bluuebunny/crossref_metadata_2025 huggingface dataset:
Exotic Kondo effect in two one-dimensional spin-1/2 chains coupled to two localized spin-1/2 magnets
Authors: Kuzmenko Igor , Kuzmenko Tetyana , Band Y. B. , Avishai Yshai
Published: December 2024

We study an exotic Kondo effect in a system consisting of two one-dimensional XX Heisenberg ferromagnetic spin-1/2 chains (denoted by α=u,d for up and down chains) coupled to a quantum dot consisting of two localized spin-1/2 magnets. Using the Jordan–Wigner transformation on the Heisenberg Hamiltonian of the two chains, this system can be expressed in terms of non-interacting spinless fermionic quasiparticles. As a result, the Hamiltonian of the whole system is expressed as an Anderson model for spin-1/2 fermions interacting with a spin-1/2 impurity. Thus, we study the scattering of fermionic quasiparticles (propagating along spin chains) by a pair of localized magnetic impurities. At low temperature, the localized spin-1/2 magnets are shielded by the chain “spins” via the Kondo effect. We calculate the Kondo temperature TK and derive the temperature dependence of the entropy, the specific heat and the “magnetic susceptibility” of the dot for T≫TK. Our results can be generalized to the case of antiferromagnetic XX chains.
New regime of the Coulomb blockade in quantum dots
Authors: McArdle G. , Davies R. , Lerner I. V. , Yurkevich I. V.
Published: December 2024

We consider how the absence of thermalization affects the classical Coulomb blockade regime in quantum dots. By solving the quantum kinetic equation in the experimentally accessible regime when the dot has two relevant occupation states, we calculate the current–voltage characteristics for arbitrary coupling to the leads. If the couplings are strongly asymmetric, the Coulomb staircase is practically reduced to the first step, which is independent of the charging energy, when the Fermi energy is comparatively small, while the standard thermalized results are recovered in the opposite case. When the couplings are of the same order, the absence of thermalization has a new, striking signature—a robust additional peak in the differential conductance.
About the attraction of hot particles in a cold bath
Authors: Grosberg Alexander Y.
Published: December 2024

Motivated by questions in biological physics, we consider a model in which different Brownian particles interact with different thermostats. Computer simulations show that hot particles (i.e., interacting with the hot bath) attract each other when placed in an environment of colder particles (i.e., interacting with the cold thermostat). This paper presents a simple calculation that sheds light on the physical nature of this attraction.
A toy model for two-dimensional spin-fluctuation-induced unconventional superconductivity
Authors: Cao Tu M. , Mazin Igor I.
Published: December 2024

Superconductivity had been one of the most enigmatic phenomena in condensed matter physics, puzzling the best theorists for 45 years, since the original discovery by Kamerlingh-Onnes in 1911 till the final solution by Bardeen, Cooper, and Schrieffer (BCS) in 1957. The original BCS proposal assumed the highest-symmetry form for the superconducting order parameter Δ, namely, a constant, and a uniform pairing interaction due to attractive mediation of ionic vibration. While it was rather soon realized that generalizations onto k-dependent order parameters and anisotropic pairing interaction was straightforward, only thirty years later, upon the discovery of high-temperature superconductivity in cuprates, high-order angular dependence of Δ and repulsive interaction, mediated by spin fluctuations or Coulomb repulsion brought such “unconventional” into the spotlight. In 2008 yet another such system was discovered, and eventually the idea of repulsion-mediated unconventional superconductivity was generally accepted. Apart from the two specific systems mentioned above, a large number of various specific implementations of this idea have been proposed, and it is becoming increasingly clear that it is worth studying mathematically how unconventional superconductivity emerges, and with what properties, for a simple, but sufficiently general theoretical model. In our project, we study systematically unconventional superconductivity in an isotropic two-dimensional model system of electrons, subjected to repulsive interactions of a simple, but physically motivated form: a delta function peaked at a particular momentum (from 0 to twice the Fermi momentum), or Gaussian of varying widths.
From disorder and metamaterials to chirality
Authors: Kivshar Yuri
Published: December 2024

Sergey Gredeskul was an outstanding theoretical physicist who visited us in Australia many times, and he published many papers with the members of our Nonlinear Physics Center in Canberra and many other colleagues. This short article brings some memories about our collaborative work, and also it reports on the recent developments with chiral metasurfaces, the topic that Sergey and I planned to work on together a long time ago.
On the relation between the velocity- and position-Verlet integrators
Authors: Ni Liyan , Hu Zhonghan
Published: December 2024

The difference and similarity between the velocity- and position-Verlet integrators are discussed from the viewpoint of their Hamiltonian representations for both linear and nonlinear systems. For a harmonic oscillator, the exact Hamiltonians reveal that positional trajectories generated by the two integrators follow an identical second-order differential equation and thus can be matched by adjusting initial conditions. In contrast, the series expansion of the Hamiltonians for the nonlinear discrete dynamics clearly indicates that the two integrators differ fundamentally. These analytical results are confirmed by simple numerical simulations of harmonic and anharmonic oscillators.
Realizing multi-level phase-change storage by monatomic antimony
Authors: Yin Tianhao , Gu Jierong , Wang Guoxiang , Gu Chenjie , Chen Bin , Shen Xiang , Chen Yimin
Published: December 2024

