Physical Sciences

Abstract: High-entropy transition metal carbides combine ultrahigh hardness, excellent thermal stability, and intrinsic structural disorder, making them attractive for extreme-environment applications. Using density functional theory in the generalized gradient approximation (GGA-PBE) as implemented in the ABINIT package, we systematically calculate the electronic structure and bulk modulus B of a series of (TiZrHf-X)C compositions (X = Sc, V, Nb, Ta, Mo, W) with varying average d-electron count per metal site (ndest). A 24-atom rock-salt (B1) supercell with numerical-annealing relaxation of atomic positions is employed. The calculated DOS for group IV carbides TiC, ZrC, and HfC reveals a strikingly similar electronic structure: in all three cases the Fermi level is located within a wide pseudogap—responsible for the wide carbon nonstoichiometry range—and falls precisely on a small local peak resembling a Van Hove singularity, which promotes vacancy formation even at low temperatures. Qualitatively similar DOS profiles are found for all HECs studied, indicating that this electronic stabilization mechanism persists in multi-component systems. The bulk modulus increases monotonically with ndest from 209±1 GPa for (TiZrHfSc)C to 269±2 GPa for (TiZrHfW)C. At fixed ndest, heavier homologue metals (Ta > Nb > V; W > Mo) yield higher B due to greater core-electron Pauli repulsion. A single metal vacancy reduces B by approximately 21–35 GPa and simultaneously increases configurational entropy, suggesting that metal vacancies function as an additional thermodynamic stabilizing component of the high-entropy compound.

Abstract: A rheological replacement model of a coupled-field continuum induces a constitutive 1-form whose primitive on a star-shaped reversible state space is a thermodynamic potential from which the full constitutive set is recovered by differentiation. The existence of the primitive is equivalent to a single symmetry condition on the constitutive Jacobian; in coupled-field problems that condition is exactly the family of Maxwell relations between the coupled effects. Truesdell's principle of equipresence and the thermodynamic driving forces of the internal variables are consequences of the same construction; the residual dissipation inequality appears as the remaining part of the Clausius--Duhem inequality after all process-independent contributions have been absorbed into the potential.

Abstract: We find a mapping between the attractive Fermi-Hubbard model and the repulsive Bose-Hubbard model at finite temperature and at imaginary chemical potential μ=iθ. We show, by using a large N-expansion, that the partition functions of the two models are related by a simple shift θ→θ+π. This condition maps the BCS–BEC crossover of attractive fermions to a Bose–Fermi crossover (fermion-like occupation) of repulsive bosons. Central feature of this correspondence plays the thermal kernel g(βE,ϕ), whose analytic continuation gB(βE,ϕ)=gF(βE,ϕ+π) governs the bosonic and fermionic sectors. Interestingly, we are able to find that the special angles ϕ=2π/3,4π/3 for fermions correspond to ϕ=π/3,5π/3 for bosons, marking the boundaries of a universal thermal window. We further argue that the present mechanism shows that fermionization can occur at finite interaction strength through a thermodynamic effect induced by the imaginary chemical potential. This suggests that it is a new way of fermionization (not a change in statistics but a fermion-like behaviour) unlike the Tonks–Girardeau limit, where fermionization arises from an infinite repulsive interaction and anyonic or Floquet-engineered systems where transmutation emerges from modified statistics or dynamics. Essentially, the phase ϕ is a statistical parameter; by twisting the thermal phase, it generates fermion-like behaviour without hard-core constraints or infinite repulsion but only by using thermodynamics. We derive the gap equation and number equation for the bosonic model, highlighting the role of the imaginary chemical potential as a statistical regulator. Our results provide a unified framework for understanding crossovers in interacting lattice systems.

