Hasil untuk "Atomic physics. Constitution and properties of matter"

S. Yu. Mezhevych, O. A. Ponkratenko, Yu. M. Stepanenko et al.

Recently published experimental angular distributions of the reaction 13С(11В, 10В)14С at Еlab(11B) = 45.0 MeV for transitions to the ground states of exit channel nuclei, were analyzed within coupled-reaction-channels method (CRC), applying for 10В + 14С interaction the potentials for systems 10В + 12-20С that were obtained by means of the double-folding method (DF) using modelled shapes for the distributions of nucleons in 10В and 12-20С nuclei. This research aimed to investigate the influence of the surface structure of 12-20С isotopes, reflected accordingly in the constructed potentials for the interaction of 10В + 12-20С, on the results of CRC-calculations and their agreement with experimental data. The difference of CRC cross sections for the direct transfer of a neutron, as the main reaction mechanism, was found to be small when applying DF-potentials calculated for systems 10В + 12-16С in the exit channel of this reaction. Only with DF-potentials for 10В + 17-20С systems used in the exit channel of the reaction 13С(11В, 10В)14С a more notable difference of CRC cross sections against the experimental data and those used for the system 10В + 14С was observed, what originates from more diffuse density distributions of nucleons modelled on the surfaces of isotopes 17-20С in comparison with 14С. As CRC-calculations of transfer reactions are affected by strong couplings between different channels, what can deteriorate the investigation of the influence of slight differences in the shapes of DF-potentials in the interaction region, the measurements of angular distributions for the elastic and inelastic scattering of unstable 15-20С isotopes are desirable, as far as possible, for the investigation of their internal structure and isotopic differences.

E. G. Khidher, A. H. Taqi

In this study, we presented the centroid energies (ECEN), scaled energies (ES), and constrained energies (ECON) of the isoscalar (T = 0) giant monopole and quadrupole resonances and isovector (T = 1) giant dipole resonances in 56,60,68Ni. Utilizing 16 distinct Skyrme-type effective nucleon-nucleon interactions often employed in the literature, these energies were computed using the completely self-consistent Hartree - Fock based on random phase approximation theory. We compared our theoretical calculations with the available experimental data. We primarily examined the effects of nuclear matter (NM) features, including the symmetry energy at saturation density, the effective mass (m*/m), and the nuclear matter incompressibility coefficient (KNM), on ECEN, ES, and ECON. We analyzed the sensitivity by determining the Pearson linear correlation coefficient between the calculated energies and NM properties. Also, we presented and discussed the values of ECEN, ES, and ECON as a function of atomic mass A.

H. Aboud, I. T. Al-Alawy

Glass systems of the form (70-x)B2O3-10ZnO-10PbO-10CdO-xBi2O3 (with x = 0 to 20 mol%) were prepared by the standard melt-quenching approach and characterized. The role of varying Bi2O3 doping contents on the radiation shielding, dose rate, and stopping power of the proposed glasses was examined. Various radiation shielding properties, such as exposure buildup factors, gamma-ray constants and dose rates, and total neutron removal cross-section, were estimated. The x-ray diffractometer patterns of the samples showed their amorphous characteristics. Glass density was increased from 5.34 to 6.95 g/cm3, and the energy band gap was reduced with the increase in Bi2O3 doping contents. In addition, both mass attenuation numbers and effective atomic numbers of the samples (calculated using Phy-X software) in the gamma-ray energy range of 0.015 to 15 MeV were increased with the increase in Bi2O3 contents. With the increase in Bi2O3 doping, the gamma-ray shielding, stopping power, and neutron removal cross-section of the glasses were improved. This new glass composition was asserted to be a good candidate for radiation shielding applications.

Xia Liu, Geng Liu, Hao-Kai Zhang et al.

Variational quantum algorithms (VQAs) are expected to establish valuable applications on near-term quantum computers. However, recent works have pointed out that the performance of VQAs greatly relies on the expressibility of the ansatzes and is seriously limited by optimization issues, such as barren plateaus (i.e., vanishing gradients). This article proposes the state-efficient ansatz (SEA) for accurate ground state preparation with improved trainability. We show that the SEA can generate an arbitrary pure state with much fewer parameters than a universal ansatz, making it efficient for tasks like ground state estimation. Then, we prove that barren plateaus can be efficiently mitigated by the SEA and the trainability can be further improved most quadratically by flexibly adjusting the entangling capability of the SEA. Finally, we investigate a plethora of examples in ground state estimation where we obtain significant improvements in the magnitude of the cost gradient and the convergence speed.