With the growing need for extensive data storage, enhancing the storage density of nonvolatile memory technologies presents a significant challenge for commercial applications. This study explores the use of monatomic antimony (Sb) in multi-level phase-change storage, leveraging its thickness-dependent crystallization behavior. We optimized nanoscale Sb films capped with a 4-nm SiO2 layer, which exhibit excellent amorphous thermal stability. The crystallization temperature ranges from 165 to 245 °C as the film thickness decreases from 5 to 3 nm. These optimized films were then assembled into a multilayer structure to achieve multi-level phase-change storage. A typical multilayer film consisting of three Sb layers was fabricated as phase-change random access memory (PCRAM), demonstrating four distinct resistance states with a large on/off ratio (∼102) and significant variation in operation voltage (∼0.5 V). This rapid, reversible, and low-energy multi-level storage was achieved using an electrical pulse as short as 20 ns at low voltages of 1.0, 2.1, 3.0, and 3.6 V for the first, second, and third SET operation, and RESET operation, respectively. The multi-level storage capability, enabled by segregation-free Sb with enhanced thermal stability through nano-confinement effects, offers a promising pathway toward high-density PCRAM suitable for large-scale neuromorphic computing.
A capacitive tactile force sensor with mutual fringe effect and parallel plate design for robot assisted surgery
Authors: Arshad Adeel , Saleem Muhammad Mubasher , Javaid Faraz , Jabbar Hamid
Published: December 2024

This paper presents a unique design of a single-axis tactile force sensor by a mutual parallel plate and fringing effect of an electric field that is generated between stationary patterned electrodes in the sensor. The proposed sensor can measure the normal and shear forces with high sensitivity and linear response. The capacitive tactile sensor is fabricated by low-cost rapid prototyping techniques using conductive ink for electrode printing that is printed on a polyethylene terephthalate sheet by an inkjet printer. Ecoflex 00-30 and silicone rubber RTV-528 are used as the dielectric medium and dome for force application. A finite element method analysis is performed for deciding the dimensions of the sensor's stationary electrodes. The force measurement ranges of the sensor for the normal and shear axis are 4 N and 2 N, respectively. The proposed tactile sensor shows a highly linear response, which makes it a suitable match for force feedback in robotic surgery.
Spin Hall magnetic field sensing device using topological insulator
Authors: Liu Min , Ruixian Zhang , Le Quang , York Brian , Hwang Cherngye , Liu Xiaoyong , Gribelyuk Michael , Xu Xiaoyu , Le Son , Maeda Maki , Fan Tuo , Tao Yu , Takano Hisashi , Hai Pham Nam
Published: December 2024

The “direct” spin Hall (DSH) effect has been intensively studied to manipulate the magnetic state in spin–orbit torque magnetic random access memory. Meanwhile, its reciprocal phenomenon, known as the “inverse” spin Hall (ISH) effect, has been studied as a method to read the magnetic state of a magnetic element in a magnetic read head sensor and magnetoelectric spin–orbit logic device. This work studies a magnetic field sensing device structure in which the DSH effect is used for reading the magnetic state in a ferromagnetic (FM)/topological insulator (TI) heterostructure. We found that while the output of our DSH sensing device is consistent with that based on the ISH effect, the spin Hall angle calculated from its magnitude is colossal (θSH ∼ 164) and significantly higher than that (θSH ∼ 3.5) obtained from the second harmonic measurement. Our findings show that the giant DSH and ISH effects in TI-based heterostructures are useful for realizing next-generation magnetic read head device and have important implications for engineering topological quantum materials with high spin Hall performance.
Cogwheel phase cycling in population-detected optical coherent multidimensional spectroscopy
Authors: Jayachandran Ajay , Mueller Stefan , Brixner Tobias
Published: December 2024

An integral procedure in every coherent multidimensional spectroscopy experiment is to suppress undesired background signals. For that purpose, one can employ a particular phase-matching geometry or phase cycling, a procedure that was adapted from nuclear magnetic resonance (NMR) spectroscopy. In optical multidimensional spectroscopy, phase cycling has been usually carried out in a “nested” fashion, where pulse phases are incremented sequentially with linearly spaced increments. Another phase-cycling approach that was developed for NMR spectroscopy is “cogwheel phase cycling,” where all pulse phases are varied simultaneously in increments defined by so-called “winding numbers.” Here we explore the concept of cogwheel phase cycling in the context of population-based coherent multidimensional spectroscopy. We derive selection rules for resolving and extracting fourth-order and higher-order nonlinear signals by cogwheel phase cycling and describe how to perform a numerical search for the winding numbers for various population-detected 2D spectroscopy experiments. We also provide an expression for a numerical search for nested phase-cycling schemes and predict the most economical schemes of both approaches for a wide range of nonlinear signals. The signal selectivity of the technique is demonstrated experimentally by acquiring rephasing and nonrephasing fourth-order signals of a laser dye by both phase-cycling approaches. We find that individual nonlinear signal contributions are, in most cases, captured with fewer steps by cogwheel phase cycling compared to nested phase cycling.
Elucidating and contrasting the mechanisms for Mg and Ca sulfate ion-pair formation with multi-level embedded quantum mechanics/molecular dynamics simulations
Authors: Boyn Jan-Niklas , Carter Emily A.
Published: December 2024