Abstract: We propose a mechanically programmable nanoscale Chern valve based on an altermagnet–topologicalinsulator (AM–TI) heterostructure, where thin altermagnetic electrodes impose an anisotropic exchange mass on the surface states of a few-quintuple-layer topological-insulator channel. Periodic strain, delivered for example by integrated piezoelectric or surface-acoustic-wave actuators, modulates the inplane crystalline phase of the altermagnetic order and renormalizes the twofold and fourfold interfacial exchange harmonics through zeroth-order Bessel functions. This amplitude-selective renormalization produces re-entrant Chern plateaus, Hall and thermoelectric polarity inversions, and quantized adiabatic charge pumping with winding number changing from 0 to 2. For representative RuO₂/Bi₂Se₃ parameters, the induced gaps remain in the meV range, while MHz mechanical driving places the system deeply within the adiabatic regime. The predicted signatures are directly accessible in nanoscale Hall-bar geometries through the strain-amplitude dependence of transverse Hall response, gate-tracked thermoelectric Hall response, and the collapse of topological sectors near Bessel zeros. The proposed mechanism therefore provides a low-frequency, on-chip route to mechanically controlled topological transport in nano-spintronic AM–TI devices, without optical Floquet driving or net magnetization reversal.

Abstract: We report the first successful synthesis of millimeter-sized single crystals of high-entropy perovskite manganites with the composition (La_0.25Pr_0.25Sm_0.25Gd_0.25)_1-xCa_xMnO₃ (x = 0.3, 0.4, 0.5). Single crystals exceeding 2 mm in size were grown via a flux method using a PbF₂/PbO/B₂O₃ system. The X-ray diffraction patterns exhibit only (0k0) series reflections, indicating strong preferred orientation and high-quality single-crystal character. Scanning electron microscopy reveals dense, grain-boundary-free surfaces. Energy-dispersive X-ray spectroscopy elemental mapping shows uniform distribution of all constituent elements without detectable segregation or secondary phases, confirming the formation of a true high-entropy solid solution in single-crystal form. To the best of our knowledge, based on the publicly searchable literature, this is the first report of bulk single-crystalline high-entropy perovskite oxide. This breakthrough provides a much-needed single crystal experimental platform for systematically investigating the intrinsic magnetotransport mechanisms of compositionally complex strongly correlated oxides, free from grain-boundary interference.

Abstract: Ultrastrong magnetic fields, ranging from 100~T to 1,000~T, are generated exclusively by destructive pulsed magnets. While various generation methods exist, this review focuses on the Single-Turn Coil (STC) and Electromagnetic Flux Compression (EMFC) techniques, which provide optimal environments for high-precision measurements in materials science. First, we present recent technological breakthroughs in the EMFC method that have successfully achieved fields exceeding 1,000~T. We then describe specialized measurement infrastructures for magneto-optics, magnetization, and magneto-transport, highlighting the development of miniaturized all-plastic cryostats and custom sample holders designed for the dual extremes of cryogenic temperatures and megagauss fields. Representative physical phenomena revealed through these techniques are discussed, including quantum phase transitions in frustrated magnets, Aharonov--Bohm effects in carbon nanotubes, and semiconductor-to-metal transitions in strongly correlated systems. Furthermore, we address emerging measurement platforms such as magnetostriction, specific heat, and ultrasound velocity. Throughout this review, we emphasize the instrumentation and experimental refinements that ensure reliable data acquisition in the ultrastrong pulsed field regime.

Abstract: This article describes the development of a compact and affordable variable temperature NMRinstrument designed primarily to measure dynamic molecular motions in solids and liquids. The instrument consists of Lab-Tools’ Mk4 palm-top time-domain NMR spectrometer fitted with a Peltier-cooled variable temperature probe inside a shimmed Halbach magnet. Measurement of NMR relaxation times T₁, T₂, T_1ρ are possible over the temperature range −20^◦C to 70^◦C with cooling and heating rates, and data acquisition controlled from an integrated mini-PC. The overall footprint of the instrument is roughly that of a shoe box making both in-the-field and bench-top measurements possible. Applications of this instrument include measuring the pore size distribution in porous rocks, the viscosity of oils and tars trapped in porous rock, the properties of polymers, and the viscosity of the liquid components of foods (e.g. fruits, vegetables and seeds). Results of test measurements on calibrated oils and olive oil are presented together with measurements of the molecular mobility in a sold polymer.

