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Although spin and charge stripes in high-Tc cuprates have been extensively studied, the exact range of carrier concentration over which they form a static order remains uncertain, complicating efforts to understand their significance. In La2-xSrxCuO4 (LSCO) and in zero external magnetic field, static spin stripes are confined to a doping range well below p*, the pseudogap boundary at zero temperature. However, when high fields suppress the competing effect of superconductivity, spin stripe order is found to extend up to p*. Here, we investigated La1.8-xEu0.2SrxCuO4 (Eu-LSCO) using 139La nuclear magnetic resonance and observe field-dependent spin fluctuations suggesting a similar competition between superconductivity and spin order as in LSCO. Nevertheless, we find that static spin stripes are present practically up to p* irrespective of field strength: the stronger stripe order in Eu-LSCO prevents superconductivity from enforcing a non-magnetic ground state, except very close to p*. Thus, spin-stripe order is consistently bounded by p* in both LSCO and Eu-LSCO, despite their differing balances between stripe order and superconductivity. This indicates that the canonical stripe order, where spins and charges are intertwined in a static pattern, is fundamentally tied to the pseudogap phase. Any stripe order beyond the pseudogap endpoint must then be of a different nature: either spin and charge orders remain intertwined, but both fluctuating, or only spin order fluctuates while charge order remains static. The presence of spin-stripe order up to p*, the pervasive, slow, and field-dependent spin-stripe fluctuations, as well as the electronic inhomogeneity documented in this work, must all be carefully considered in discussions of Fermi surface transformations, quantum criticality, and strange metal behavior.

We present phase-connected timing ephemerides, polarization pulse profiles and Faraday rotation measurements of 12 pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal Radio Astronomy FAST Survey (CRAFTS). The observational data for each pulsar span at least one year. Among them, PSR J1840+2843 shows subpulse drifting, and five pulsars are detected to exhibit pulse nulling phenomena. PSR J0640$-$0139 and PSR J2031$-$1254 are isolated MSPs with stable spin-down rates ($\dot{P}$) of $4.8981(6) \times $10$^{-20}$\,s\,s$^{-1}$ and $6.01(2) \times $10$^{-21}$\,s\,s$^{-1}$, respectively. Additionally, one pulsar (PSR J1602$-$0611) is in a neutron star - white dwarf binary system with 18.23-d orbit and a companion of $\leq$ 0.65M$_{\odot}$. PSR J1602$-$0611 has a spin period, companion mass, and orbital eccentricity that are consistent with the theoretical expectations for MSP - Helium white dwarf (He - WD) systems. Therefore, we believe it might be an MSP-He WD binary system. The locations of PSRs J1751$-$0542 and J1840+2843 on the $P-\dot{P}$ diagram are beyond the traditional death line. This indicates that FAST has discovered some low $\dot{E}$ pulsars, contributing new samples for testing pulsar radiation theories. We estimated the distances of these 12 pulsars based on NE2001 and YMW16 electron density models, and our work enhances the dataset for investigating the electron density model of the Galaxy., Comment: 20 pages, 15 figures, accepted for publication in ApJ

Massive stars end their life as core-collapse supernovae, amongst which some extremes are Type Ic broad-lined supernovae associated with long-duration gamma-ray bursts (LGRBs) having powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. On the other hand, there exists a population of extragalactic fast X-ray transients (EFXTs) with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Known sources that contribute to the observed EFXT population include the softer analogs of LGRBs, shock breakouts of supernovae, or unsuccessful jets. Here, we report the discovery of the bright X-ray transient EP240414a detected by the Einstein Probe (EP), which is associated with the Type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterised by a very soft energy spectrum peaking at < 1.3 keV, which makes it distinct from known LGRBs, X-ray flashes, or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a new population of explosions of Wolf-Rayet stars characterised by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors., Comment: 43 pages, 9 figures, 4 tables, submitted. Comments are welcome

Exchange bias (EB) is a fundamental phenomenon in widespread information technologies. However, a comprehensive understanding of its microscopic origin remains a great challenge. One key issue in the debate is the role of frustration and disorder in the EB mechanism, which motivates the exploration of the EB effect in spin glass (SG) systems. Here,in the SG state of Cr-doped Hund's metal CsFe2As2, we discover a giant EB effect with a maximum bias field of ~ 2 Tesla, which is almost two orders of magnitude larger than that of traditional alloy SGs. Our results indicate that the giant EB effect should originate from the exchange interactions at the natural boundaries between the tunable ferromagnetic-like (FM) regions around Cr dopants and the SG matrix, via which the FM spins are strongly pinned by the frozen spins in the SG matrix. In addition, the temperature-dependent and cooling-field-dependent EB behaviors could be interpreted well by the SG model with frustrated FM/SG boundaries, which provides an intuitive and explicit understanding of the impact of glassy parameters on the EB effect. All these results suggest that the correlated metals are promising directions for exploring the EB effect in the SG state., Comment: 17 pages, 5 figures,Supplementary information available on request

We report the first detection of polarization angle (PA) orthogonal jumps, a phenomenon previously only observed from radio pulsars, from a fast radio burst (FRB) source FRB 20201124A. We find three cases of orthogonal jumps in over two thousand bursts, all resembling those observed in pulsar single pulses. We propose that the jumps are due to the superposition of two orthogonal emission modes that could only be produced in a highly magnetized plasma, and they are caused by the line of sight sweeping across a rotating magnetosphere. The shortest jump timescale is of the order of one-millisecond, which hints that the emission modes come from regions smaller than the light cylinder of most pulsars or magnetars. This discovery provides convincing evidence that FRB emission originates from the complex magnetosphere of a magnetar, suggesting an FRB emission mechanism that is analogous to radio pulsars despite a huge luminosity difference between two types of objects., Comment: 10 pages, 5 figures, accepted by APJL