Solutions and minerals containing sulfate (SO42−), and Ca2+ and Mg2+ cations, are ubiquitous throughout the lithosphere and are significant components of seawater, thus presenting a prototypical system for the study of strong electrolytes and crystal nucleation mechanisms. However, despite their relative abundance, key questions remain unanswered about the most fundamental atomic-level steps of their mineralization pathways and aqueous dynamics. Here, we carry out enhanced sampling multi-level molecular dynamics (MD) embedded correlated wavefunction theory simulations to elucidate ion-pairing mechanisms for Mg–SO4 and Ca–SO4 in concentrated aqueous solution, accurately capturing effects arising from both structural dynamics and electron exchange–correlation. We predict contact-ion-pair formation to be barrierless and highly exoergic for Ca–SO4, in agreement with its minimal solubility, whereas for Mg–SO4, solvent-shared and contact ion pairs have similar free energies, qualitatively consistent with its higher solubility. Finally, we demonstrate that brief high-temperature pre-equilibration may be utilized to accelerate convergence of free energies in blue-moon-ensemble enhanced-sampling MD.
Analyzing the water stability mechanism in O-type NaLi0.33Mn0.67O2 as a cathode material for sodium-ion batteries
Authors: Xu Bo , Qin Wenjing , Sun Baozhen , Wu Musheng , Liu Sanqiu
Published: December 2024

The moisture-induced instability of the sodium-layered transition metal oxides (NaxTMO2) presents a significant challenge in developing electrode materials for sodium-ion batteries (SIBs). Herein, via first-principles calculations, we investigate the impact of Li substitution on the water stability of O-type NaLi0.33Mn0.67O2 (NLMO). In particular, the processes of H2O decomposition, Na+/H+ exchange reaction, and hydrogen (H) diffusion on NLMO (101), are specifically compared with those on NMO (101). The results demonstrate that H2O can decompose into O and H species at the Mn–Mn bridge site, but into OH and O species at the Na–Na bridge site, suggesting H2O is unstable on both surfaces. Thereafter, Na+/H+ exchange reaction becomes more difficult on NLMO (101), with the values of −2.73/−2.25 eV and −3.45/−2.82 eV in P1/P2 sites for NLMO (101) and NMO (101). Meanwhile, H diffusion on NLMO (101) is also more difficult due to hydrogen resistance from the subsurface to the bulk. The corresponding barriers are 2.17 and 1.63 eV. However for NMO (101), H can penetrate from the surface to the subsurface and continue to the bulk, with the lowest barrier of 0.61 eV (“Path III-12”) and 0.83 eV (“Path I-23”), respectively. The Columbic interaction between H and metal (Li, Mn, and Na) atoms plays a key role in hydrogen resistance. Notably, Li doping can increase the difficulties in the Na+/H+ exchange reaction and H diffusion on NLMO (101). For this reason, NLMO shows stronger water stability compared to NMO. The in-depth understanding of the water stability mechanism of NLMO can facilitate the future development of high-stable cathodes for SIBs.
Excited states from GW/BSE and Hartree–Fock theory: Effects of polarizability and transition type on accuracy of excited state energies
Authors: Waide David T. , Patterson Charles H.
Published: December 2024

GW and Bethe–Salpeter equation (BSE) methods are used to calculate energies of excited states of organic molecules in the Quest-3 database [Loos et al., J. Chem. Theory Comput. 16, 1711 (2020)]. The self-energy in the GW approximation is conventionally calculated using the RPA polarizability. Inclusion of a screened electron–hole interaction in the polarizability was recently shown to improve predictions of experimental ionization energies in organic molecules [C. H. Patterson, J. Chem. Theory Comput. 20, 7479 (2024)]. Self-energies from RPA or screened time-dependent Hartree–Fock (TDHF) polarizabilities in the GW/BSE method are used to calculate 141 singlet excited states in Quest-3. Theoretical best estimate excited state energies from the CC3 coupled cluster method and aug-cc-pVTZ basis sets are used to benchmark GW/BSE and CIS calculations using the same molecular geometries and basis sets. Differences between GW/BSE or CIS excited state energies and best estimate values show that there are systematic variations in the accuracies of excited state energies classified as ππ*, nπ*, πR (Rydberg), or nR character. The origin of these variations is the accuracy of self-energies of states of nonbonding vs π bonding character. In particular, N or O lone pair states require large self-energy corrections owing to strong orbital relaxation in the localized hole state, while π states have smaller corrections. Self-energies from a screened TDHF vs RPA polarizability are typically over(under)estimated for nonbonding states, leading to under(over)estimation of energies of excited states of nπ* or nR character.
Effect of simple shear on knotted polymer coils and globules
Authors: Milchev Andrey , Schmitt Maurice P. , Virnau Peter
Published: December 2024

We explore the effect of Couette flow on knotted linear polymer chains with extensive molecular dynamics simulations. Hydrodynamic interactions are accounted for using multi-particle collision dynamics. The polymer chain, originally containing a simple trefoil knot at rest, is described by a coarse-grained bead-spring model in a coil or globular state. We demonstrate that under shear existing loosely localized knots in polymer coils typically tighten to several segments beyond a certain shear rate threshold. At large shear rates, the polymer undergoes a tumbling-like motion during which knot sizes can fluctuate. In contrast, sheared knotted globules unwind into a convoluted pearl-necklace structure of sub-globules that folds back onto itself and in which knot types change over time.
Insights of phosphor charging upon exposure to intense illumination
Authors: Sun Quan , Luan Yuning , Shi Tingxing , Zhu Yaqi , Liu Feng , Zhang Liangliang , Zhang Jiahua , Wang Xiao-jun , Liu Yichun
Published: December 2024