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: By making periodic thru-holes in a suspended film, the phonon system can be modified. Motivated by the BCS theory, the technique -- so-called phonon engineering -- was applied to a metallic niobium sheet. It was found that its electrical resistance dropped to zero at 175 K, and the zero-resistance state persisted up to 290 K in the subsequent warming process. Despite the initial motivation, neither these high transition temperatures nor the phase transition with thermal hysteresis can be accounted for by the BCS theory. Therefore, we abandon the BCS theory. Instead, it turns out that the metallic holey sheet is partly oxidized to form a niobium-oxygen square lattice, which has points of resemblance to a copper-oxygen plane, the fundamental component of cuprate high-T_c superconductors. Therefore, the pairing mechanism underlying this study should be related to that of cuprate high-T_c superconductors, which we may not yet understand. In addition to the electrical results of zero resistance, the holey sheet exhibited a decrease in magnetization upon cooling, i.e., the Meissner effect. Moreover, the remnant magnetization was clearly detected at 300 K, which can only be attributed to persistent currents flowing in a superconducting sample. Thus, this study meets the established criteria for a conclusive demonstration of true superconductivity. Finally, the superconducting transition with the unambiguous thermal hysteresis is discussed. According to Halperin, Lubensky, and Ma, or HLM for short, any superconducting transition must always be first order with thermal hysteresis because of the intrinsic fluctuating magnetic field. The HLM theory is very compatible with the highly oriented system harboring two-dimensional superconductivity.

Abstract: Attenuated total reflection terahertz time-domain spectroscopy (THz-TDS ATR) was employed to investigate the dielectric response of water–acetone mixtures over the full molar concentration range. The ATR configuration enabled stable measurements in a controlled and nearly closed environment, minimizing acetone evaporation and allowing reliable characterization of this highly volatile binary system. The complex dielectric function, retrieved in the 0.4–1.6 THz range, was analyzed by means of a double Cole–Cole model, which provides a more consistent description of the mixtures than a simple Debye-based approach. A strongly nonlinear dependence on composition was observed, with the highest sensitivity in the water-rich region, where even small amounts of acetone produce a marked change in both the real and imaginary parts of the dielectric function. The extracted parameters indicate that acetone primarily suppresses the slow, cooperative relaxation channel associated with the hydrogen-bond network of water, whereas the faster channel remains comparatively less affected, consistent with its more local intermolecular origin. The evolution of the Kirkwood–Fröhlich correlation factors and of the broadening parameters further supports a progressive transition from a highly correlated hydrogen-bonded liquid to a structurally heterogeneous and weakly cooperative dipolar environment. These results demonstrate that THz-TDS ATR is a sensitive tool for probing intermolecular reorganization in aqueous binary mixtures and provide a physically grounded framework for the detection of acetone and other volatile hydrogen-bond-active species in water-based systems.

Abstract: The presence of Cu³⁺ cations and oxygen vacancies (VO) in the electrospun CuO nanofibers was identified by X-ray photoelectron spectroscopy (XPS) from the Cu 2p₃/₂ and O 1s core-level spectra, respectively. A Cu³⁺-related superlattice was observed using nano-beam electron diffraction (NBD). The chemical composition of the two samples thermally treated at 600 °C (CuO600) and 700 °C (CuO700) was further corroborated using the geometrical topofactor method. For comparison, bulk CuO was also analyzed. XPS peak fitting of the Cu 2p and O 1s regions was performed using an SVSC-type background and two-parameter Tougaard function. X-ray diffraction (XRD) confirmed the presence of the tenorite and cuprite phases and enabled crystallite size estimation (FullProf). The average crystallite size ranged from 20.59 ± 0.06 nm to 31.06 ± 0.06 nm, in good agreement with High Resolution Transmission Electron Microscope, HR-TEM, measurements (14.98 ± 0.34 nm and 36.10 ± 0.94 nm). Therefore, we identify that Cu³⁺ and oxygen vacancies in these nanofibers plays a crucial role in optimizing their future applications in the electronic and catalytic fields.

Abstract: Low temperature photoluminescence (PL) has been studied under hydrostatic pressure and under varying excitation powers in three samples of single In0.17Ga0.83N quantum wells with different widths: 2.6 nm, 5.2 nm, and 10.4 nm. Transitions involving ground states were strong in the 2.6 nm well, weak in the 5.2 nm well, and absent in the 10.4 nm well. Pressure coefficients of PL lines have been used to estimate the electric field in the wells. In the widest well the field seems to be fully screened (at high excitation powers). Simulations involving Poisson and Schrodinger equations allowed to identify the experimental PL lines. Pressure evolution of the PL spectra agreed with the simula-tion.