Sergei Urazhdin

An unexpectedly large transient magnetization induced by circularly polarized ferroelectric phonons was recently observed in a nonmagnetic insulator SrTiO3 [Nature 628, 534 (2024)]. We use a minimal molecular orbital model to demonstrate two electronic contributions to this effect. An atomic orbital contribution arises from the pumping of orbital angular momentum of Ti by chiral motion of coordinating oxygen atoms. An additional inter-atomic contribution is associated with the transient circulating current around the oxygen atoms, resulting in efficient dressing of phonons by electron dynamics. The insights provided by our model may facilitate the development of ultrafast magnetization control and orbitronic sources.

Prashant Thakur, Tuhin Malik, T. K. Jha

In recent years, researchers have become increasingly interested in understanding how dark matter affects neutron stars, helping them to better understand complex astrophysical phenomena. In this paper, we delve deeper into this problem by using advanced machine learning techniques to find potential connections between dark matter and various neutron star characteristics. We employ Random Forest classifiers to analyze neutron star (NS) properties and investigate whether these stars exhibit characteristics indicative of dark matter admixture. Our dataset includes 32,000 sequences of simulated NS properties, each described by mass, radius, and tidal deformability, inferred using recent observations and theoretical models. We explore a two-fluid model for the NS, incorporating separate equations of state for nucleonic and dark matter, with the latter considering a fermionic dark matter scenario. Our classifiers are trained and validated in a variety of feature sets, including the tidal deformability for various masses. Based on confusion matrices, these classifiers can identify NS with admixed dark matter with approximately 17% probability of misclassification. In particular, we find that additional tidal deformability data do not significantly improve the precision of our predictions. This article also delves into the potential of specific NS properties as indicators of the presence of dark matter. Radius measurements, especially at extreme mass values, emerge as particularly promising features. The insights gained from our study will guide future observational strategies and enhance dark matter detection capabilities. According to this study, neutron stars at 1.4 and 2.07 solar masses have radii that strongly suggest dark matter in neutron stars more likely than just hadronic composition, based on NICER data from pulsars PSR J0030+0451 and PSR J0740+6620.

Rene Bodker Christensen, Petar Popovski

In this article, we show that a pair of entangled qubits can be used to compute a product privately. More precisely, two participants with a private input from a finite field can perform local operations on a shared, Bell-like quantum state, and when these qubits are later sent to a third participant, the third participant can determine the product of the inputs, but without learning more about the individual inputs. We give a concrete way to realize this product computation for arbitrary finite fields of prime order.

M. Verseils, P. Hemme, D. Bounoua et al.

Abstract Electromagnons (Electroactive spin wave excitations) could prove to be decisive in information technologies but they remain fragile quantum objects, mainly existing at low temperatures. Any future technological application requires overcoming these two limitations. By means of synchrotron radiation infrared spectroscopy performed in the THz energy range and under hydrostatic pressure, we tracked the electromagnon in the cupric oxide CuO, despite its very low absorption intensity. We demonstrate how a low pressure of 3.3 GPa strongly increases the strength of the electromagnon and expands its existence to a large temperature range enhanced by 40 K. Accordingly, these two combined effects make the electromagnon of CuO under pressure a more ductile quantum object. Numerical simulations based on an extended Heisenberg model were combined to the Monte-Carlo technique and spin dynamics to account for the magnetic phase diagram of CuO. They enable to simulate the absorbance response of the CuO electromagnons in the THz range.

Evyatar Tulipman, Erez Berg

Abstract The Wiedemann-Franz (WF) law, stating that the Lorenz ratio L = κ/(T σ) between the thermal and electrical conductivities in a metal approaches a universal constant $${L}_{0}={\pi }^{2}{k}_{B}^{2}/(3{e}^{2})$$ L 0 = π 2 k B 2 / ( 3 e 2 ) at low temperatures, is often interpreted as a signature of fermionic Landau quasi-particles. In contrast, we show that various models of weakly disordered non-Fermi liquids also obey the WF law at T → 0. Instead, we propose using the leading low-temperature correction to the WF law, L(T) − L 0 (proportional to the inelastic scattering rate), to distinguish different types of strange metals. As an example, we demonstrate that in a solvable model of a marginal Fermi-liquid, L(T) − L 0 ∝ − T. Using the quantum Boltzmann equation (QBE) approach, we find analogous behavior in a class of marginal- and non-Fermi liquids with a weakly momentum-dependent inelastic scattering. In contrast, in a Fermi-liquid, L(T) − L 0 is proportional to − T 2. This holds even when the resistivity grows linearly with T, due to T − linear quasi-elastic scattering (as in the case of electron-phonon scattering at temperatures above the Debye frequency). Finally, by exploiting the QBE approach, we demonstrate that the transverse Lorenz ratio, L x y  = κ x y /(T σ x y ), exhibits the same behavior.