Storage phosphors, known for their delayed emission after charging, have shown great potential for applications in radiation detection, bio-imaging, and medical diagnosis. Despite their promise, the underlying mechanisms governing their charging behavior have not been sufficiently investigated. In this Letter, we elucidate the response of storage phosphors, focusing on the Y3Sc2Ga3O12:Pr3+ composition, when subjected to intense illumination. Our findings reveal that upon exposure to 266 nm ultraviolet or 450 nm blue lasers, the phosphor efficiently captures excitation energy through direct photoionization or upconversion charging (UCC), leading to subsequent trap filling. Thermoluminescence measurements, incorporating variations in irradiation power and dose, confirm that UCC enables an impressive fast charging time of 0.01 s. The unique two-step ionization and nonlinear charging characteristics of UCC are visually demonstrated using a portable laser engraver. Furthermore, we illustrate the versatility of UCC across different phosphor systems, highlighting its potential for advanced information storage applications. This research significantly advances the understanding of phosphor charging dynamics, paving the way for future innovations in luminescent materials.
Robust cavitation-based pumping into a capillary
Authors: Heidary Z. , Fan Y. , Mojra A. , Ohl C. D.
Published: December 2024

Cavitation bubbles collapsing near boundaries create liquid flow through their center of mass movement, the formation of liquid jets, and long living vorticities. Here, we demonstrate robust pumping of the liquid with a compact and simple geometry, the open end of a thin-walled circular capillary tube filled with liquid. We study the dynamics of the cavitation bubbles and report on the resultant microjet formation through experiments and simulations. In the experiments, the dynamics of laser-induced cavitation bubbles are captured with high-speed microscopy. Simulations show excellent agreement with the experiments. The jet flow pumps liquid flow toward the capillary opening. The simulation reveals that, in the current study range, both the non-dimensional inner diameter of the capillary and the non-dimensional stand-off distance show influences on the jet width, and only the non-dimensional stand-off distance affects the maximum jet velocities. The results demonstrate that the confinement of the bubble within the capillary alters the anisotropic pressure field around the bubble, leading to a more mild collapse.
A nonequilibrium kinetic model of high-resolution vibrational energy transfer in RDX from selective IR excitation
Authors: Liu Zhiyu , Batyrev Iskander G. , Byrd Edward F. C. , Chung Peter W.
Published: December 2024

In this paper, we develop a model based on a second quantization—with anharmonic phonon scattering and the phonon Boltzmann transport equation—to study precise high-resolution nonequilibrium vibrational energy transfer (VET) under selective phonon excitation in cyclotrimethylene trinitramine. We simulate mid-infrared pump–probe spectroscopy and observe a prompt appearance (<1 ps) of broad-spectrum intensity, which agrees well with experimental data in the literature. The selective excitation of phonons at different frequencies reveals distinct VET pathways and the kinetic evolution of mode occupations as the system reaches a new equilibrium temperature. Three types of transition mechanisms are found to play outsized roles in terms of the amount of energy transferred and the transfer rate: (1) vibrational modes close to the excited frequencies typically respond faster and reach higher temperatures regardless of the excitation frequency; (2) the overtone pathway connecting the modes near 550 and 1150 cm−1 is an important bridge between far- and mid-IR; and (3) fast aggregation of energy at 2800 cm−1 mediates transfer to/from high frequencies through a second overtone pathway involving modes near 1400 cm−1. In addition, by monitoring the temperature of the N–N/N–O stretching modes, strong coupling between those modes and the C–H stretching modes is found. The coupling likely draws the vibrational modes close to both the proton transfer transition state for HONO elimination and the N–N stretching for bond cleavage. The high-resolution understanding of the nonequilibrium kinetics of phonons provides important insight into the energy transfer and initiation mechanisms of molecular solids due to external stimuli.
Abnormal widening of the domain touching the electrode during in-plane local switching in lithium niobate
Authors: Turygin A. P. , Alikin D. O. , Kosobokov M. S. , Akhmatkhanov A. R. , Shur V. Ya.
Published: December 2024

The qualitatively different domain evolution scenarios for different polarities of applied voltage pulses have been studied. For positive pulse, the domain demonstrates only slight width increase during further switching and high stability during subsequent domain imaging. For negative pulse, faster domain widening at the electrode as compared to the domain base leads to change in the type of charged domain wall (CDW) from tail-to-tail (t2t) to head-to-head (h2h) as well as formation of the domain teeth at CDW and an array of wedge-like domains. Additional domain imaging leads to reconstruction of the wedge-like domain with t2t CDW. It was demonstrated by numerical simulation that the switching field is above the threshold for step generation in wide region along the electrode. This field stimulates the formation of above-mentioned domain structure. The absence of this effect for positive pulse has been attributed to the huge difference in conductivity of t2t and h2h CDWs. The current along conductive h2h CDW after domain touching results in decrease in the tip bias due to voltage drop on the series resistance. The stability of the domains growing from the tip was attributed to effective screening of depolarization field by the injected charge. The ineffective screening at the electrode due to absence of charge injection stimulates domain backswitching. The obtained knowledge is useful for further development of domain engineering methods in thin films for the fabrication of periodically poled waveguides.
Charge transport mechanism in [GeOx](z)[SiO2](1-z) based MIS structures
Authors: Yushkov I. D. , Gismatulin A. A. , Prosvirin I. P. , Kamaev G. N. , Marin D. V. , Vergnat M. , Volodin V. A.
Published: December 2024