Long gamma-ray bursts (GRBs) are believed to originate from core collapse of massive stars. High-redshift GRBs can probe the star formation and reionization history of the early universe, but their detection remains rare. Here we report the detection of a GRB triggered in the 0.5--4 keV band by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated as EP240315a, whose bright peak was also detected by the Swift Burst Alert Telescope and Konus-Wind through off-line analyses. At a redshift of $z=4.859$, EP240315a showed a much longer and more complicated light curve in the soft X-ray band than in gamma-rays. Benefiting from a large field-of-view ($\sim$3600 deg$^2$) and a high sensitivity, EP-WXT captured the earlier engine activation and extended late engine activity through a continuous detection. With a peak X-ray flux at the faint end of previously known high-$z$ GRBs, the detection of EP240315a demonstrates the great potential for EP to study the early universe via GRBs., Comment: 41 pages, 8 figures, 7 tables

Epidemic outbreaks can cause critical health concerns and severe global economic crises. For countries or regions with new infectious disease outbreaks, it is essential to generate preventive strategies by learning lessons from others with similar risk profiles. A Strategy Transfer and Decision Support Approach (STDSA) is proposed based on the profile similarity evaluation. There are four steps in this method: (1) The similarity evaluation indicators are determined from three dimensions, i.e., the Basis of National Epidemic Prevention & Control, Social Resilience, and Infection Situation. (2) The data related to the indicators are collected and preprocessed. (3) The first round of screening on the preprocessed dataset is conducted through an improved collaborative filtering algorithm to calculate the preliminary similarity result from the perspective of the infection situation. (4) Finally, the K-Means model is used for the second round of screening to obtain the final similarity values. The approach will be applied to decision-making support in the context of COVID-19. Our results demonstrate that the recommendations generated by the STDSA model are more accurate and aligned better with the actual situation than those produced by pure K-means models. This study will provide new insights into preventing and controlling epidemics in regions that lack experience., Comment: 20 pages, 9 figures

Hund's metal is one kind of correlated metal, in which the electronic correlation is strongly influenced by the Hund's interaction. At high temperatures, while the charge and orbital degrees of freedom are quenched, the spin degrees of freedom can persist in terms of frozen moments. As temperature decreases, a coherent electronic state with characteristic orbital differentiation always emerges at low temperatures through an incoherent-to-coherent crossover, which has been widely observed in iron-based superconductors (e.g., iron selenides and AFe2As2 (A = K, Rb, Cs)). Consequently, the above frozen moments are "screened" by coupling to orbital degrees of freedom, leading to an emergent Fermi-liquid state. In contrast, the coupling among frozen moments should impede the formation of the Fermi-liquid state by competitive magnetic ordering, which is still unexplored in Hund's metal. Here, in the iron-based Hund's metal CsFe2As2, we adopt a chemical substitution at iron sites by Cr/Co atoms to explore the competitive magnetic ordering. By a comprehensive study of resistivity, magnetic susceptibility, specific heat and nuclear magnetic resonance, we demonstrate that the Fermi-liquid state is destroyed in Cr-doped CsFe2As2 by a spinfreezing transition below T_g ~ 22 K. Meanwhile, the evolution of charge degrees of freedom measured by angle-resolved photoemission spectroscopy also supports the competition between the Fermi-liquid state and spin-glass state., Comment: 21 pages, 7 figures

The central engine that powers gamma-ray bursts (GRBs), the most powerful explosions in the universe, is still not identified. Besides hyper-accreting black holes, rapidly spinning and highly magnetized neutron stars, known as millisecond magnetars, have been suggested to power both long and short GRBs. The presence of a magnetar engine following compact star mergers is of particular interest as it would provide essential constraints on the poorly understood equation of state for neutron stars. Indirect indications of a magnetar engine in these merger sources have been observed in the form of plateau features present in the X-ray afterglow light curves of some short GRBs. Additionally, some X-ray transients lacking gamma-ray bursts (GRB-less) have been identified as potential magnetar candidates originating from compact star mergers. Nevertheless, smoking gun evidence is still lacking for a magnetar engine in short GRBs, and the associated theoretical challenges have been addressed. Here we present a comprehensive analysis of the broad-band prompt emission data of a peculiar, very bright GRB 230307A. Despite its apparently long duration, the prompt emission and host galaxy properties point toward a compact star merger origin, being consistent with its association with a kilonova. More intriguingly, an extended X-ray emission component emerges as the $\gamma$-ray emission dies out, signifying the emergence of a magnetar central engine. We also identify an achromatic temporal break in the high-energy band during the prompt emission phase, which was never observed in previous bursts and reveals a narrow jet with half opening angle of approximately $3.4^\circ$., Comment: 44 pages, 10 figures, 5 tables

The Lobster Eye Imager for Astronomy (LEIA), a pathfinder of the Wide-field X-ray Telescope of the Einstein Probe (EP) mission, was successfully launched onboard the SATech-01 satellite of the Chinese Academy of Sciences on 27 July 2022. In this paper, we introduce the design and on-ground test results of the LEIA instrument. Using state-of-the-art Micro-Pore Optics (MPO), a wide field-of-view (FoV) of 346 square degrees (18.6 degrees * 18.6 degrees) of the X-ray imager is realized. An optical assembly composed of 36 MPO chips is used to focus incident X-ray photons, and four large-format complementary metal-oxide semiconductor (CMOS) sensors, each of 6 cm * 6 cm, are used as the focal plane detectors. The instrument has an angular resolution of 4 - 8 arcmin (in FWHM) for the central focal spot of the point spread function, and an effective area of 2 - 3 cm2 at 1 keV in essentially all the directions within the field of view. The detection passband is 0.5 - 4 keV in the soft X-rays and the sensitivity is 2 - 3 * 10-11 erg s-1 cm-2 (about 1 mini-Crab) at 1,000 second observation. The total weight of LEIA is 56 kg and the power is 85 W. The satellite, with a design lifetime of 2 years, operates in a Sun-synchronous orbit of 500 km with an orbital period of 95 minutes. LEIA is paving the way for future missions by verifying in flight the technologies of both novel focusing imaging optics and CMOS sensors for X-ray observation, and by optimizing the working setups of the instrumental parameters. In addition, LEIA is able to carry out scientific observations to find new transients and to monitor known sources in the soft X-ray band, albeit limited useful observing time available., Comment: Accepted by RAA

