Strong Atomic Interactions Research Articles

First-principles investigation of Cu/Ti-TM/Si (TM=W, Ru) interfaces: Role of Ti-TM binary alloys as diffusion barrier layers

This study employs first-principles calculations to investigate the role of Ti-TM (TM=W, Ru) binary alloys as diffusion barrier layers in Cu/Ti-TM/Si interfaces, which are critical for enhancing the performance and reliability of microelectronic devices. The calculated results reveal that TiRu and Ti4W12 alloys exhibit exceptional stability and low contact resistance, outperforming traditional Cu/Si interfaces. The introduction of these alloys into the interface structure results in a reduced Cu s-d coupling effect, which is pivotal for inhibiting Cu diffusion. Additionally, the presence of pseudogap features and enhanced electron distribution at the interface indicate strong atomic interactions, contributing to the formation of covalent bonds and further improving barrier properties. The findings suggest that TiRu and Ti4W12 alloys are promising candidates for diffusion barrier layers, offering a balance of low contact resistance, thermal stability, and effective Cu diffusion inhibition. Therefore, from the results, it is concluded that the formation of the new interface structure will improve performance in various aspects, and thus the strategy can be applied in various directions, such as new energy materials, electronic materials, and so on. In addition, the combination of the previous work and the present work suggests that Ti-based alloys have the potential to be used as diffusion barrier materials.

Trimethylamine-N-oxide depletes urea in a peptide solvation shell

Trimethylamine-N-oxide (TMAO) and urea are metabolites that are used by some marine animals to maintain their cell volume in a saline environment. Urea is a well-known denaturant, and TMAO is a protective osmolyte that counteracts urea-induced protein denaturation. TMAO also has a general protein-protective effect, for example, it counters pressure-induced protein denaturation in deep-sea fish. These opposing effects on protein stability have been linked to the spatial relationship of TMAO, urea, and protein molecules. It is generally accepted that urea-induced denaturation proceeds through the accumulation of urea at the protein surface and their subsequent interaction. In contrast, it has been suggested that TMAO's protein-stabilizing effects stem from its exclusion from the protein surface, and its ability to deplete urea from protein surfaces; however, these spatial relationships are uncertain. We used neutron diffraction, coupled with structural refinement modeling, to study the spatial associations of TMAO and urea with the tripeptide derivative glycine-proline-glycinamide in aqueous urea, aqueous TMAO, and aqueous urea-TMAO (in the mole ratio 1:2 TMAO:urea). We found that TMAO depleted urea from the peptide's surface and that while TMAO was not excluded from the tripeptide's surface, strong atomic interactions between the peptide and TMAO were limited to hydrogen bond donating peptide groups. We found that the repartition of urea, by TMAO, was associated with preferential TMAO-urea bonding and enhanced urea-water hydrogen bonding, thereby anchoring urea in the bulk solution and depleting urea from the peptide surface.

Normal mode description of phases of matter: Application to heat capacity

Understanding thermodynamics in liquids at the atomic level is challenging because of strong atomic interactions and lack of spatial symmetry. Recent prior theoretical works have focused on describing heat capacity of liquids in terms of phonon-like excitations but often rely on fitting factors and assumptions. In this work, we propose characterizing various phases in terms of instantaneous normal modes (INMs) of structural snapshots from molecular dynamics simulations of single-element systems over wide ranges of temperature and pressure. We use the INMs to build a mode-level microscopic description of heat capacity and demonstrate that heat capacity of liquids can be described by a combination of both solidlike and gaslike degrees of freedom, leading to a more unified framework to fundamentally describe heat capacity of all three phases of matter: solid, liquid, and gas. Published by the American Physical Society 2024

Exploring synergistic sintering factors and nanopore regeneration of calcium-based thermochemical energy storage materials