The mechanisms of conductivity in metal–insulator–semiconductor (MIS) structures based on [GeOx](z)[SiO2](1-z) films (0.25 ≤ z ≤ 1) fabricated by co-evaporation of germanium oxide and silicon oxide powders in vacuum and deposition on a p+-type silicon substrate are studied. Indium tin oxide deposited by magnetron method is used as the top electrode. According to IR spectroscopy, Ge–O, Si–O, and Ge–O–Si bonds are detected in the films, while no features related to the presence of germanium clusters are found in the Raman spectra. The current–voltage characteristics (I–V curves) are measured at different temperatures and analyzed by applying the eight most common models of charge transport in MIS structures. It is found that the experimental I–V curves are most accurately approximated in the space charge limited current model, and the parameters of the charge traps are determined within this model.
Dispersal induced catastrophic bifurcations, Arnold tongues, shrimp structures, and stock patterns in an ecological system
Authors: Rajni  , Ghosh Bapan
Published: December 2024

This paper presents a comprehensive analysis of a discrete-time predator–prey model within a homogeneous two-patch environment, incorporating both prey and predator dispersal. We consider a logistic growth for both prey and predator species, and the predation process is based on the Holling type-II functional response in the isolated patches. We explore the existence of multiple coexisting equilibria and establish their stability conditions. By independently varying the prey and predator dispersal rates, we discover a sequence of phenomena including bifurcations, quasiperiodicity, and chaos. In addition, we observe a 10-period orbit, each point of the periodic orbit gives birth to a closed invariant curve. Such large number of closed invariant curves are generally not reported in spatially coupled population models. The system exhibits both catastrophic (non-smooth) jumps and smooth transitions in the dynamics whenever a bifurcation occurs. Commonly, dispersal can only destabilize the coexisting equilibrium. However, we found the stabilization of the coexisting equilibrium, which is a rare occurrence. Furthermore, a two-parameter space analysis reveals intricate dynamics when both dispersal rates are varied simultaneously, showcasing complex phenomena and the emergence of organized periodic regimes such as Arnold tongues and shrimp structures. We also investigate the stock pattern of both species with respect to the dispersal. This study enhances the understanding of predator–prey interactions in spatially homogeneous environments, illuminating their intricate and dynamic nature.
On the compatibility of the Madrid-2019 force field for electrolytes with the TIP4P/Ice water model
Authors: Blazquez Samuel , Sedano Lucia F. , Vega Carlos
Published: December 2024

The Madrid-2019 force field was recently developed to perform simulations of electrolytes in water. The model was specifically parameterized for TIP4P/2005 water and uses scaled charges for the ions. In this work, we test the compatibility of the Madrid-2019 force field with another water model: TIP4P/Ice. We shall denote this combination as Madrid-2019(TIP4P/Ice) force field. The key idea of this combination is to keep the ion–ion (Madrid-2019) and water–water (TIP4P/Ice) interactions unaltered with respect to the original models and taking the Lennard-Jones parameters for the ion–water interactions from the Madrid-2019 force field. By implementing this approach, we have maintained a reasonably good performance of the model regarding the densities and structural features of aqueous solutions, albeit yielding a moderately higher viscosity than the original model. However, the standout achievement of this new combination lies in its effective reproduction of the absolute values of the freezing temperatures of a number of ionic aqueous solutions, which could also be useful when studying hydrate formation from a two-phase system containing an aqueous solution in contact with a gas.
Crystallographic symmetry increasing in the pressure-induced phase transition of the hydrogen-bonded organic crystal 1-methylhydantoin
Authors: Zhang Zhiheng , Zhang Xiaoxiang , Duan Ruijie , Zhao Yichen , Jia Wenpeng , Liu Yongli , Liu Wengang , Dai Yuxiang , He Ben-Guo
Published: December 2024

In situ high-pressure Raman spectroscopy and synchrotron angular dispersive x-ray diffraction techniques, combined with first-principles calculations, have been performed to investigate the 1-methylhydantoin (C4H6N2O2, 1-MH) molecular crystal. High-pressure experiments have shown that phase I (monoclinic system) begins to transform into phase II (orthorhombic system) at pressures above 4.0 GPa, and the transformation range is from 4.0 to 14.2 GPa. It is proposed that the mechanism of phase transition is the interlayer contraction and rearrangement of the hydrogen-bonding network due to the enhanced strong hydrogen-bonded interactions at high pressures. This study provides some theoretical basis for this rare pressure-induced phase transition from low symmetry to high symmetry in organic supramolecular polymorphism.
Evolutionary dynamics in spatial public goods games with environmental feedbacks
Authors: Ding Rui , Wang Xianjia , Zhao Jinhua , Gu Cuiling , Chen Wenman
Published: December 2024