Venkata Satya Surya Phaneendra Pydimarri, Timothy R. Field

The dynamics of an identical pair of entangled spin-1/2 particles, both subjected to the same random magnetic field, are studied. The dynamics of the pure joint state of the pair are derived using stochastic calculus. An ensemble of such pure states is combined using the modified spin joint density matrix, and the joint relaxation time for the pair of spin-1/2 particles is obtained. The dynamics can be interpreted as a special kind of correlation involving the spatial components of the Bloch polarization vectors of the constituent entangled spin-1/2 particles.

Shiyu Fan, Sobhit Singh, Xianghan Xu et al.

Abstract Hafnia (HfO2) is a promising material for emerging chip applications due to its high-κ dielectric behavior, suitability for negative capacitance heterostructures, scalable ferroelectricity, and silicon compatibility. The lattice dynamics along with phononic properties such as thermal conductivity, contraction, and heat capacity are under-explored, primarily due to the absence of high quality single crystals. Herein, we report the vibrational properties of a series of HfO2 crystals stabilized with yttrium (chemical formula HfO2: xY, where x = 20, 12, 11, 8, and 0%) and compare our findings with a symmetry analysis and lattice dynamics calculations. We untangle the effects of Y by testing our calculations against the measured Raman and infrared spectra of the cubic, antipolar orthorhombic, and monoclinic phases and then proceed to reveal the signature modes of polar orthorhombic hafnia. This work provides a spectroscopic fingerprint for several different phases of HfO2 and paves the way for an analysis of mode contributions to high-κ dielectric and ferroelectric properties for chip technologies.

A. I. Lypska, V. I. Nikolaev, V. A. Shytiuk et al.

The results of radioecological monitoring of the research sites located on the drained areas and the coastal of the ChNPP cooling pond are presented. The features of the spatial distribution of the exposure dose rate, the density of soil radionuclide contamination by the emergency radionuclides were determined. The content of incorporated radionuclides in representatives of the genera Myodes and Sylvaemus were studied, the individual and interspecies variability of 137Cs and 90Sr levels in animals within the limits of one research site was determined. Currently, the indicators of radioactive contamination of biota in the drained areas of the cooling pond are within the variation of those values that are characteristic of most areas of the Chornobyl exclusion zone.

Luis A. Anchordoqui, Akitaka Ariga, Tomoko Ariga et al.

The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.

M. A. Bludov, I. V. Khyzhniy, E. V. Savchenko et al.

The formation of self-oscillations of temperature and concentration of radicals in an electron-irradiated methane film at low temperatures has been investigated experimentally and theoretically. Self-oscillations arise due to the activation nature of diffusion and radical recombination processes. Self-oscillations were studied experimentally by measuring the desorption of particles from an irradiated sample and theoretically by solving the kinetic equations for defects in a methane sample. Concentration self-oscillations of two types of particles have been found and investigated; namely, hydrogen atoms and CH3 radicals formed during the irradiation of methane by electrons. It is shown that with an increase in the irradiation intensity, the oscillation periods decrease, and the calculation value are of the order of magnitude observed in the experiment. A model of a manifestation of the self-oscillation of hydrogen molecule concentration during desorption is presented.

D. M. Holiaka, S. E. Levchuk, V. A. Kashparov et al.

Statistical and graphical interpretation of 90Sr vertical distributions in soil profiles up to a depth of 1.0 m was presented based on the study of the typical Scots pine stands forest at 14 experimental sites within the Chernobyl exclusion zone. Significant differences were found between 90Sr activity distribution in soil profiles collected at different sites. The part of 90Sr activity below of a depth of 30 cm varied from 15 to 71 %. 90Sr transfer factors from soil to anatomical structures of the stem wood were estimated based on values of soil contamination density, which were calculated for the depth of 0.3 and 1.0 m. The statistically significant correlation between the transfer factors of 90Sr to stem wood (heartwood, sapwood) and its vertical distributions in soil profiles have not been observed. Among the forest inventory parameters for pine stands only the average diameter of trees significantly correlated with 90Sr transfer factors to stem wood.