Angle-resolved photoemission spectroscopy with sub-micrometer spatial resolution ({\mu}-ARPES), has become a powerful tool for studying quantum materials. To achieve sub-micrometer or even nanometer-scale spatial resolution, it is important to focus the incident light beam (usually from the synchrotron radiation) using X-ray optics such as the zone plate or ellipsoidal capillary mirrors. Recently, we developed a laser-based {\mu}-ARPES with spin-resolution (LMS-ARPES). The 177 nm laser beam is achieved by frequency doubling a 355 nm beam using a KBBF crystal and subsequently focused using an optical lens with a focal length of about 16 mm. By characterizing the focused spot size using different methods and performing spatial-scanning photoemission measurement, we confirm the sub-micron spatial resolution of the system. Compared with the {\mu}-ARPES facilities based on synchrotron radiation, our LMS-ARPES system is not only more economical and convenient but also with higher photon flux (> 5E13 photons/s), thus enabling the high-resolution and high-statistics measurements. Moreover, the system is equipped with a two-dimensional spin detector based on exchange scattering at a surface-passivated iron film grown on a W(100) substrate. We investigate the spin structure of the prototype topological insulator Bi2Se3 and reveal a high spin-polarization rate, confirming its spin-momentum locking property. This lab-based LMS-ARPES will be a powerful research tool for studying the local fine electronic structures of different condensed matter systems, including topological quantum materials, mesoscopic materials and structures, and phase-separated materials., Comment: To appear in RSI

As a novel X-ray focusing technology, lobster eye micro-pore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel (1979), the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy ($LEIA$), a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in July 2022, has a mostly un-vignetted field of view of $18.6^\circ \times 18.6^\circ $. Its spatial resolution is in the range of 4$-$7 arcmin in FWHM and the focal spot effective area is 2$-$3 cm$^2$, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1 and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5$-$4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster eye MPO., Comment: 11 pages, 4 figures. Accepted for publication in Astrophysical Journal Letter

Medical data mainly includes various types of biomedical signals and medical images, which can be used by professional doctors to make judgments on patients' health conditions. However, the interpretation of medical data requires a lot of human cost and there may be misjudgments, so many scholars use neural networks and deep learning to classify and study medical data, which can improve the efficiency and accuracy of doctors and detect diseases early for early diagnosis, etc. Therefore, it has a wide range of application prospects. However, traditional neural networks have disadvantages such as high energy consumption and high latency (slow computation speed). This paper presents recent research on signal classification and disease diagnosis based on a third-generation neural network, the spiking neuron network, using medical data including EEG signals, ECG signals, EMG signals and MRI images. The advantages and disadvantages of pulsed neural networks compared with traditional networks are summarized and its development orientation in the future is prospected.

We report the phase-connected timing ephemeris, polarization pulse profiles, Faraday rotation measurements, and Rotating-Vector-Model (RVM) fitting results of twelve millisecond pulsars (MSPs) discovered with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in the Commensal radio Astronomy FAST survey (CRAFTS). The timing campaigns were carried out with FAST and Arecibo over three years. Eleven of the twelve pulsars are in neutron star - white dwarf binary systems, with orbital periods between 2.4 and 100 d. Ten of them have spin periods, companion masses, and orbital eccentricities that are consistent with the theoretical expectations for MSP - Helium white dwarf (He WD) systems. The last binary pulsar (PSR J1912$-$0952) has a significantly smaller spin frequency and a smaller companion mass, the latter could be caused by a low orbital inclination for the system. Its orbital period of 29 days is well within the range of orbital periods where some MSP - He WD systems have shown anomalous eccentricities, however, the eccentricity of PSR J1912$-$0952 is typical of what one finds for the remaining MSP - He WD systems., Comment: 11 pages, 5 figures, MNRAS accepted

Object detection in autonomous driving applications implies that the detection and tracking of semantic objects are commonly native to urban driving environments, as pedestrians and vehicles. One of the major challenges in state-of-the-art deep-learning based object detection are false positives which occur with overconfident scores. This is highly undesirable in autonomous driving and other critical robotic-perception domains because of safety concerns. This paper proposes an approach to alleviate the problem of overconfident predictions by introducing a novel probabilistic layer to deep object detection networks in testing. The suggested approach avoids the traditional Sigmoid or Softmax prediction layer which often produces overconfident predictions. It is demonstrated that the proposed technique reduces overconfidence in the false positives without degrading the performance on the true positives. The approach is validated on the 2D-KITTI objection detection through the YOLOV4 and SECOND (Lidar-based detector). The proposed approach enables interpretable probabilistic predictions without the requirement of re-training the network and therefore is very practical., Comment: This work has been accepted for publication as a REGULAR PAPER in the Transactions on Intelligent Transportation Systems-ITS

Charge exchange between highly charged ions and neutral atoms and molecules has been considered as one of the important mechanisms controlling soft X ray emissions in many astrophysical objects and environments. However, for modeling charge exchange soft X ray emission, the data of n and l resolved state selective capture cross sections are often obtained by empirical and semiclassical theory calculations. With a newly built cold target recoil ion momentum spectroscopy (COLTRIMS) apparatus, we perform a series of measurements of the charge exchange of Ne(8,9)+ ions with He and H2 for collision energy ranging from 1 to 24.75 keV/u. n resolved state selective capture cross-sections are reported. By comparing the measured state selective capture cross sections to those calculated by the multichannel Landau Zener method (MCLZ), it is found that MCLZ calculations are in good agreement with the measurement for the dominant n capture for He target. Furthermore, by using nl resolved cross sections calculated by MCLZ and applying l distributions commonly used in the astrophysical literature to experimentally derived n resolved cross sections, we calculate the soft X ray emissions in the charge exchange between 4 keV/u Ne8+ and He by considering the radiative cascade from the excited Ne7+ ions. Reasonable agreement is found in comparison to the measurement for even and separable models, and MCLZ calculations give results in a better agreement.