Collective actions aimed at achieving goals such as resource sustainability and environmental protection often face conflicting interests between individuals and groups. These social dilemmas can be modeled using public goods games and collective risk dilemmas. However, in reality, multiple generations share a common pool of resources, leading to high costs for today's overexploitation that impacts future generations' welfare. This delayed effect creates a multigenerational conflict. To address this, we develop a coupled social-ecological coevolutionary model by establishing a relationship between individual payoffs and regional environmental quality. Our goal is to study how cooperative behaviors spread in a public goods game with environmental feedback and to identify the factors influencing this spread. We achieve this by examining the mechanisms behind certain phases and phase transitions, monitoring the spatial distribution of strategies, and assessing the environmental quality of all regions. Our findings reveal some counterintuitive results. For instance, despite cooperators' ability to enhance the environment, the overall level of cooperation in the system sometimes decreases. This is linked to cooperative clusters being invaded by defectors within the clusters' cracks. Additionally, the destructive power of defection and the cost of cooperation have more complex effects on the system.
Effective radius of a contact diffusion-controlled reaction between small solutes and a polymer chain
Authors: Borovkov V. I. , Chetverikov A. O.
Published: December 2024

The aim of this study was to develop a formula for estimating the effective radius of a diffusion-controlled irreversible contact reaction between diffusing solutes and a nonlinear immobile polymer molecule. Analytical expressions for the reaction radius were obtained that took into account averaging over conformations for chains with arbitrary segment-to-segment angles and distributions of dihedral angles. A comparison of the analytical results with the results of computer stochastic modeling of the reaction showed good agreement over a wide range of parameters. Based on an analysis of these expressions, parameter ranges were established in which it was possible to use either the linear chain or Gaussian coil approximation to describe the reaction kinetics. A comparison of several distributions over chain lengths showed that, as a first approximation, the radius of reaction can be estimated as that for a chain corresponding to the number-averaged molecular weight. Results of earlier experimental studies on charge scavenging by polymer molecules have been explained.
Magnetization reversal of perpendicular magnetic anisotropy multilayers on polymeric substrates for flexible spintronics applications
Authors: Bevan R. S. , Chhatoi R. , Mallick S. , Cafolla C. , Nicholson B. , Bedanta S. , Atkinson D.
Published: December 2024

Earlier demonstrations of spintronic functionality on flexible substrates have highlighted the potential for spintronics in flexible electronics applications. However, for device applications, the relationship between global magnetization reversal, as measured by hysteresis, and the local reversal processes of nucleation and growth of magnetic domains need to be understood for magnetic systems on flexible substrates. This study compares the local magnetization reversal behavior of perpendicularly magnetized Pt/CoFeB/Pt and Pt/Co/Pt on rigid and flexible polymeric substrates using magneto-optical Kerr effect magnetometry and microscopy. It is shown that while the magnetic hysteresis is comparable, the local details of the nucleation and field driven reversal are quite different and are attributed to the greater variability of the surface structures of the polymeric substrates, which has implications for consistency in device performance.
Reservoir computing and advanced synaptic plasticity of sputter-deposited ZnO memristors with controllable threshold and nonvolatile switching behavior
Authors: Ismail Muhammad , Seo Euncho , Rasheed Maria , Park Yongjin , Mahata Chandreswar , Kim Sungjun
Published: December 2024

This study presents an ITO/ZnO/ITO/Si memristor fabricated via reactive sputtering for use in advanced analog synaptic plasticity and reservoir computing (RC) systems. The proposed device exhibited stable threshold and nonvolatile switching characteristics by effectively controlling the current compliance (ICC) limit. Multilevel data storage was achieved through controlled multistate switching via reset-stop voltage and ICC. X-ray diffraction analysis confirmed the formation of a polycrystalline ZnO film with a 12:8 oxygen-to-argon ratio, which facilitated the generation of oxygen-vacancy conductive filaments. The memristor effectively replicated key synaptic characteristics such as long-term potentiation, long-term depression, spike-amplitude/width-dependent plasticity, spike-rate-dependent plasticity, and the transition from short-term to long-term memory. The RC system processed binary 4-bit codes and recognized different digits, achieving 98.84% accuracy in handwritten digit recognition using a convolutional neural network simulation, highlighting its potential for efficient image processing applications.
Magnon and electromagnon excitations in Dy0.9Nd0.1FeO3 single crystals tuned with temperature and magnetic field
Authors: Fu Zhichao , Chen Junyu , Shang Jiamin , Lin Xian , Suo Peng , Sun Kaiwen , Wang Chen , Li Qixin , Luo JianLin , Wang Xinbo , Wu Anhua , Ma Guohong
Published: December 2024

Magnon and electromagnon excitations in RFeO3 (where R is a rare-earth element) are associated with the orderings of Fe and R ions, respectively, both of which strongly depend on temperature and applied magnetic field. Herein, by employing the magnetic and electric components of terahertz radiation, we have investigated the temperature and magnetic field dependent magnon and electromagnon excitations in Dy0.9Nd0.1FeO3 single crystals. Our results demonstrate that a small fraction of Nd-substituted Dy ion in Dy1−xNdxFeO3 (with x = 0.1) single crystals shows negligible influence on quasi-ferromagnetic (q-FM) and quasi-antiferromagnetic (q-AFM) modes when the temperature is above TNR, the ordering temperature of rare-earth ions. By contrast, introduction of 10% doping concentration of Nd element leads to changes in exchange interaction of rare-earth ions, consequently altering the frequencies of the electromagnon. Applying magnetic field along different crystal axes can tune the frequency of both q-FM and q-AFM modes and even trigger Fe3+-based spin reorientation phase transition. Furthermore, application of magnetic field can suppress the ordering of rare-earth ions and electromagnon excitation. We anticipate that our findings can advance the understanding of magnetoelectric coupling mechanisms and pave the way for the development of advanced multiferroic materials with tailored properties.
Anomalous excitation wavelength dependent photoluminescence of Sb3+/Bi3+ co-doped double perovskites
Authors: Shi Jia-Jian , Zhu Yi-Lin , Gu Shi-Ying , Shi Chuan-Guo
Published: December 2024

