High-resolution time-and angle-resolved photoemission measurements were conducted on the topological insulator ZrTe_(5).With strong femtosecond photoexcitation,a possible ultrafast phase transition from a weak to a st...High-resolution time-and angle-resolved photoemission measurements were conducted on the topological insulator ZrTe_(5).With strong femtosecond photoexcitation,a possible ultrafast phase transition from a weak to a strong topological insulating phase was experimentally realized by recovering the energy gap inversion in a time scale that was shorter than 0.15 ps.This photoinduced transient strong topological phase can last longer than 2 ps at the highest excitation fluence studied,and it cannot be attributed to the photoinduced heating of electrons or modification of the conduction band filling.Additionally,the measured unoccupied electronic states are consistent with the first-principles calculation based on experimental crystal lattice constants,which favor a strong topological insulating phase.These findings provide new insights into the longstanding controversy about the strong and weak topological properties in ZrTe_(5),and they suggest that many-body effects including electron–electron interactions must be taken into account to understand the equilibrium weak topological insulating phase in ZrTe_(5).展开更多
We report a study of the electronic structure of BaFe_(2)As_(2) under uniaxial strains using angle-resolved photoemission spectroscopy and transport measurements. Two electron bands at the MY point, with an energy spl...We report a study of the electronic structure of BaFe_(2)As_(2) under uniaxial strains using angle-resolved photoemission spectroscopy and transport measurements. Two electron bands at the MY point, with an energy splitting of 50 meV in the strain-free sample, shift downward and merge into each other under a large uniaxial strain, while three hole bands at theГ point shift downward together. However, we also observed an enhancement of the resistance anisotropy under uniaxial strains by electrical transport measurements, implying that the applied strains strengthen the electronic nematic order in BaFe_(2)As_(2). These observations suggest that the splitting of these two electron bands at the MY point is not caused by the nematic order in BaFe_(2)As_(2).展开更多
The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states...The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states host great potential for future applications in high-speed and low-consumption electronic devices.Despite being extensively investigated,practical platforms are still scarce.In this work,with molecular beam epitaxy(MBE),we provide the first experimental report on high-quality Bi(110)/CrTe_(2) magnetic heterostructure.By employing in-situ high-resolution scanning tunneling microscopy,we are able to examine the interaction between magnetism and topology.There is a potential edge state at an energy level above the Fermi level,but no edge states observed near the Fermi level The absence of high-order topological corner states near EF highlights the importance of lattice matching and interface engineering in designing high-order topological states.Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.展开更多
The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a di...The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.展开更多
High-power intense optical sources in the mid-to-long wavelength infrared region are very attractive for a wide range of fields from fundamental research to materials science and biology applications.However,there are...High-power intense optical sources in the mid-to-long wavelength infrared region are very attractive for a wide range of fields from fundamental research to materials science and biology applications.However,there are still significant challenges in extending long-wavelength infrared pulses into the relativistic regime using conventional optical techniques.Here,based upon a new type of plasma-based optical method,we present an efficient scheme capable of combining several high-power long-wavelength infrared laser pulses into one single,more intense pulse,thus bringing the intensity of the output pulse to the relativistic regime.Such intense infrared pulses will open up new possibilities for strong-field physics and ultrafast applications.Furthermore,this is beneficial to understand the underlying physics and nonlinear processes of modulation,propagation and energy transfer of high-power intense laser pulses in plasmas.展开更多
Motivated by the mathematical beauty and the recent experimental realizations of fractal systems,we study the spin-1/2 antiferromagnetic Heisenberg model on a Sierpiński gasket.The fractal porous feature generates ne...Motivated by the mathematical beauty and the recent experimental realizations of fractal systems,we study the spin-1/2 antiferromagnetic Heisenberg model on a Sierpiński gasket.The fractal porous feature generates new kinds of frustration to exhibit exotic quantum states.Using advanced tensor network techniques,we identify a quantum gapless-spin-liquid ground state in fractional spatial dimension.This fractal spin system also demonstrates nontrivial nonlocal properties.While the extremely short-range correlation causes a highly degenerate spin form factor,the entanglement in this fractal system suggests a long-range scaling behavior.We also study the dynamic structure factor and clearly identify the gapless excitation with a stable corner excitation emerged from the ground-state entanglement.Our results unambiguously point out multiple essential properties of this fractal spin system,and open a new route to explore spin liquid and frustrated magnetism.展开更多