The recent discovery of superconductivity in doped infinite-layer nickelates has stimulated intensive interest, especially for similarities and differences compared to that in cuprate superconductors. In contrast to cuprates, although earlier magnetization measurement reveals a Curie-Weiss-like behavior in undoped infinite-layer nickelates, there is no magnetic ordering observed by elastic neutron scattering down to liquid helium temperature. Until now, the nature of the magnetic ground state in undoped infinite-layer nickelates was still elusive. Here, we perform a nuclear magnetic resonance (NMR) experiment through 139La nuclei to study the intrinsic spin susceptibility of infinite-layer LaNiO2. First, the signature for magnetic ordering or freezing is absent in the 139La NMR spectrum down to 0.24 K, which unambiguously confirms a paramagnetic ground state in LaNiO2. Second, a pseudogap-like behavior instead of Curie-Weiss-like behavior is observed in both the temperature-dependent Knight shift and nuclear spin-lattice relaxation rate (1/T1), which is widely observed in both underdoped cuprates and iron-based superconductors. Furthermore, the scaling behavior between the Knight shift and 1/T1T has also been discussed. Finally, the present results imply a considerable exchange interaction in infinite-layer nickelates, which sets a strong constraint for the proposed theoretical models., Comment: 14 pages, 4 figures, accepted by Physical Review Letters

Recently, competing electronic instabilities, including superconductivity and density-wave-like order, have been discovered in vanadium-based kagome metals AV3Sb5 (A = K, Rb, Cs) with a nontrivial band topology. This finding stimulates wide interests to study the interplay of these competing electronic orders and possible exotic excitations in the superconducting state. Here, in order to further clarify the nature of density-wave-like transition in these kagome superconductors, we performed 51V and 133Cs nuclear magnetic resonance (NMR) measurements on the CsV3Sb5 single crystal. A first-order phase transition associated with orbital ordering is revealed by observing a sudden splitting of orbital shift in 51V NMR spectrum at the structural transition temperature Ts ~ 94 K. In contrast, the quadrupole splitting from a charge-density-wave (CDW) order on 51V NMR spectrum only appears gradually below Ts with a typical second-order transition behavior, suggesting that the CDW order is a secondary electronic order. Moreover, combined with 133Cs NMR spectrum, the present result also confirms a three-dimensional structural modulation with a 2ax2ax2c period. Above Ts, the temperature-dependent Knight shift and nuclear spin-lattice relaxation rate (1/T1) further indicate the existence of remarkable magnetic fluctuations from vanadium 3d orbitals, which are suppressed due to orbital ordering below Ts. The present results strongly support that, besides CDW order, the previously claimed density-wave-like transition also involves a dominant orbital order, suggesting a rich orbital physics in these kagome superconductors., Comment: 13 pages, 4 figures, supplementary information available upon request

The non-collinear antiferromagnetic (AFM) structure makes Mn3Sn exhibit exotic properties. At present, it has been found that both the hydrostatic pressure and the strain introduced by interstitial N atoms have a great influence on this magnetic structure. Here, the effect of the residual strain (RS) on it is investigated. AC and DC magnetic measurement results suggest that Mn3Sn without RS has the non-collinear AFM structure only in the temperature range of 285 K to 400 K; while Mn3Sn with RS has a non-coplanar AFM structure in the entire temperature range from 5 K to 400 K. Both anomalous Hall effect and topological Hall effect appears in Mn3Sn with RS, supporting the anticipated non-coplanar AFM structure. Our findings point out a method to realize the chiral non-coplanar AFM structure through the engineering, thereby providing a path for the construction of topological antiferromagnets., Comment: 18 pages, 5 figures

We consider the problem of unsupervised domain adaptation for image classification. To learn target-domain-aware features from the unlabeled data, we create a self-supervised pretext task by augmenting the unlabeled data with a certain type of transformation (specifically, image rotation) and ask the learner to predict the properties of the transformation. However, the obtained feature representation may contain a large amount of irrelevant information with respect to the main task. To provide further guidance, we force the feature representation of the augmented data to be consistent with that of the original data. Intuitively, the consistency introduces additional constraints to representation learning, therefore, the learned representation is more likely to focus on the right information about the main task. Our experimental results validate the proposed method and demonstrate state-of-the-art performance on classical domain adaptation benchmarks. Code is available at https://github.com/Jiaolong/ss-da-consistency., Comment: ICPR 2020

By means of quantum tensor network calculations, we investigate the large Purcell effect experienced by an organic molecule placed in the vicinity of a plasmonic nanostructure. In particular, we consider a donor-{\pi} bridge-acceptor dye at the gap of two Ag nanospheres. Our theoretical approach allows for a realistic description of the continua of both molecular vibrations and optical nanocavity modes. We analyze both the exciton dynamics and the corresponding emission spectrum, showing that these magnitudes are not accurately represented by the simplified models used up to date. By disentangling the molecule coupling to radiative and non-radiative plasmonic modes, we also shed light into the quenching phenomenology taking place in the system.