Abstract: Co²⁺-doped CsPbI₃ nanocrystals (NCs) (CsPbI₃:xCo, x = 0, 0.05, and 0.10 mol%) were synthesized in situ within a borosilicate glass matrix by the fusion method followed by controlled thermal treatment at 500 °C for 6–24 h. Transmission electron microscopy images showed quasi-spherical NCs formed within the glass matrix with mean diameters ranging from 6.3 to 8.4 nm, consistent with diffusion-mediated growth under glass nanoconfinement. Energy-dispersive X-ray spectroscopy confirmed the presence of Co within the NCs regions. X-ray diffraction patterns confirm the exclusive stabilization of the cubic α-phase across all compositions, with a systematic shift of the (200) reflection to greater angles with increasing Co content, evidencing B-site lattice contraction due to the substitution of Pb²⁺ by Co²⁺. Optical absorption and photoluminescence spectra demonstrate that Co²⁺ incorporation enhances the δ-phase emission in the as-prepared condition, consistent with defect passivation, and that progressive thermal treatment stabilizes band-edge excitonic emission near ~1.74 eV without disrupting the fundamental optical response of the α-CsPbI₃ host. Crystal field theory and Tanabe–Sugano analysis for d⁷ ions in Td symmetry yielded Δ = 5032 cm⁻¹ and B = 725 cm⁻¹ in the as-prepared state, evolving to Δ = 4428 cm⁻¹ and B = 805 cm⁻¹ after thermal treatment, confirming the tetrahedral coordination of Co²⁺ and significant metal–iodide covalency. These results position CsPbI₃:xCo NCs embedded in glass as robust platforms for glass-integrated photonic applications.

Abstract: Considering the uniqueness and simplicity of our 4G model of strong and electroweak nuclear binding energy formula, the traditional Coulombic repulsion concept in nuclear binding scheme can be reconsidered or replaced by a fundamental electroweak interaction framework. Close to stable mass numbers, for medium and heavy atomic nuclides, A and Z being the mass number and proton number, approximate formula for nuclear binding energy is, BE={A-0.0016[(A2+Z2)/2]-A(1/3)-0.5}10.1 MeV where the factor can be considered as the nuclear electroweak stability coefficient. Approximate stable mass number associated with any proton number Z can be understood with, As=2Z+0.0016(2Z)2. Building on this foundation, the potential mechanism of cold nuclear fusion-assumed to be governed by strong and weak interactions, can be more effectively explored. Continued research may enable the development of clean, green and safe cold nuclear energy technologies capable of generating approximately 1 MeV of energy per fusion event. For experimental purposes, stable isotopes of light to medium-heavy elements with atomic numbers ranging from Z=1 to 30 can be targeted. Material selection point of view, it is expected that, cold nuclear material, should have the ability of absorbing hydrogen atoms or neutrons. Upon absorbing the hydrogen atom, nuclide experiences isotopic or isobaric conversion, increase in nuclear binding energy and increase in nucleons’ kinetic energy. Higher the difference of nuclear binding energy, lower the expected thermal energy and vice versa. In our recent papers, we have taken Iron and Magnesium as the cold nuclear fuels. It needs further study.

Abstract: We investigated the structural, magnetic, magnetocaloric, and magnetotransport properties of Ni₅₀Mn₃₅In₁₅ Heusler alloys by partial substitution of Ni with 3 at.% Bi (Ni₄₇Bi₃Mn₃₅In₁₅) and Si (Ni₄₇Si₃Mn₃₅In₁₅) synthesized by arc-melting. X-ray diffraction confirms a predominant L₂₁ cubic structure (space group Fm-3m), while SEM/EDX verifies compositional homogeneity. Temperature-dependent magnetization measurements reveal that the Bi-substituted alloy exhibits a first-order magnetostructural transition associated with the martensitic transformation, followed by a second-order ferromagnetic–paramagnetic transition near the Curie temperature. In contrast, the Si-substituted alloy shows a single second-order transition with negligible thermal hysteresis, indicating suppression of the martensitic phase. The Curie temperature decreases from 324 K for the parent alloy to 313 K and 286 K for the Bi- and Si-substituted alloys, respectively. A maximum magnetic entropy change of 6.0 Jkg^-1K^-1 and 4.5 Jkg^-1K^-1 is obtained under an applied magnetic field change of 50 kOe for the Bi- and Si-substituted alloys, respectively, with corresponding relative cooling power values of 303 Jkg^-1 and 345 Jkg^-1. These results demonstrate that lattice expansion (Bi) and contraction (Si) distinctly modify Mn–Mn exchange interactions, enabling tunable magnetocaloric performance in Ni–Mn–In Heusler alloys.