Very high energy(VHE)photons may have a higher survival rate than that expected in standard-model physics,as suggested by the recently reported gamma ray burst GRB221009A.While a photon-axion like particle(ALP)oscilla...Very high energy(VHE)photons may have a higher survival rate than that expected in standard-model physics,as suggested by the recently reported gamma ray burst GRB221009A.While a photon-axion like particle(ALP)oscillation can boost the survival rate of the VHE photons,current works have not been based on concrete particle models,leaving the identity of the corresponding ALP unclear.Here,we show that the required ALP scenario is consistent with the electroweak axion with an anomaly free Z_(10)Froggatt–Nielsen symmetry.展开更多
Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model f...Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model for the radio eclipse by calculating the geometry of the bow shock between the winds of the pulsar and companion,where the shock shapes the eclipsing medium but had not been described in detail in previous works.The model is further used to explain the variations of the flux density and dispersion measure of three BW pulsars(i.e.,PSR B1957+20,J2055+3829,and J2051-0827)detected by the Five-hundred-meter Aperture Spherical radio Telescope.Consequently,we constrained the parameters of the three BW systems such as the inclination angles and true anomalies of the observer as well as the mass-loss rates and wind velocity of the companion stars.With the help of these constraints,it is expected that magnetic fields of companion stars and even masses of pulsars could further be determined as some extra observation can be achieved in the future.展开更多
We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inver...We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inversion in Fe1+yTexSe1-x,which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-xwith excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.展开更多
Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms invo...Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.展开更多
We report the laser-chirp controlled terahertz(THz) wave generation from two-color-laser-induced air plasma.Our experimental results reveal that the THz wave is affected by both the laser energy and chirp,leading to r...We report the laser-chirp controlled terahertz(THz) wave generation from two-color-laser-induced air plasma.Our experimental results reveal that the THz wave is affected by both the laser energy and chirp,leading to radiation minima that can be quantitatively reconstructed using the linear-dipole-array model.The phase difference between the two colors,determined by the chirp and intensity of the laser,can account for the radiation minima.Furthermore,we observe an asynchronous variation in the generated THz spectrum,which suggests a THz frequency-dependent phase matching between the laser pulse and THz wave.These results highlight the importance of laser chirp during the THz wave generation and demonstrate the possibility of modulating the THz yields and spectrum through chirping the incident laser pulse.This work can provide valuable insights into the mechanism of plasma-based THz wave generation and offer a unique means to control THz emissions.展开更多
YbMnBi2 is a recently discovered time-reversal-symmetry breaking type-Ⅱ Weyl semimetal.However, as a representation of the new category of topological matters, the scanning tunneling microcopy(STM) results on such im...YbMnBi2 is a recently discovered time-reversal-symmetry breaking type-Ⅱ Weyl semimetal.However, as a representation of the new category of topological matters, the scanning tunneling microcopy(STM) results on such important material are still absent.Here, we report the STM investigations on the morphology of vacuum cleaved single crystalline YbMnBi2 samples.A hill and valley type of topography is observed on the YbMnBi2 surface, which is consistent with the non-layer nature of its crystal structure.Analysis of STM images yields the information of the index of the vicinal surface.Our results here lay a playground of future atomic scale research on YbMnBi2.展开更多
Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal spec...Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal speckles,the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles.The wave coupling can be further weakened by the random polarization of such beams.Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of∼1%as compared with a monochromatic laser beam.Consequently,the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers.Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.展开更多
In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–...In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.展开更多
Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic proper...Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic properties of galaxies, such as concentration, morphology, specific star formation rate(sSFR),and bulge fraction, and on the large-scale environments in the context of central/satellite decomposition,halo environment, the cosmic web: cluster, filament, sheet and void, as well as galaxy number density. We find that there is a strong dependence of the luminosity-or mass-size relation on the galaxy concentration, morphology, s SFR and bulge fraction. Compared with late-type(spiral) galaxies, there is a clear trend of smaller sizes and steeper slope for early-type(elliptical) galaxies. Similarly, galaxies with a high bulge fraction have smaller sizes and steeper slopes than those with a low bulge fraction. Fitting formulae of the average luminosity-and mass-size relations are provided for galaxies with these different intrinsic properties. Examining galaxies in terms of their large scale environments, we find that the masssize relation has some weak dependence on the halo mass and central/satellite segregation for galaxies within mass range 9.0 ≤ log M*≤ 10.5, where satellites or galaxies in more massive halos have slightly smaller sizes than their counterparts, while the cosmic web and local number density dependence of the mass-size relation is almost negligible.展开更多