Here, by conducting a systematic $^{89}$Y NMR study, we explore the nature of the magnetic ground state in a newly discovered iron-based superconductor YFe$_2$Ge$_2$. An incoherent-to-coherent crossover due to the Hund's coupling induced electronic correlation is revealed below the crossover temperature $T^*\sim 75\pm15\,\mathrm{K}$. During the electronic crossover, both the Knight shift ($K$) and the bulk magnetic susceptibility ($\chi$) exhibit a similar nonmonotonic temperature dependence, and a so-called Knight shift anomaly is also revealed by a careful $K$-$\chi$ analysis. Such an electronic crossover has been also observed in heavily hole-doped pnictide superconductors \emph{A}Fe$_2$As$_2$ (\emph{A} = K, Rb, and Cs), which is ascribed to the Hund's coupling induced electronic correlation. Below $T^*$, the spin-lattice relaxation rate divided by temperature $(1/T_1T)$ shows a similar suppression as the Knight shift, suggesting the absence of critical spin fluctuations. This seems to be in conflict with a predicted magnetic quantum critical point (QCP) near this system. However, considering a $\mathbf{q}$-dependent "filter" effect on the transferred hyperfine field, a predominant spin fluctuation with A-type correlation would be perfectly filtered out at $^{89}$Y sites, which is consistent with the recent inelastic neutron scattering results. Therefore, our results confirm that, through a Hund's coupling induced electronic crossover, the magnetic ground state of YFe$_2$Ge$_2$ becomes close to an itinerant magnetic QCP with A-type spin fluctuations. In addition, the possible superconducting pairing due to spin fluctuations is also discussed., Comment: 6 pages, 4 figures, supplementary information available upon request

Superconductivity arises from two distinct quantum phenomena: electron pairing and long-range phase coherence. In conventional superconductors, the two quantum phenomena generally take place simultaneously, while the electron pairing occurs at higher temperature than the long-range phase coherence in the underdoped high-Tc cuprate superconductors. Recently, whether electron pairing is also prior to long-range phase coherence in single-layer FeSe film on SrTiO3 substrate is under debate. Here, by measuring Knight shift and nuclear spin-lattice relaxation rate, we unambiguously reveal a pseudogap behavior below Tp ~ 60 K in two layered FeSe-based superconductors with quasi-two-dimension. In the pseudogap regime, a weak diamagnetic signal and a remarkable Nernst effect are also observed, which indicate that the observed pseudogap behavior is related to superconducting fluctuations. These works confirm that strong phase fluctuation is an important character in the two-dimensional iron-based superconductors as widely observed in high-Tc cuprate superconductors., Comment: 18 pages, 4 figures, supplementary materials available upon request

Scene recognition model based on the DNN and game theory with its applications in human-robot interaction is proposed in this paper. The use of deep learning methods in the field of scene recognition is still in its infancy, but has become an important trend in the future. As the innovative idea of the paper, we propose the following novelties. (1) In this paper, the image registration problem is transformed into a problem of minimum energy in Markov Random Field to finalize the image pre-processing task. Game theory is used to find the optimal. (2) We select neighboring homogeneous sample features and the neighboring heterogeneous sample features for the extracted sample features to build a triple and modify the traditional neural network to propose the novel DNN for scene understanding. (3) The robot control is well combined to guide the robot vision for multiple tasks. The experiment is then conducted to validate the overall performance.

The mechanism of spontaneous exchange bias (SEB) and the dominant factor of its blocking temperature are still unclear in Heusler alloys. Here, the related investigations are performed in Mn2Ni1.5Al0.5 Heusler alloys with SEB. The results of both magnetic measurements and first-principles calculations confirmed that spin frustrated and unfrustrated antiferromagnetic (AFM) states coexist there and they have different magnetic anisotropies, which are essential for SEB. Based on a series of measurement strategies, we demonstrate that the frustrated AFM state undergoes a first-order magnetic transition to the superferromagnet (SFM) state with the help of an external magnetic field, and SFM is retained due to the first-order property of the magnetic transition. SEB originates from the interface coupling of multiple sublattices between the unfrustrated AFM state and SFM state. By analyzing the Arrott plot using the Landau model, we found that the internal field of the system dominates the blocking temperature of SEB, which paves the way for improving the blocking temperature.

The Cold-target recoil-ion momentum spectroscopy (COLTRIMS) has been employed to study the single-electron capture processes in collisions of N3+ ions with He atoms at an impact energy of 30 keV. The relative differential cross sections for the capture to different orbitals of N3+ ions are obtained and are compared with other experiments at low energy. The predictions of the molecular Columbic barrier model have been made. From the longitudinal momentum spectrum of recoil ions, the different electronic configuration was identified and the metastable projectile ions were distinguished. The single electron capture into the N2+ (1s22s22p 2P) state from the ground state N3+ (1s22s2 1S) projectile is the dominant reaction channel. The fraction of the metastable state N3+(2s2p 3P) of the incident projectile beam is about 46%.

The importance of the spin-orbit coupling (SOC) effect in Fe-based superconductors (FeSCs) has recently been under hot debate. Considering the Hund's coupling-induced electronic correlation, the understanding of the role of SOC in FeSCs is not trivial and is still elusive. Here, through a comprehensive study of 77Se and 57Fe nuclear magnetic resonance, a nontrivial SOC effect is revealed in the nematic state of FeSe. First, the orbital-dependent spin susceptibility, determined by the anisotropy of the 57Fe Knight shift, indicates a predominant role from the 3dxy orbital, which suggests the coexistence of local and itinerant spin degrees of freedom (d.o.f.) in the FeSe. Then, we reconfirm that the orbital reconstruction below the nematic transition temperature (Tnem ~ 90 K) happens not only on the 3dxz and 3dyz orbitals but also on the 3dxy orbital, which is beyond a trivial ferro-orbital order picture. Moreover, our results also indicate the development of a coherent coupling between the local and itinerant spin d.o.f. below Tnem, which is ascribed to a Hund's coupling-induced electronic crossover on the 3dxy orbital. Finally, due to a nontrivial SOC effect, sizable in-plane anisotropy of the spin susceptibility emerges in the nematic state, suggesting a spin-orbital-intertwined nematicity rather than simply spin- or orbital-driven nematicity}. The present work not only reveals a nontrivial SOC effect in the nematic state but also sheds light on the mechanism of nematic transition in FeSe., Comment: 11 pages, 5 figures, supplementary information available upon request