Calcium-based thermochemical energy storage is essential for high-temperature solar energy utilization. However, performance decay is inevitable in repeated calcination/carbonation cycles, even for modified materials. In this study, the effects of synergistic sintering factors on performance decay are investigated, including chemical reaction, temperature and CO2 atmosphere. More importantly, rather than complicating the initial preparation process of the anti-sintering composites to achieve higher stability, a regeneration method is proposed to repair the nanopores of sintered composites and recover their performances. After using citric acid to dissolve materials with heavily sintered morphologies and reconstruct their porous structures, the energy storage densities of both the co-doped and benchmark materials increase by 2–4 times. The regenerated Al/Mg co-doped composite also shows high cyclic stability in subsequent long-term cycles. Furthermore, DFT calculations illustrate the strong atomic interaction between CaO and dopants. The economic analysis reveals that the regeneration costs of the co-doped composites are approximately one-half of their synthesis costs, making them a cost-efficient choice for long-term industrial application. This work expands the limited perspectives of current modification research on improving cyclic stability. It can guide the actual industrial applications of thermochemical energy storage, thus enhancing material reutilization and realizing costs reduction.

Enhancement of electrocatalytic performance of Janus In2SSe monolayer for oxygen evolution reaction by the introduction of N

Non-metallic atom doping as efficient oxygen evolution reaction (OER) electrocatalysts has attracted much interest. In this work, the feasibility of N doped Janus In2SSe monolayers as an OER electrocatalyst is systematically investigated using first-principles calculations. The results suggest that the N substitution with high spin states for the S/Se atom in the Janus In2SSe monolayer can effectively enhance the electrocatalytic reactivity of adsorbed intermediates. The NS-In2SSe monolayer exhibit outstanding OER catalytic performance with small overpotential of 0.687 V. Moreover, the strong atomic interactions between the N dopant and intermediates can be contributed to the hybridization between the O- and N-p orbitals. Through the analysis of crystal orbital Hamilton population (COHP), the adsorption strength of OH species on the NS-In2SSe monolayer is stronger than that on the NSe-InSe monolayer, leading that the NS-In2SSe monolayer possesses a higher OER electrocatalytic activity. The fourth electron reaction step becomes exothermic when the real solution environment is considered, meaning that the desorption of O2 becomes easier under aqueous solution conditions. This work demonstrates the possibility of N doped Janus In2SSe monolayer as electrocatalyst and also offers new insights into designing SACs constructed by non-metal atoms.

A Python program to draw energy level diagram and to calculate quantum defects, the high lying Rydberg level

Rydberg atoms have strong and adjustable atomic interactions that can be tweaked by choosing different states with various principal quantum numbers or orbital angular momentum. They are highly used in quantum information applications. Furthermore, these atoms have long lifetimes and many possible energy levels, and their separations enable coupling to electromagnetic fields with frequencies ranging over six orders of magnitude. We studied some properties of these atoms and have developed a python program; the program gives two options. Firstly, it calculates energies of elements in s, p, d, and f orbitals and draws an energy level diagram of the element listed in the program. Secondly, it gives an option for calculating energy and quantum defects of atoms and ions, either listed or not listed in the program and generates their graphs accordingly. There are 21 elements in the database whose energy level diagrams could be drawn. The database can be extended by adding more elements.

Facilitation-Induced Transparency and Single-Photon Switch with Dual-Channel Rydberg Interactions

We investigate facilitation-induced transparency (FIT) enabled by strong and long-range Rydberg atom interactions between two spatially separated optical channels. In this setting, the resonant two-photon excitation of Rydberg states in a target channel is conditioned by a single Rydberg excitation in a control channel. Through the contactless coupling enabled by the Rydberg interaction, the optical transparency of the target channel can be actively manipulated by steering the optical detuning in the control channel. By adopting a dressed-state picture, we identify two different interference pathways, in which one corresponds to Rydberg blockade and an emergent one results from facilitation. We show that the FIT is originated from the Rydberg interaction and the quantum interference effect between the two pathways, which is different from conventional electromagnetically induced transparency realized by single-body laser-atom coupling. We find that the FIT in such a dual-channel setting is rather robust, insensitive to changes of systemic parameters, and can be generalized to multichannel settings. Moreover, we demonstrate that such a FIT permits the realization of controllable single-photon switches, which also paves a route to detect Rydberg facilitation by using optical absorption spectra. Our study contributes to current efforts in probing correlated many-body dynamics and developing single-photon quantum devices based on Rydberg atom ensembles.