Karl Nelson, Chad Fertig, Paul Hamilton et al.

We describe an ultra-compact ($\sim 10$ cm$^3$ physics package) inertial sensor based on atomic matter waves that are guided within an optical lattice during almost the entire interferometer cycle. We demonstrate large momentum transfer (LMT) of up to 8$\hbar k$ photon momentum with a combination of Bragg pulses and Bloch oscillations with scalability to larger numbers of photons. Between momentum transfer steps, we maintain the atoms in a co-moving optical lattice waveguide so that the atoms are in free space only during the Bragg pulses. Our guided matter wave approach paves the way for atomic inertial sensing in dynamic environments in which untrapped atoms would otherwise quickly collide with the walls of a miniature chamber.

Gerhard Gompper, Roland G. Winkler, Thomas Speck et al.

Activity and autonomous motion are fundamental in living and engineering systems. This has stimulated the new field of active matter in recent years, which focuses on the physical aspects of propulsion mechanisms, and on motility-induced emergent collective behavior of a larger number of identical agents. The scale of agents ranges from nanomotors and microswimmers, to cells, fish, birds, and people. Inspired by biological microswimmers, various designs of autonomous synthetic nano- and micromachines have been proposed. Such machines provide the basis for multifunctional, highly responsive, intelligent (artificial) active materials, which exhibit emergent behavior and the ability to perform tasks in response to external stimuli. A major challenge for understanding and designing active matter is their inherent nonequilibrium nature due to persistent energy consumption, which invalidates equilibrium concepts such as free energy, detailed balance, and time-reversal symmetry. Unraveling, predicting, and controlling the behavior of active matter is a truly interdisciplinary endeavor at the interface of biology, chemistry, ecology, engineering, mathematics, and physics. The vast complexity of phenomena and mechanisms involved in the self-organization and dynamics of motile active matter comprises a major challenge. Hence, to advance, and eventually reach a comprehensive understanding, this important research area requires a concerted, synergetic approach of the various disciplines.

Liesbeth M. C. Janssen

Active glassy matter has recently emerged as a novel class of non-equilibrium soft matter, combining energy-driven, active particle movement with dense and disordered glass-like behavior. Here we review the state-of-the-art in this field from an experimental, numerical, and theoretical perspective. We consider both non-living and living active glassy systems, and discuss how several hallmarks of glassy dynamics (dynamical slowdown, fragility, dynamical heterogeneity, violation of the Stokes-Einstein relation, and aging) are manifested in such materials. We start by reviewing the recent experimental evidence in this area of research, followed by an overview of the main numerical simulation studies and physical theories of active glassy matter. We conclude by outlining several open questions and possible directions for future work.

A. V. Viatkina, D. Antypas, M. G. Kozlov et al.

We estimate the relative contribution of nuclear structure and new physics couplings to the parity non-conserving spin-independent effects in atomic systems, for both single isotopes and isotopic ratios. General expressions are presented to assess the sensitivity of isotopic ratios to neutron skins and to couplings beyond standard model at tree level. The specific coefficients for these contributions are calculated assuming Fermi distribution for proton and neutron nuclear densities for isotopes of Cs, Ba, Sm, Dy, Yb, Pb, Fr, and Ra. The present work aims to provide a guide to the choice of the best isotopes and pairs of isotopes for conducting atomic PNC measurements.

Chao Zhang, Feixiang Hao, Guanyin Gao et al.

Condensed matter physics: enhancing superconductivity in TiO The cubic titanium monoxide undergoes a superconducting transition at 2 K in its bulk form. However, access to the superconductivity mechanism is blocked by the lack of TiO single crystals or epitaxial films. Now, Prof. Xiaoguang Li and his co-workers from University of Science and Technology of China and other institutions in China and USA report a success in growing cubic TiO thin films epitaxially on α-Al2O3 single crystals oriented along the c-axis utilizing a pulsed laser deposition technique. Both magnetization and transport measurements suggest the type-II superconducting nature at a record high critical temperature of 7.4 K. Further characterization indicates that the increasing pressure weakens the superconductivity. This work opens an avenue towards the understanding and manipulation of superconducting behavior in titanium-based oxide superconductors.