Lead-free double perovskites have recently attracted lots of research interest due to their enhanced structural stability and decreased toxicity compared to lead-halide perovskites. However, origins of the dual emissions observed in photoluminescence (PL) are still controversial. Herein, PL properties of Sb/Bi co-doped Cs2NaInCl6 microcrystals are investigated. When the excitation wavelength is about 320–360 nm, the emission peak mainly locates at 450 nm. While excited at 250 nm, the emission peak reversely increases to ∼580 nm. According to Stokes shift, bandwidth, PL excitation spectra, PL lifetime, and temperature dependent PL, the 450 and 580 nm emissions are attributed to recombination of free exciton (FE) and self-trapped exciton (STE), respectively. Only when the excitation photon energy is large enough to generate lattice distortion and create excitons simultaneously does the STE form, exhibiting emission at 580 nm. As excitation wavelength increases, the photon energy becomes insufficient for the formation of the STE but is able to create FEs. Thus, the emission is dominated by FE recombination. Therefore, the excitation wavelength dependent PL peak position is observed. Moreover, we demonstrate an anti-counterfeiting pattern with excitation wavelength dependent color, which cannot be imitated by other luminescent materials, implying an improved security.
Gas storage in low-permeability rocks
Authors: Xu Jiwei , Gong Yu'an , Wang Meng , Liu Rentai , Liu Yankai
Published: December 2024

Low-permeability, dense sandstone formations are ideal for underground gas storage in compressed air energy storage. To examine the gas permeability of fine sandstone under high pressure, a self-developed triaxial high-pressure gas permeameter was used for experiments under varying confining and axial pressures. The study identified unsteady seepage variations and stress dependence in porous media represented by fine sandstone and developed a gas leakage model. Results indicate that the seepage process includes rapid, slow, and cessation stages. Fine sandstone shows excellent storage capacity, with a daily leakage rate of 0.0463%, below required thresholds. This study guides high-pressure gas permeability theories and modeling.
The subarctic ancient Lake El’gygytgyn harbours the world’s northernmost ‘limnostygon communityʼ and reshuffles crangonyctoid systematics (Crustacea, Amphipoda)
Authors: Copilaş-Ciocianu Denis , Prokin Alexander , Esin Evgeny , Shkil Fedor , Zlenko Dmitriy , Markevich Grigorii , Sidorov Dmitry
Published: December 2024

The northward distribution limit of groundwater fauna is generally dictated by the extent of glacial ice sheets during the Pleistocene. However, some taxa can be found far above this limit, sometimes on isolated oceanic islands, implying long-term survival in subglacial subterranean refugia. Here we report a peculiar assemblage comprising two new depigmented and blind (stygomorphic) amphipods from the subarctic ancient lake El’gygytgyn (northern Far East): Palearcticarellus hyperboreus sp. nov. and Pseudocrangonyx elgygytgynicus sp. nov. Molecular phylogenetic analyses based on five markers confirm their affinity to Crangonyctidae and Pseudocrangonyctidae, respectively. Fossil-calibrated molecular dating indicates that the ages of both species predate the onset of Pleistocene glaciations by at least an order of magnitude. Although both species are clearly adapted for subterranean life and are related to groundwater taxa, they are only known from the lake waters (5–170-m depth). Despite being nested within Pseudocrangonyctidae, P. elgygytgynicus has an atypical third uropod that preserves a vestigial inner ramus, a trait characteristic to the monotypic sister family Crymostygidae. Given that this character was the main distinguishing feature between the two families, we propose merging Crymostygidae with Pseudocrangonyctidae. Our findings represent the world’s northernmost record of stygomorphic amphipods, emphasising their relictual biogeography and the importance of Lake El’gygytgyn as a long-term, high latitude refugium for ancient pre-glacial fauna. ZooBank: urn:lsid:zoobank.org:pub:3A51D1F8-E65D-4A3A-B663-D5C40272E68B
The distribution and significance of stingray feeding pits in Quandamooka (Moreton Bay), Australia
Authors: Giaroli Max L. , Byrne Ilha , Gilby Ben L. , Taylor Matthew , Chargulaf Craig A. , Tibbetts Ian R.
Published: December 2024