Pressure weakening unusual-caged dynamics of La80Al20 metallic glass-forming liquid

Caged dynamics is the precursor of β-relaxation and is part of the complex relaxation dynamics of metallic glasses. However, limited by the lack of suitable experimental techniques, the pressure dependence of the caged dynamics of glass-forming metallic liquids and its underlying mechanism are still an open question to date. An unusual caged dynamics manifests a sudden drop near 0.1 ps in the partial non-Gaussian parameter of Al atoms in metallic alloy La80Al20 liquid was recently found by molecular dynamics simulations. The present work investigates the caged dynamics of the La80Al20 liquid with strong atomic interactions under different pressures again by molecular dynamics simulations. It is found that the dominant polyhedra are transformed from the stable icosahedral-like polyhedra to the unstable ones that are compatible with crystal symmetry, resulting in the promotion of the rearrangement of atoms. These changes in turn cause the central Al atoms to be less hindered by the surrounding atoms, enhancing the cage-breaking motion and weakening the unusual caged dynamics. In addition, the applied pressure not only increases the diversity of vibrational frequencies but also weakens the difference in atomic vibrational amplitudes, leading to the weakening of the unusual caged dynamics. These findings provide new insights into the caged dynamics under pressure from the perspective of microstructure and vibrational properties.

Understanding the unusual-caged dynamics from the microstructure and interatomic interactions in binary metallic glass-forming liquids

The caged dynamics appears at time shorter than the β-relaxation but longer than the boson peak. Due to the limitations of experimental conditions, the mechanism of caged dynamics is not well studied in metallic glasses. We study a model La65Al35 glass-forming liquid with strong atomic interactions that presents an unusual caged dynamics, and the La65Ni35 GF liquid is also studied to clarify the underlying mechanisms of caged dynamics. There is a sudden drop near 0.1 ps in the partial non-Gaussian parameter of Al atoms, reflecting the development of caging of the Al atoms with time. A similar feature is also found in Ni80P20, Sm80Al20, Pd80Si20, and Y80Mg20 metallic GF liquids. The chemical order, Voronoi polyhedra, and covalent-like bonds are all related to the cage-breaking behavior of the central atoms, in turn regulating the unusual caged dynamics. These findings shed light on the complex relaxation dynamics of GF liquids.

Flexural strength, thermal and dielectric properties of AlN ceramics with BN nanoplatelets addition

The effects of the low-content addition of boron nitride nanoplatelets (BNp) on the microstructure, flexural strength, thermal and dielectric properties of AlN ceramics were studied. X-ray diffraction and microtopography indicated that the platelike BNp phases were detected in the grain boundary, decreasing the grain size of the AlN samples. Flexural strength increased with 0.5 wt% and 1 wt% BNp addition, and such increase was attributed to the smaller grain sizes and the two-dimensional structure bridging mechanism. Comparing the experimental thermal conductivity with the theoretical calculated values, no strong atomic interaction occurred between AlN and BNp, and thermal conductivity slightly decreased with the addition of a suitable amount of BNp. Moreover, the temperature dependence of dielectric spectrum of the samples exhibited a remarkable difference due to the additional polarisation mechanisms caused by the addition of BNp. Overall, suitable addition of BNp can improve flexural strength whilst maintaining the high thermal conductivity and excellent dielectric properties of AlN ceramics.

Analytical results for the superflow of spin-orbit-coupled Bose-Einstein condensates in optical lattices

In this paper, we show that for sufficiently strong atomic interactions, there exist analytical solutions of current-carrying nonlinear Bloch states at the Brillouin zone edge to the model of spin-orbit-coupled Bose-Einstein condensates (BECs) with symmetric spin interaction loaded into optical lattices. These simple but generic exact solutions provide an analytical demonstration of some intriguing properties which have neither an analog in the regular BEC lattice systems nor in the uniform spin-orbit-coupled BEC systems. It is an analytical example for understanding the superfluid and other related properties of the spin-orbit-coupled BEC lattice systems.