In low-dimensional metallic systems, lattice distortion is usually coupled to a density-wave-like electronic instability due to Fermi surface nesting (FSN) and strong electron-phonon coupling. However, the ordering of other electronic degrees of freedom can also occur simultaneously with the lattice distortion thus challenges the aforementioned prevailing scenario. Recently, a hidden electronic reconstruction beyond FSN was revealed in a layered metallic compound BaTi2As2O below the structural transition temperature Ts ~ 200 K. The nature of this hidden electronic instability is under strong debate. Here, by measuring the local orbital polarization through 75As nuclear magnetic resonance experiment, we observe a p-d bond order between Ti and As atoms in BaTi2As2O single crystal. Below Ts, the bond order breaks both rotational and translational symmetry of the lattice. Meanwhile, the spin-lattice relaxation measurement indicates a substantial loss of density of states and an enhanced spin fluctuation in the bond-order state. Further first-principles calculations suggest that the mechanism of the bond order is due to the coupling of lattice and nematic instabilities. Our results strongly support a bond-order driven electronic reconstruction in BaTi2As2O and shed light on the mechanism of superconductivity in this family., Comment: 7 pages, 4 figures, supplemental material available upon request

Although Fe-based superconductors are multiorbital correlated electronic systems, previous nuclei magnetic resonance (NMR) measurement suggests that a single spin-fluid model is sufficient to describe its spin behavior. Here, we firstly observed the breakdown of single spin-fluid model in a heavily hole-doped Fe-based superconductor CsFe2As2 by site-selective NMR measurement. At high temperature regime, both of Knight shift and nuclei spin-lattice relaxation at 133Cs and 75As nuclei exhibit distinct temperature-dependent behavior, suggesting the breakdown of single spin-fluid model in CsFe2As2. This is ascribed to the coexistence of both localized and itinerant spin degree of freedom at 3d orbits, which is consistent with orbital-selective Mott phase. However, single spin-fluid behavior is gradually recovered by developing a coherent state among 3d orbits with decreasing temperature. A Kondo liquid scenario is proposed for the low-temperature coherent state. The present work sets strong constraint on the theoretical model for Fe-based superconductors., Comment: 5 pages, 3 figures, all comments are welcome

In correlated electrons system, quantum melting of electronic crystalline phase often gives rise to many novel electronic phases. In cuprates superconductors, melting the Mott insulating phase with carrier doping leads to a quantum version of liquid crystal phase, the electronic nematicity, which breaks the rotational symmetry and exhibits a tight twist with high-temperature superconductivity. Recently, the electronic nematicity has also been observed in Fe-based superconductors. However, whether it shares a similar scenario with its cuprates counterpart is still elusive. Here, by measuring nuclear magnetic resonance in CsFe2As2, a prototypical Fe-based superconductor perceived to have evolved from a Mott insulating phase at 3d5 configuration, we report anisotropic quadruple broadening effect as a direct result of local rotational symmetry breaking. For the first time, clear connection between the Mott insulating phase and the electronic nematicity can be established and generalized to the Fe-based superconductors. This finding would promote a universal understanding on electronic nematicity and its relation with high-temperature superconductivity., Comment: 14 pages, 4 figures

China Spallation Neutron Source (CSNS) is the first high-performance pulsed neutron source in China, which will meet the increasing fundamental research and technique applications demands domestically and overseas. A new distributed data processing and analysis environment has been developed, which has generic functionalities for neutron scattering experiments. The environment consists of three parts, an object-oriented data processing framework adopting a data centered architecture, a communication and data caching system based on the C/S paradigm, and data analysis and visualization software providing the 2D/3D experimental data display. This environment will be widely applied in CSNS for live data processing., Comment: 13 pages, 8 figures

Recently there have been increasingly hot debates on whether a bulk Fermi surface of charge-neutral excitations exists in the topological Kondo insulator SmB6. To unambiguously resolve this issue, we performed the low-temperature thermal conductivity measurements of a high-quality SmB6 single crystal down to 0.1 K and up to 14.5 T. Our experiments show that the residual linear term of thermal conductivity at zero field is zero, within the experimental accuracy. Furthermore, the thermal conductivity is insensitive to magnetic field up to 14.5 T. These results exclude the existence of fermionic charge-neutral excitations in bulk SmB6, such as scalar Majorana fermions or spinons, thus put a strong constraint on the explanation of the quantum oscillations observed in SmB6., Comment: 5 pages, 3 figures

Unconventional superconductivity from heavy fermion (HF) is always observed in f-electron systems, in which Kondo physics between localized f-electrons and itinerant electrons plays an essential role. Whether HF superconductivity could be achieved in other systems without f electrons, especially for d-electron systems, is still elusive. Here, we experimentally study the origin of d-electron HF behavior in iron-based superconductors (FeSCs) AFe2As2 (A = K, Rb, Cs). Nuclear magnetic resonance on 75As reveals a universal coherent-incoherent crossover with a characteristic temperature T*. Below T*, a so-called 'Knight shift anomaly' is first observed in FeSCs, which exhibits a scaling behavior similar to f-electron HF materials. Furthermore, the scaling rule also regulates the manifestation of magnetic fluctuation. These results undoubtedly support an emergent Kondo scenario for the d-electron HF behavior, which suggests the AFe2As2 (A = K, Rb, Cs) as the first material realization of d-electron HF superconductors., Comment: 15 pages, 4 figures, including supplementary information with 9 figures