We focus on a series of f(R) gravity theories in Palatini formalism to investigate the probabilities of producing late-time acceleration for the flat Friedmann-Robertson-Walker(FRW) universe.We apply a statefinder dia...We focus on a series of f(R) gravity theories in Palatini formalism to investigate the probabilities of producing late-time acceleration for the flat Friedmann-Robertson-Walker(FRW) universe.We apply a statefinder diagnostic to these cosmological models for chosen series of parameters to see if they can be distinguished from one another. The diagnostic involves the statefinder pair{r,s},where r is derived from the scale factor a and its higher derivatives with respect to the cosmic time t,and s is expressed by r and the deceleration parameter q. In conclusion,we find that although two types of f(R) theories:(i) f(R) = R + αR^m-βR^(-n) and(ii) f(R) = R + α lnR-β can lead to late-time acceleration,their evolutionary trajectories in the r-s and r-q planes reveal different evolutionary properties,which certainly justify the merits of the statefinder diagnostic. Additionally,we utilize the observational Hubble parameter data(OHD) to constrain these models of f(R) gravity. As a result,except for m = n = 1/2 in case(i),α = 0 in case(i) and case(ii) allow the ΛCDM model to exist in the 1σ confidence region. After applying the statefinder diagnostic to the best-fit models,we find that all the best-fit models are capable of going through the deceleration/acceleration transition stage with a late-time acceleration epoch,and all these models turn to the de Sitter point({r,s}={1,0}) in the future. Also,the evolutionary differences between these models are distinct,especially in the r-s plane,which makes the statefinder diagnostic more reliable in discriminating cosmological models.展开更多
Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure ga...Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure galaxy clustering.In this paper,by virtue of the mock galaxy catalogs,we investigate the effect of two redshift assignment methods on the measurement of galaxy two-point correlation functions(hereafter 2 PCFs),the Vmax method and the"shuffled"method.We have found that the shuffled method significantly underestimates both of the projected 2 PCFs and the two-dimensional 2 PCFs in redshift space,while the Vmax method does not show any notable bias on the 2 PCFs for volume-limited samples.For fluxlimited samples,the bias produced by the Vmax method is less than half of the shuffled method on large scales.Therefore,we strongly recommend the Vmax method to assign redshifts to random samples in the future galaxy clustering analysis.展开更多
To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The r...To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The radioactivity of the proposed hydrophone is strictly controlled by selecting pure raw materials, especially active piezoelectric ceramics. The electroacoustic performance of the hydrophone is improved by making structural optimization. High sensitivity and aimed directivity are achieved using 33-mode piezoelectric ceramic rings arranged in series and improvement in the radiating head of the Tonpilz hydrophone, respectively. All electroacoustic performances are studied through finite element analyses.The simulations indicate that the electroacoustic performances of the hydrophones in linear alkylbenzene-based liquid scintillator can be approximately predicted according to the results in water because their differences caused by two types of acoustic media, water and liquid scintillator, are known. The tests show that the hydrophone prototype can achieve a maximum sensitivity of-209.3dB and a beamwidth of 132.2° at a frequency of 143 kHz.In addition, eight hydrophones only contributed to a background radioactivity level of 26 ± 4 mHz in the neutrino analysis.展开更多
Using high-resolution angle-resolved and time-resolved photoemission spectroscopy,we have studied the low-energy band structures in occupied and unoccupied states of three ternary compounds GeBi_(2)Te_(4),SnBi_(2)Te_(...Using high-resolution angle-resolved and time-resolved photoemission spectroscopy,we have studied the low-energy band structures in occupied and unoccupied states of three ternary compounds GeBi_(2)Te_(4),SnBi_(2)Te_(4) and Sn_(0.571)Bi_(2.286)Se_(4) near the Fermi level.In previously confirmed topological insulator GeBi_(2)Te_(4) compounds,we confirmed the existence of the Dirac surface state and found that the bulk energy gap is much larger than that in the first-principles calculations.In SnBi_(2)Te_(4) compounds,the Dirac surface state was observed,consistent with the first-principles calculations,indicating that it is a topological insulator.The experimental detected bulk gap is a little bit larger than that in calculations.In Sn_(0.571)Bi_(2.286)Se_(4) compounds,our measurements suggest that this nonstoichiometric compound is a topological insulator although the stoichiometric SnBi_(2)Se_(4) compound was proposed to be topological trivial.展开更多