Nonlinear absorption in interacting Rydberg electromagnetically-induced-transparency spectra on two-photon resonance

We experimentally investigate the nonlinear transmission spectrum of coherent light fields propagating through a Rydberg EIT medium with strong atomic interactions. In contrast to previous investigations, which have largely focused on resonant control fields, we explore here the full two-dimensional spectral response of the Rydberg gas. Our measurements confirm previously observed spectral features for a vanishing control-field detuning, but also reveal significant differences on two-photon resonance. In particular, we find qualitative deficiencies of mean-field models and rate-equation simulations as well as a third-order nonlinear susceptibility that accounts for pairwise interaction effects at low probe-field intensities in describing the nonlinear probe-field response under EIT conditions. Our results suggest that a more complete understanding of Rydberg EIT and emerging photon interactions requires to go beyond existing simplified models as well as few-photon theories.

Self-Induced Transparency in Warm and Strongly Interacting Rydberg Gases.

We study dispersive optical nonlinearities of short pulses propagating in high number density, warm atomic vapors where the laser resonantly excites atoms to Rydberg P states via a single-photon transition. Three different regimes of the light-atom interaction, dominated by either Doppler broadening, Rydberg atom interactions, or decay due to thermal collisions between ground state and Rydberg atoms, are found. We show that using fast Rabi flopping and strong Rydberg atom interactions, both in the order of gigahertz, can overcome the Doppler effect as well as collisional decay, leading to a sizable dispersive optical nonlinearity on nanosecond timescales. In this regime, self-induced transparency (SIT) emerges when areas of the nanosecond pulse are determined primarily by the Rydberg atom interaction, rather than the area theorem of interaction-free SIT. We identify, both numerically and analytically, the condition to realize Rydberg SIT. Our study contributes to efforts in achieving quantum information processing using glass cell technologies.

Optimized geometric quantum computation with a mesoscopic ensemble of Rydberg atoms

We propose a nonadiabatic non-Abelian geometric quantum operation scheme to realize universal quantum computation with mesoscopic Rydberg atoms. A single control atom entangles a mesoscopic ensemble of target atoms through long-range interactions between Rydberg states. We demonstrate theoretically that both the single qubit and two-qubit quantum gates can achieve high fidelities around or above 99.9% in ideal situations. Besides, to address the experimental issue of Rabi frequency fluctuation (Rabi error) in Rydberg atom and ensemble, we apply the dynamical-invariant-based zero systematic-error sensitivity (ZSS) optimal control theory to the proposed scheme. Our numerical simulations show that the average fidelity could be 99.98% for single ensemble qubit gate and 99.94% for two-qubit gate even when the Rabi frequency of the gate laser acquires 10% fluctuations. We also find that the optimized scheme can also reduce errors caused by higher-order perturbation terms in deriving the Hamiltonian of the ensemble atoms. To address the experimental issue of decoherence error between the ground state and Rydberg levels in Rydberg ensemble, we introduce a dispersive coupling regime between Rydberg and ground levels, based on which the Rydberg state is adiabatically discarded. The numerical simulation demonstrate that the quantum gate is enhanced. By combining strong Rydberg atom interactions, nonadiabatic geometric quantum computation, dynamical invariant and optimal control theory together, our scheme shows a new route to construct fast and robust quantum gates with mesoscopic atomic ensembles. Our study contributes to the ongoing effort in developing quantum information processing with Rydberg atoms trapped in optical lattices or tweezer arrays.

Relaxation, chaos, and thermalization in a three-mode model of a Bose–Einstein condensate

We study the complex quantum dynamics of a system of many interacting atoms in an elongated anharmonic trap. The system is initially in a Bose–Einstein condensed state, well described by Thomas–Fermi profile in the elongated direction and the ground state in the transverse directions. After a sudden quench to a coherent superposition of the ground and lowest energy transverse modes, quantum dynamics starts. We describe this process employing a three-mode many-body model. The experimental realization of this system displays decaying oscillations of the atomic density distribution. While a mean-field description predicts perpetual oscillations of the atomic density distribution, our quantum many-body model exhibits a decay of the oscillations for sufficiently strong atomic interactions. We associate this decay with the fragmentation of the condensate during the evolution. The decay and fragmentation are also linked with the approach of the many-body model to the chaotic regime. The approach to chaos lifts degeneracies and increases the complexity of the eigenstates, enabling the relaxation to equilibrium and the onset of thermalization. We verify that the damping time and quantum signatures of chaos show similar dependences on the interaction strength and on the number of atoms.