Context Quandamooka (Moreton Bay) is a large, subtropical, urban, Ramsar-listed marine park in which stingray feeding pits (SRFPs) provide nursery habitat for commercially important nekton. Aims Nearmap aerial images were used to assess the distribution and abundance of SRFPs and their relationship to shore characteristics around Quandamooka’s perimeter. Methods SRFPs were surveyed using 25-m2 quadrats overlain on aerial images at 65 sites on low-energy tidal flats around the perimeter of Quandamooka, and a polygon encompassing the region with the highest SRFP densities was used to make a preliminary assessment of its potential contribution to whiting and prawn fisheries. Key results SRFPs were present at 63 of the 65 sites surveyed, with habitat type in the high shore (especially mangroves v. seawalls) being the most important spatial driver of SRFP density. Conclusions Eastern Quandamooka sites held more SRFPs and may therefore be an important nursery habitat, holding an estimated 600,000 individuals of postlarval whiting (genus Sillago) and 8 million postlarval penaeid prawns. Implications Given the potentially important role of SRFPs for fisheries, especially those adjacent to mangroves, they should be considered a specific habitat type in future marine park zoning plans and managers should ensure the ongoing protection of stingrays.
Early human collective practices and symbolism in the Early Upper Paleolithic of Southwest Asia
Authors: Barzilai Omry , Marder Ofer , Tejero José-Miguel , Ayalon Avner , Bar-Matthews Miryam , Abulafia Talia , Lavi Ron , Goder-Goldberger Mae , Shemer Maayan , Edeltin Lotan , Wiegmann Alexander , Frumkin Amos , Karasik Avshalom , Yasur Gal , Yeshurun Reuven , Zohar Irit , Berna Francesco , Hans Mark , Goldberg Jerold S. , McDermott Yvonne , Spurlock Linda , Pokhojaev Ariel , Habashi Waseem , May Hila , Sarig Rachel , Hershkovitz Israel
Published: December 2024

Identifying communal rituals in the Paleolithic is of scientific importance, as it reflects the expression of collective identity and the maintenance of group cohesion. This study provides evidence indicating the practice of deep cave collective rituals in the Levant during the Early Upper Paleolithic (EUP) period. It is demonstrated that these gatherings occurred within a distinct ritual compound and were centered around an engraved object in the deepest part of Manot Cave, a pivotal EUP site in southwest Asia. The ritual compound, segregated from the living areas, encompasses a large gallery partitioned by a cluster of remarkable speleothems. Within this gallery, an engraved boulder stands out, displaying geometric signs suggesting a unique representation of a tortoise. Isotopic analysis of calcite crusts on the boulder’s grooves revealed alignment with values found in speleothems from the cave dated to ~37 to 35 ka BP. Additionally, meticulous shape analysis of the grooves’ cross-section and the discernible presence of microlinear scratches on the grooves’ walls confirmed their anthropogenic origin. Examination of stalagmite laminae (36 ka BP) near the engraved boulder revealed a significant presence of wood ash particles within. This finding provides evidence for using fire to illuminate the dark, deep part of the cave during rituals. Acoustic tests conducted in various cave areas indicate that the ritual compound was well suited for communal gatherings, facilitating conversations, speeches, and hearing. Our results underscore the critical role of collective practices centered around a symbolic object in fostering a functional social network within the regional EUP communities.
Origin of fast charging in solid-state batteries revealed by Cryo-transmission X-ray microscopy
Authors: Liu Jiaxuan , Song Yajie , Liu Qingsong , Zhao Wei , An Hanwen , Zhou Zinan , Xu Zihan , Li Menglu , Deng Biao , Wang Jiajun
Published: December 2024

The interface issue poses a limitation on the fast charging of solid-state batteries (SSBs), with the high-impedance non-Faraday electric field serving as a pivotal factor. However, the mechanism of fast-charging capability degradation triggered by the dynamic evolution of non-Faraday electric fields remains unclear due to the lack of particle-scale nondestructive detection techniques. Here, we dissect the generation and elimination processes of non-Faradaic electric field in segments using the developed operando cryogenic transmission X-ray microscopy (Cryo-TXM). This method accurately tracks the ion self-balancing pathways in LiNi
0.8
Co
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Mn
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(NCM811) post-fast-charging, elucidating the high polarization during late charging caused by exacerbated irreversible local electric field. By intermittently applying reverse potential during fast charging to alleviate the exacerbation of non-Faradaic electric field at the cathode interface, we achieved a roughly 400% reversible capacity increase of SSBs at 10 C. This insightful dynamic imaging method effectively captures and resolves the transient, opaque signals within SSBs, significantly enhancing their fast-charging performance.
Global rarity of high-integrity tropical rainforests for threatened and declining terrestrial vertebrates
Authors: Pillay Rajeev , Watson James E.M. , Hansen Andrew J. , Burns Patrick , Virnig Anne Lucy Stilger , Supples Christina , Armenteras Dolors , González-del-Pliego Pamela , Aragon-Osejo Jose , A. Jantz Patrick , Ervin Jamison , Goetz Scott J. , Venter Oscar
Published: December 2024

Structurally intact native forests free from major human pressures are vitally important habitats for the persistence of forest biodiversity. However, the extent of such high-integrity forest habitats remaining for biodiversity is unknown. Here, we quantify the amount of high-integrity tropical rainforests, as a fraction of total forest cover, within the geographic ranges of 16,396 species of terrestrial vertebrates worldwide. We found up to 90% of the humid tropical ranges of forest-dependent vertebrates was encompassed by forest cover. Concerningly, however, merely 25% of these remaining rainforests are of high integrity. Forest-dependent species that are threatened and declining and species with small geographic ranges have disproportionately low proportions of high-integrity forest habitat left. Our work brings much needed attention to the poor quality of much of the forest estate remaining for biodiversity across the humid tropics. The targeted preservation of the world’s remaining high-integrity tropical rainforests that are currently unprotected is a critical conservation priority that may help alleviate the biodiversity crisis in these hyperdiverse and irreplaceable ecosystems. Enhanced efforts worldwide to preserve tropical rainforest integrity are essential to meet the targets of the Convention on Biological Diversity’s 2022 Kunming-Montreal Global Biodiversity Framework which aims to achieve near zero loss of high biodiversity importance areas (including ecosystems of high integrity) by 2030.