Abstract: High-temperature superconductivity remains an open problem in condensed matter physics. While conventional and many unconventional approaches attribute superconductivity primarily to pairing mechanisms, experimental observations—including pseudogap behavior, strange-metal transport, and nanoscale inhomogeneity— suggest that pairing alone may be insufficient. We introduce a coordination-based framework in which superconductivity arises from the global organization of internal degrees of freedom associated with local electronic configurations. These degrees of freedom, modeled as effective pseudospin variables, form a system-spanning coordination manifold that stabilizes dissipationless transport, with pairing emerging as a secondary manifestation. We show that internal coordination induces an instability of the incoherent transport state, leading to global phase coherence. At the effective level, this yields a scaling relation for the transition temperature, T_c∼gm²/a_ψ′, linking superconductivity to the strength of coordination. The framework accounts for the separation between pseudogap onset and superconducting transition, the anomalous transport properties of strange metals, and nanoscale electronic inhomogeneity, and predicts distinct coherence scales and nontrivial vortex-core structure. These results suggest that optimizing coordination of internal degrees of freedom may provide an alternative route to enhancing superconductivity.

Abstract: Using the molecular dynamics method, the compression of nickel nanoparticles with a nanocrystalline structure at low temperatures was simulated. The influence of the nanoparticle size (from 2 to 20 nm) and the average grain size within it (from 2 to 8 nm) on the compressive strength and on the strain at which the maximum stress is reached was investigated. In addition, the stability of the nanocrystalline structure of the nanoparticles was studied as a function of temperature and grain size. It is shown that the smaller the diameter of the nanocrystalline particle, the higher the compressive strength and the strain at which the maximum stress is reached. A decrease in grain size leads to a reduction in compressive strength, which is associated with the main mechanism of plastic deformation of nanocrystalline nanoparticles, namely grain boundary sliding. At the first stage of deformation, the entire particle structure typically rotates until the maximum value of the stress vector projection onto the preferred slip plane is reached, which, in the case of a nanocrystalline structure, is determined by the mutual orientation of the grain boundaries. Grain boundaries elongated approximately along a single plane represent, in this case, the preferred slip plane.

Abstract: This work addresses the quasi-static behaviour of fibre-reinforced materials whose response is based on a hyperelastic formulation augmented by viscous and damage-like effects. A transversely isotropic constitutive model is developed within the framework of an internal scalar variable, enabling the reversible description of material damage while ensuring objectivity, thermodynamic admissibility and polyconvexity of the stored-energy function. The isotropic contribution is constructed from a generalised Ciarlet model, whereas the anisotropic part accounts for a family of elastic fibres embedded in a viscoelastic matrix, interpreted through a simple mixture theory. The resulting constitutive equations are implemented in Abaqus/Standard via a UMAT subroutine, and their rate form is derived consistently with the Zaremba–Jaumann objective stress rate. The performance of the model is examined by means of finite element simulations, including homogeneous tests in uniaxial strain and simple shear, relaxation and creep problems, and an inflation-like problem. The results demonstrate the capability of the model to capture strain-rate sensitivity, creep, stress relaxation and energy dissipation, as well as non-uniform deformation patterns, while highlighting its current limitation in representing permanent deformations.

Abstract: Luminescent gadolinium oxide nanoparticles doped with europium were synthesized through a precipitation reaction using gadolinium and europium nitrates as precursors. The europium- doped gadolinium oxide nanoparticles were incorporated first: into a Gel matrix of silicon dioxide; and second: mixing with Polymethyl Methacrylate. Both processes are synthesized by the simultaneous hydrolysis of tetraethyl orthosilicate and polymerization of 3-(Trimethoxysilyl) propyl methacrylate. The solid samples obtained are round in shape with a size of about 2.5 cm, which makes it easy to handle to test different applications. The inclusion of Gd2O3:Eu3+ nanoparticles increases the level of absorbance in the ultraviolet region, which allows for improved emission of the material at a wavelength of around 609 nm. Furthermore, it enables easy doping of the material and the fabrication of thin films and monoliths with potential optical applications.

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.