 10.35$ K, while the hexagonal representation gives $T_c^{\rm(calc)} = 10.91$ K, both in good agreement with the experimental value $T_c^{\rm(exp)} = 11.5$ K. The difference between the calculated values amounts to approximately 5.4\%. These results show that the underlying RH superconducting channels and their near-atom environments are representation independent, while minor quantitative differences in $T_c^{\rm(calc)}$ arise from metric redistribution of equivalent paths. This directly confirms that the RH formalism captures intrinsic structural features of superconductivity rather than artifacts of unit-cell representation. \)d values amounts to approximately 5.4\%. These results show that the underlying RH superconducting channels and their near-atom environments are representation independent, while minor quantitative differences in $T_c^{\rm(calc)}$ arise from metric redistribution of equivalent paths. This directly confirms that the RH formalism captures intrinsic structural features of superconductivity rather than artifacts of unit-cell representation.

Abstract: In this work, the so-called characteristic function method is proposed as a new approach to describe and interpret the diffusion process with interacting adsorbates in terms of the surface coverage. In this context, the intermediate scattering function is shown to be a characteristic function of probability theory which is also the generating function of the moments and cumulants of the jump probability distribution. The theoretical analysis carried out here consists of reviewing very briefly firstly the case of non-interacting adsorbates or very low surface coverages and extending secondly this method to low and intermediate surface coverages. As a direct consequence of this analysis, it is shown that the static structure factor is also a characteristic function of the adsorbate separation distances.

Abstract: The detection of SF₆ decomposition products is essential for diagnosing insulation faults in gas-insulated switchgear. Using first-principles density functional theory, this study investigates the adsorption behavior of five characteristic gases (H₂S, SO₂, SOF₂, SO₂F₂, and SF₆) on pristine and vanadium-doped graphene/MoS₂ (GMV) heterostructures to evaluate their potential for gas sensing applications. Pristine graphene/MoS₂ exhibits weak physisorption toward all target molecules, with low adsorption energies and negligible charge transfer, indicating insufficient sensitivity for practical use. To address this limitation, a V-doped graphene/MoS₂ heterostructure is proposed, wherein vanadium atoms are incorporated into the graphene lattice to introduce active centers and modulate interfacial charge transfer. The results demonstrate that H₂S, SO₂, and SOF₂ preferentially adsorb atop the V site via local covalent interactions, with significantly enhanced adsorption energies (up to −0.388 eV for SO₂) and shortened distances. In contrast, SO₂F₂ and SF₆ adsorb near electron-depleted carbon regions driven by electrostatic attraction. Charge density difference and Bader charge analyses reveal pronounced charge redistribution upon SO₂ and SF₆ adsorption, while density of states analysis confirms orbital hybridization near the Fermi level, suggesting possible chemical bond formation. Notably, adsorption of SO₂ and SF₆ substantially reduces the density of states at near Fermi level, indicating a measurable modulation of surface conductivity. These findings establish V-doped graphene/MoS₂ as a promising sensing material for selective detection of SF₆ decomposition products, offering a viable strategy for advancing online monitoring technologies in power systems.

Abstract: This work presents an extensive investigation on the synthesis, structural characterization, optical evaluation, and device applications of Er-doped and Er-Yb co-doped ZnO thin films prepared via a citric acid-assisted sol-gel process combined with spin coating. Pd/ZnO:Er and (Er/Yb)/n-Si/Au-Sb Schottky barrier diodes were fabricated using resistive evaporation technique for precise contact deposition. The impact of Er and Er-Yb codoping on structural, optical, and electrical properties, as well as device performance was compared in detail, providing insights into rare-earth codoping strategies for high-performance optoelectronic devices. X-ray diffraction (XRD) analysis confirmed the retention of the hexagonal wurtzite structure in all films, with minor shifts in peak positions indicating successful doping. Optical characterization revealed a slight widening of the bandgap in co-doped films, attributed to the dopant effect. Electrical measurements of SBDs demonstrated improved rectification ratios, lower ideality factors, and higher barrier heights in co-doped films compared to undoped Er doped counterparts. These findings underscore the efficacy of Er/Yb co-doping in modulating the properties of ZnO thin films for advanced optoelectronic applications.

Abstract: The constant external electric field, applied to a semiconductor nanostructure, changes the symmetry. It can be cylindrical symmetry, for the field parallel to the z-axis, or a symmetry breaking, for the field parallel to the x-y plane. The symmetry changes affect the optical properties of the system, which are subject of the presented considerations. Below we present a theoretical calculation of optical functions for CdSe Nanoplatelets with excitons, in an external homogeneous electric field. We consider various configurations, with the external field perpendicular and parallel to the platelet planes. With the help of the real density matrix approach, we calculate the linear electro-optical functions of CdSe nanoplatelets, taking into account the effect of a dielectric confinement on excitonic states. The impact of platelet geometry (thickness, lateral dimension), and on the applied field strength, on the spectrum, is discussed.