Einstein Probe is a small mission dedicated to time-domain high-energy astrophysics. Its primary goals are to discover high-energy transients and to monitor variable objects in the $0.5-4~$keV X-rays, at higher sensitivity by one order of magnitude than those of the ones currently in orbit. Its wide-field imaging capability, featuring a large instantaneous field-of-view ($60^\circ \times60^\circ$, $\sim1.1$sr), is achieved by using established technology of micro-pore (MPO) lobster-eye optics, thereby offering unprecedentedly high sensitivity and large Grasp. To complement this powerful monitoring ability, it also carries a narrow-field, sensitive follow-up X-ray telescope based on the same MPO technology to perform follow-up observations of newly-discovered transients. Public transient alerts will be downlinked rapidly, so as to trigger multi-wavelength follow-up observations from the world-wide community. Over three of its 97-minute orbits almost the entire night sky will be sampled, with cadences ranging from 5 to 25 times per day. The scientific objectives of the mission are: to discover otherwise quiescent black holes over all astrophysical mass scales by detecting their rare X-ray transient flares, particularly tidal disruption of stars by massive black holes at galactic centers; to detect and precisely locate the electromagnetic sources of gravitational-wave transients; to carry out systematic surveys of X-ray transients and characterize the variability of X-ray sources. Einstein Probe has been selected as a candidate mission of priority (no further selection needed) in the Space Science Programme of the Chinese Academy of Sciences, aiming for launch around 2020., Comment: accepted to publish in PoS, Proceedings of "Swift: 10 Years of Discovery" (Proceedings of Science; ed. by P. Caraveo, P. D'Avanzo, N. Gehrels and G. Tagliaferri). Minor changes in text, references updated

FeSe-derived superconductors show some unique behaviors relative to iron-pnictide superconductors, which are very helpful to understand the mechanism of superconductivity in high-Tc iron-based superconductors. The low-energy electronic structure of the heavily electron-doped AxFe2Se2 (A=K, Rb, Cs) demonstrates that interband scattering or Fermi surface nesting is not a necessary ingredient for the unconventional superconductivity in iron-based superconductors. The superconducting transition temperature (Tc) in the one-unit-cell FeSe on SrTiO3 substrate can reach as high as ~65 K, largely transcending the bulk Tc of all known iron-based superconductors. However, in the case of AxFe2Se2, the inter-grown antiferromagnetic insulating phase makes it difficult to study the underlying physics. Superconductors of alkali metal ions and NH3 molecules or organic-molecules intercalated FeSe and single layer or thin film FeSe on SrTiO3 substrate are extremely air-sensitive, which prevents the further investigation of their physical properties. Therefore, it is urgent to find a stable and accessible FeSe-derived superconductor for physical property measurements so as to study the underlying mechanism of superconductivity. Here, we report the air-stable superconductor (Li0.8Fe0.2)OHFeSe with high temperature superconductivity at ~40 K synthesized by a novel hydrothermal method. The crystal structure is unambiguously determined by the combination of X-ray and neutron powder diffraction and nuclear magnetic resonance. It is also found that an antiferromagnetic order coexists with superconductivity in such new FeSe-derived superconductor. This novel synthetic route opens a new avenue for exploring other superconductors in the related systems. The combination of different structure characterization techniques helps to complementarily determine and understand the details of the complicated structures.

We report the detection of eight vibronic bands of C$_3$, seven of which have been hitherto unobserved in astrophysical objects, in the translucent cloud towards HD~169454. Four of these bands are also found towards two additional objects: HD~73882 and HD~154368. Very high signal-to-noise ratio ($\sim$1000 and higher) and high resolving power ($R=80,000$) UVES-VLT spectra (Paranal, Chile) allow for detecting novel spectral features of C$_3$, even revealing weak perturbed features in the strongest bands. The work presented here provides the most complete spectroscopic survey of the so far largest carbon chain detected in translucent interstellar clouds. High-quality laboratory spectra of C$_3$ are measured using cavity ring-down absorption spectroscopy in a supersonically expanding hydrocarbon plasma, to support the analysis of the identified bands towards HD~169454. A column density of N(C$_3$) = $(6.6 \pm 0.2) \times 10^{12}$ cm$^{-2}$ is inferred and the excitation of the molecule exhibits two temperature components; $T_{exc}= 22 \pm 1$ K for the low-$J$ states and $T_{exc}= 187 \pm 25$ K for the high-$J$ tail. The rotational excitation of C$_3$ is reasonably well explained by models involving a mechanism including inelastic collisions, formation and destruction of the molecule, and radiative pumping in the far-infrared. These models yield gas kinetic temperatures comparable to those found for $T_{exc}$. The assignment of spectral features in the UV-blue range 3793-4054 \AA\ may be of relevance for future studies aiming at unravelling spectra to identify interstellar molecules associated with the diffuse interstellar bands (DIBs)., Comment: 15 pages, 13 figures, submitted to MNRAS

Recently, the resistance saturation at low temperature in Kondo insulator SmB6, a long-standing puzzle in condensed matter physics, was proposed to originate from topological surface state. Here,we systematically studied the magnetoresistance of SmB6 at low temperature up to 55 Tesla. Both temperature- and angular-dependent magnetoresistances show a similar crossover behavior below 5 K. Furthermore, the angular-dependent magnetoresistance on different crystal face confirms a two-dimensional surface state as the origin of magnetoresistances crossover below 5K. Based on two-channels model consisting of both surface and bulk states, the field-dependence of bulk gap with critical magnetic field (Hc) of 196 T is extracted from our temperature-dependent resistance under different magnetic fields. Our results give a consistent picture to understand the low-temperature transport behavior in SmB6, consistent with topological Kondo insulator scenario., Comment: 5 pages, 5 figures

The longitudinal Schottky spectra of a radio-frequency (RF) bunched and electron cooled 22Ne10+ ion beam at 70 MeV/u have been studied by a newly installed resonant Schottky pick-up at the experimental cooler storage ring (CSRe), at IMP. For an RF-bunched ion beam, a longitudinal momentum spread of has been reached with less than 107 stored ions. The reduction of momentum spread compared with coasting ion beam was observed from Schottky noise signal of the bunched ion beam. In order to prepare the future laser cooling experiment at the CSRe, the RF-bunching power was modulated at 25th, 50th and 75th harmonic of the revolution frequency, effective bunching amplitudes were extracted from the Schottky spectrum analysis. Applications of Schottky noise for measuring beam lifetime with ultra-low intensity of ion beams are presented, and it is relevant to upcoming experiments on laser cooling of relativistic heavy ion beams and nuclear physics at the CSRe., Comment: to be published in Chinese Physics C