Structural, magnetic, and electronic properties of Fe82Si4B10P4 metallic glass

The structural, magnetic, and electronic properties of Fe82Si4B10P4 metallic glass were systemically investigated by theoretical simulations. Strong atomic interaction between Fe and metalloid atoms can be observed, while the direct metalloid-metalloid atomic bonds are rare due to the solute-solute avoidance effect. The calculated value of saturation magnetic flux density (BS) is ~1.65 T, approaching to experimental result, which is contributed by not only the electron exchange between Fe and metalloid atoms, but also the p-d orbital hybridization of Fe atoms. Moreover, Fe atoms with neighboring P atom behaving larger magnetic moments reveals the important role of P element for promoting the BS value. The potential correlation between magnetic behaviors and the local atomic packing in this study sheds some light on the structural origin of the soft magnetic properties and, thereby the theoretical guidance for the development of new soft-magnetic metallic glasses.

Two-body entanglement in a dilute gas of Rydberg atoms

Since the establishment of quantum mechanics, quantum entanglement has become one of the most important realms in quantum physics. On the one hand, it reflects some of the most fascinating features, such as quantum coherence, probability and non-locality and so on. On the other hand, it proves to be an indispensable resource of quantum information processing and quantum computation, which is considered to greatly promote the development of human science and technology. In the past decades, inspired by advances in quantum information theory and quantum physics, people have been searching for suitable systems with great enthusiasm to prepare the robust and manipulable quantum entanglement. Recently, Rydberg atoms have been considered to be a good candidate for many quantum information and quantum computation tasks. Compared with general neutral atoms, Rydberg atoms with large principal quantum number have several advantages in the quantum information and computation service. Firstly, they have finite lifetimes much larger than general neutral atoms, which indicates that the long-time entanglement between Rydberg atoms can be achieved. Secondly, due to the high-excitation level, Rydberg-excitation atoms have long-ranged dipole-dipole interaction much stronger than ground state atoms. This strong atomic interaction leads to the so-called blockade effect: when one atom is excited to Rydberg level, the excitation of the neighboring atoms will be strictly suppressed due to the energy shift induced by the strong atomic interaction. On the contrast, if the energy shift is compensated for by the detuning between the energy levels and the driven laser field, these atoms can be excited with higher probability simultaneously. These effects imply that Rydberg atoms provide an excellent platform for investigating the quantum information and quantum computation process, and many important achievements based on them have been achieved. Encouraged by these researches on entanglement and Rydberg atoms, in this paper, we study the steady-state and transient dynamical properties of two-body entanglement and the Rydberg-excitation properties in a dilute gas of Rydberg atoms, which can be represented by a tetrahedrally arranged interacting four-atom model. By solving numerically the master equation of four atoms involving Rydberg level, we investigate the higher-order Rydberg excitations and bipartite entanglement, which is estimated by concurrence. Our results show that the bipartite entanglement can only achieve its maximal value in the strongest dipole blockade regime rather than anti-blockade one (the high-order Rydberg excitations). Furthermore, the physical essence of quantum entanglement is analyzed theoretically in relevant regimes. Our work can naturally extend to more complicated atomic space structures, and might be treated as a good platform for fulfilling many quantum information tasks by employing the quantum entanglement.

Thermodynamic Properties of Strontium-Lead Alloys Determined by Electromotive Force Measurements

The thermodynamic properties of Sr-Pb alloys were determined by electromotive force (emf) measurements. A Sr(s)|CaF2-SrF2|Sr(in Pb) electrochemical cell was used to measure emf values at 773–1073 K for Sr-Pb alloys at mole fractions xSr = 0.07–0.59. These emf measurements were used to determine thermodynamic properties of Sr-Pb alloys, including activity, partial molar entropy, and partial molar enthalpy. At 873 K, activity values of Sr in Pb were as low as aSr = 1.72 × 10–9 at mole fraction xSr = 0.07, implying strong atomic interactions between Sr and Pb. Phase transition temperatures of Sr-Pb alloys, observed during emf measurements, were corroborated by thermal analysis (0.07 ≤ xSr ≤ 0.34) by differential scanning calorimetry (DSC), and the phase constituents of Sr-Pb alloys (0.07 ≤ xSr ≤ 0.75) were characterized using X-ray diffraction (XRD). Experimentally-determined thermodynamic properties were compared to the assessed thermodynamic properties of the Sr-Pb system, confirming the phase transition temperatures and highlighting discrepancies in solution properties (activity and excess Gibbs energy).