Abstract: We perform Density Functional Theory calculations to determine adsorption energies of small gas molecules ($\mathrm{H}_2$, $\mathrm{N}_2$, NO, and CO) on defective, vacancy-laden, black phosphorene. Different configurations of single and double vacancies in the monolayer structure are considered, together with several possible adsorption sites onto them. The van der Waals interaction is considered for the exchange-correlation functional. This research aims to provide fundamental insights into how atomic vacancies can be engineered to tune phosphorene's surface reactivity, offering a broader understanding of its multifaceted applications.

Abstract: The development of high-performance anode materials is essential to overcome the limitations associated with conventional graphite electrodes in lithium-ion batteries, and perovskite oxides emerge as promising alternatives due to their structural flexibility and defect chemistry. In this work, the potential of LaSrCoFeO₃ perovskite (LSCF) thin films as anode materials is investigated, with particular emphasis on the effect of the post-deposition annealing atmosphere. LSCF thin films were deposited by dc magnetron sputtering and then thermal-treated at 600 °C in air and vacuum. The structural, electrical and electrochemical characterizations show that vacuum annealing promotes a more efficient crystallization, leading to larger crystallites (~ 240 nm), and to reduced oxidation due to the formation of oxygen vacancies. This reduced state significantly reduces electrical conductivity to ~10-6 Ω·cm. When evaluated as a half-cell anode, the vacuum-annealed films exhibit a theoretical specific capacity of 121 mAh·g-1, high reversibility with anodic and cathodic charge ratio Qa/Qc ≈ 1 and a good cyclic stability, with a loss of discharge capacity of less than 10%. Raman spectroscopy confirmed that the film structure remains unchanged upon the electrochemical tests, evidencing their stability. These results show that the annealing atmosphere is a determining parameter to optimize the electrochemical performance of LSCF thin films, reinforcing their potential as anodes for future lithium-ion batteries.

Abstract: We theoretically investigate the influence of uniaxial distortion on the stability of square skyrmion crystals, which are described as double-$Q$ spin textures composed of two orthogonal spiral modulations, in noncentrosymmetric magnets. An effective spin model incorporating momentum-resolved frustrated exchange interactions and Dzyaloshinskii-Moriya (DM) interactions is analyzed using simulated-annealing calculations at low temperatures. The results reveal that uniaxial distortion drives a transformation from the double-$Q$ square skyrmion crystal to a single-$Q$ tilted conical spiral or vertical spiral state. The low-temperature phase diagrams further show that the stability region of the skyrmion crystal expands with increasing the magnitude of the DM interaction, making the phase more robust against the uniaxial anisotropy between exchange interactions parallel and perpendicular to the distortion axis. This study provides insight into how uniaxial strain and DM interactions cooperatively influence the formation and stability of skyrmion crystal phases in noncentrosymmetric magnetic systems.

Abstract: The influence of a non-resonant intense laser field on the optical absorption and Raman scattering processes in ZnO/Mg0.2Zn0.8O quantum wells is theoretically investigated. It is shown that the dressing field significantly modifies the confinement potential and reshapes the electronic wave functions, leading to tunable shifts in intersubband transition energies and changes in the dipole matrix elements. These laser-induced effects produce notable variations in the absorption spectrum and strongly modulate the Raman differential cross section and Raman gain. Under the application of the non-resonant laser field, the Raman gain is enhanced by almost a factor of four, whereas off-resonant pumping results in much weaker but still field-dependent responses. The results demonstrate that intense laser fields provide an effective tool to dynamically control the optical and Raman properties of ZnO-based quantum well structures.

Abstract: Non-equilibrium materials often exhibit a complex interplay between reversible elastic responses and irreversible processes such as viscous dissipation, structural relaxation, and aging. Classical constitutive models typically describe these behaviors using a single temporal variable, which can obscure the distinct physical mechanisms involved and require empirical memory kernels to account for history dependence. In this work, we address this limitation by introducing a temporal duality framework in which material behavior is governed by two coupled time regimes: a reversible time coordinate associated with elastic, time-symmetric dynamics, and an irreversible time coordinate associated with dissipative, aging, and time-asymmetric evolution. This dual-time formulation enables a unified description of viscoelasticity, memory effects, and aging, while providing structural clarity to the thermodynamic origins of irreversibility. Classical models are recovered as limiting cases, and illustrative examples show how the framework can reproduce stress–relaxation and aging behaviors commonly observed in polymers and disordered materials. This approach offers a new pathway for interpreting and modeling time-dependent behavior in non-equilibrium systems without relying on phenomenological assumptions.