A large amount of observations have constrained cosmological parameters and the initial density fluctuation spectrum to a very high accuracy. However, cosmological parameters change with time and the power index of the power spectrum varies with mass scale dramatically in the so-called concordance Lambda CDM cosmology. Thus, any successful model for its structural evolution should work well simultaneously for various cosmological models and different power spectra. We use a large set of high-resolution N-body simulations of a variety of structure formation models (scale-free, standard CDM, open CDM, and Lambda CDM) to study the mass accretion histories (MAHs), the mass and redshift dependence of concentrations and the concentration evolution histories of dark matter halos. We find that there is significant disagreement between the much-used empirical models in the literature and our simulations. According to two simple but tight correlations we find from the simulation results, we develop new empirical models for both the MAHs and the concentration evolution histories of dark matter halos, and the latter can also be used to predict the mass and redshift dependence of halo concentrations. These models are accurate and universal: the same set of model parameters works well for different cosmological models and for halos of different masses at different redshifts and the model predictions are highly accurate even when the histories are traced to very high redshift. These models are also simple and easy to implement. A web calculator and a user-friendly code to make the relevant calculations are available from http://www.shao.ac.cn/dhzhao/mandc.html . We explain why Lambda CDM halos on nearly all mass scales show two distinct phases in their evolution histories., Comment: 17 pages, including 22 figures, publicated in ApJ; V2: some new figures added; V3: some typo fixed

We have accurately measured the bispectrum for four scale-free models of structure formation with the spectral index $n=1$, 0, -1, and -2. The measurement is based on a new method that can effectively eliminate the alias and numerical artifacts, and reliably extend the analysis into the strongly non-linear regime. The work makes use of a set of state-of-the art N-body simulations that have significantly increased the resolution range compared with the previous studies on the subject. With these measured results, we demonstrated that the measured bispectrum depends on the shape and size of $k$-triangle even in the strongly nonlinear regime. It increases with wavenumber and decreases with the spectral index. These results are in contrast with the hypothesis that the reduced bispectrum is a constant in the strongly non-linear regime. We also show that the fitting formula of Scoccimarro & Frieman (1999) does not describe our simulation results well (with a typical error about 40 percent). In the end, we present a new fitting formula for the reduced bispectrum that is valid for $-2 \leq n \leq 0$ with a typical error of 10 percent only., Comment: 33 pages, including 1 table, 14 figures, accepted by ApJ

Using a combination of N-body simulations with different resolutions, we study in detail how the concentrations of cold dark matter (CDM) halos depend on halo mass at different redshifts. We confirm that halo concentrations at the present time depend strongly on halo mass, but our results also show marked differences from the predictions of some early empirical models. Our main result is that the mass dependence of the concentrations becomes weaker at higher redshifts, and at z >~ 3 halos of mass greater than 10^{11} Msun/h all have a similar median concentration, c ~ 3.5. While the median concentrations of low-mass halos grow significantly with time, those of massive halos change only little with redshifts. These results are quantitatively in good agreement with the empirical model proposed by Zhao et al. which shows that halos in the early fast accretion phase all have similar concentrations., Comment: 11 pages, including 2 figures and 1 table, publicated in ApJL, the first paper stating the zero mass-dependence of concentrations for massive and/or high redshift dark matter halos, which are still in the fast growth phase, quoted by the second version of ; v2: references corrected to be the same as the published version

We investigate the feasibility of determining the pairwise velocity dispersion (PVD) for Lyman Break Galaxies (LBGs), and of using this quantity as a discriminator among theoretical models. We find that when the Two Point Correlation Function over the range of observable separations is fixed, different schemes of galaxy formation will lead to significant changes in PVD, while influence of different cosmogonies is invisible. Our test with mock samples shows furthermore that one can discriminate among such models already with currently available observational samples (if the measurement error of the redshift is negligible) which have a typical error of $80\kms$. The error will be reduced by a factor of 2 if the samples are increased four times. We also show that an erroneous assumption about the geometry of the universe and different infall models only slightly change the results. Therefore the PVD will become another promising statistic to test galaxy formation models with redshift samples of LBGs., Comment: 29 pages, 12 figures, 1 tables. Accepted for publication in ApJ

The recent search for non $q \bar{q}$ mesons in $\pi^{-}p$ interactions at Brookhaven National Laboratory is summarized. Many final states such as $\eta \pi$, $\eta' \pi^{-}$, $a_{0} \pi$, $f_{1} \pi$, $a_{2} \pi$, $b_{1} \pi$, which are favored decay modes of exotics, are under investigation., Comment: 9 pages, PostScript, Presented at the International School of Nuclear Physics, Erice, Sicily, Italy, September 1995

Continuous fiber composites have shown tremendous promise in industrial applications. Their microstructures, however, are very complex and in many instances difficult to characterize. In this project, the fracture characteristics of a specially made fiber reinforced composite with different fiber spacing are investigated. The experimental results so far have shown that after an initial transient phase the crack speed reaches a steady phase, i.e., independent of the crack length. Within the steady crack growth phase debonding along the fibers in the bridging zone grows in a self-similar manner. During the steady phase the energy dissipation per cycle is constant. Afterwards, an increase of the energy dissipation is observed that is accompanied by a decrease in crack speed. This latter trend is presumed to be the result of relatively large amounts of energy dissipated in the bulk of the specimen. Using appropriate Green's function and computer simulations, the stress intensity factor at the crack tip is evaluated for various cases of bridging stresses. In this way the effects of specimen size and fiber spacing on the overall fracture behavior of the composite system are analyzed. The steady crack speed and the steady rate of debonding have a similar power dependence on stress level. Dimensional analysis demonstrates that the particular fracture process is not governed by dimensional invariance but on the detailed micromechanisms in the bridging zone.