Thermodynamic Properties of Strontium-Lead Alloys Determined By Electromotive Force Measurements

Electrochemical separation is one of the most promising methods for recycling used nuclear fuel, in which uranium is isolated from other fission products using a molten salt electrolyte1. The used fuel is immersed in molten salt electrolyte in an electrochemical cell referred to as an electrorefiner. In an ideal electrorefiner cell the used fuel is dissolved anodically, releasing uranium ions into a ternary chloride salt (LiCl-KCl-10wt%UCl3). The uranium ions are then reduced at an inert cathode, forming uranium metal for reuse in new uranium fuel pellets2. However, in actual electrorefiner systems, uranium is not the only element from the used fuel that is oxidized into the electrolyte. Alkali/alkaline-earth elements, such as cesium, barium, and strontium, are also oxidized because they have lower standard reduction potentials than uranium in the chloride system3. As alkali/alkaline-earth elements accumulate in the electrolyte, they change the physical and chemical properties of the electrolyte due to their short half-lives and high heat densities. The electrolyte is periodically removed from the electrorefiner to maintain the recycling process, thereby generating excessive volumes of nuclear waste. Lichtenstein et al. have demonstrated that alkali/alkaline-earth elements exhibit low thermodynamic activity (6.6 × 10-16 at x Ba = 0.05, 773 K) in liquid metals such as bismuth, implying strong atomic interactions4. These interactions cause a shift in the elements’ reduction potentials and can be leveraged to selectively remove the accumulated elements from the electrolyte by depositing them into liquid metal electrodes. To determine the viability of removing alkali/alkaline-earth elements using liquid metals such as lead, the thermodynamic properties of Sr-Pb alloys were determined by electromotive force (emf) measurements using a solid state electrolyte (binary CaF2-Sr­F­2, 97-3 mol%). Emf values were measured at 723 K-1073 K using a Sr(s)|CaF2-SrF­2|Sr(in Pb) electrochemical cell and were used to determine the thermodynamic properties of Sr-Pb, including activity, partial molar entropy, and partial molar enthalpy for x Sr = 0.05-0.75. At 973 K, activity values of Sr in Pb were as low as 5 × 10-9 at xSr = 0.05, implying strong atomic interactions between Sr and Pb. According to Okamoto et al., the liquid-state solubility of Sr in Pb is approximately 37 mol% at 973 K5. With the high solubility of Sr in Pb in the liquid state, combined with strong Sr-Pb atomic interactions, Pb has demonstrated promise for use as a liquid metal electrode material to remove Sr2+ ions from molten salt electrolytes. [1] Electrometallurgical Techniques for DOE Spent Fuel Treatment: Final Report, National Academy Press Washington, D.C, 2000.[2] Willit, J. L., Miller, W.E., Battles, J.E. Electrorefining of uranium and plutonium – A literature review, J. Nucl. Mater. 195 (3), 229-249 (1992). [3] Roine, A., Outokumpu HSC Chemistry® 5.1; Chemical Reaction and Equilibrium Software with Extensive Thermochemical Database, (2002). [4] Lichtenstein, T., Smith, N.D., Gesualdi, J., Kumar, K., Kim, H. Thermodynamic Properties of Barium-Bismuth Alloys Determined by emf Measurements, Electrochim. Acta. 228, 628-635 (2017). [5] Okamoto, H. Sr-Pb (Strontium-Lead), 2nd ed., ASM International, Materials Park, (1990).

Heralded multiphoton states with coherent spin interactions in waveguide QED

Waveguide QED offers the possibility of generating strong coherent atomic interactions either through appropriate atomic configurations in the dissipative regime or in the bandgap regime. In this work, we show how to harness these interactions in order to herald the generation of highly entangled atomic states, which afterwards can be mapped to generate single mode multi-photonic states with high fidelities. We introduce two protocols for the preparation of the atomic states, we discuss their performance and compare them to previous proposals. In particular, we show that one of them reaches high probability of success for systems with many atoms but low Purcell factors.