The star formation rate function(SFRF) and specific star formation rate function(s SFRF) from observations are impacted by the Eddington bias, due to uncertainties in the estimated star formation rate(SFR). We develop...The star formation rate function(SFRF) and specific star formation rate function(s SFRF) from observations are impacted by the Eddington bias, due to uncertainties in the estimated star formation rate(SFR). We develop a novel method to correct the Eddington bias and obtain the intrinsic SFRF and sSFRF from the Sloan Digital Sky Survey(SDSS) Data Release 7. The intrinsic SFRF is in good agreement with measurements from previous data in the literature that relied on UV SFRs but its high star-forming end is slightly lower than the corresponding IR and radio tracers. We demonstrate that the intrinsic sSFRF from SDSS has a bimodal form with one peak found at sSFR ~10-9.7 yr^-1 representing the star-forming objects while the other peak is found at sSFR ~10-12 yr^-1 representing the quenched population. Furthermore, we compare our observations with the predictions from the Illustris TNG and Illustris simulations and affirm that the "TNG" model performs much better than its predecessor. However,we show that the simulated SFRF and CSFRD of TNG simulations are highly dependent on resolution,reflecting the limitations of the model and today’s state-of-the-art simulations. We demonstrate that the bimodal, two peaked s SFRF implied by the SDSS observations does not appear in TNG regardless of the adopted box-size or resolution. This tension reflects the need for inclusion of an additional efficient quenching mechanism in the TNG model.展开更多
基金support from the National Key R&D Program of China(Grant Nos.2021YFA1400202 and 2021YFA1401800)the National Natural Science Foundation of China(Grant Nos.12141404 and 11974243)+3 种基金the Natural Science Foundation of Shanghai(Grant Nos.22ZR1479700 and 23XD1422200)support from the China Postdoctoral Science Foundation(Grant No.2022M722108)support from the National Key R&D Program of China(Grant Nos.2022YFA1402400 and 2021YFA1400100)the National Natural Science Foundation of China(Grant No.12074248)。
文摘High-resolution time-and angle-resolved photoemission measurements were conducted on the topological insulator ZrTe_(5).With strong femtosecond photoexcitation,a possible ultrafast phase transition from a weak to a strong topological insulating phase was experimentally realized by recovering the energy gap inversion in a time scale that was shorter than 0.15 ps.This photoinduced transient strong topological phase can last longer than 2 ps at the highest excitation fluence studied,and it cannot be attributed to the photoinduced heating of electrons or modification of the conduction band filling.Additionally,the measured unoccupied electronic states are consistent with the first-principles calculation based on experimental crystal lattice constants,which favor a strong topological insulating phase.These findings provide new insights into the longstanding controversy about the strong and weak topological properties in ZrTe_(5),and they suggest that many-body effects including electron–electron interactions must be taken into account to understand the equilibrium weak topological insulating phase in ZrTe_(5).
基金Project supported by the National Natural Science Foundation of China (Grant Nos.11888101 and U1832202)the Chinese Academy of Sciences (Grant Nos.QYZDB-SSWSLH043,XDB28000000,and XDB33000000)+1 种基金the K.C.Wong Education Foundation (Grant No.GJTD-2018-01)the Informatization Plan of Chinese Academy of Sciences (Grant No.CAS-WX2021SF-0102)。
文摘We report a study of the electronic structure of BaFe_(2)As_(2) under uniaxial strains using angle-resolved photoemission spectroscopy and transport measurements. Two electron bands at the MY point, with an energy splitting of 50 meV in the strain-free sample, shift downward and merge into each other under a large uniaxial strain, while three hole bands at theГ point shift downward together. However, we also observed an enhancement of the resistance anisotropy under uniaxial strains by electrical transport measurements, implying that the applied strains strengthen the electronic nematic order in BaFe_(2)As_(2). These observations suggest that the splitting of these two electron bands at the MY point is not caused by the nematic order in BaFe_(2)As_(2).
文摘The interplay between topology and magnetism is vital for realizing exotic quantum phenomena,significant examples including quantum anomalous Hall effect,axion insulators,and high-order topological states.These states host great potential for future applications in high-speed and low-consumption electronic devices.Despite being extensively investigated,practical platforms are still scarce.In this work,with molecular beam epitaxy(MBE),we provide the first experimental report on high-quality Bi(110)/CrTe_(2) magnetic heterostructure.By employing in-situ high-resolution scanning tunneling microscopy,we are able to examine the interaction between magnetism and topology.There is a potential edge state at an energy level above the Fermi level,but no edge states observed near the Fermi level The absence of high-order topological corner states near EF highlights the importance of lattice matching and interface engineering in designing high-order topological states.Our study provides key insights into the interplay between two-dimensional magnetic and topological materials and offers an important dimension for engineering magnetic topological states.
基金This work is supported by“the Fundamental Research Funds for the Central Universities”,111 project No.B20019Shanghai Natural Science Foundation,grant No.19ZR1466800.
文摘The Jiao Tong University Spectroscopic Telescope(JUST)is a 4.4-meter f/6.0 segmented-mirror telescope dedicated to spectroscopic observations.The JUST primary mirror is composed of 18 hexagonal segments,each with a diameter of 1.1 m.JUST provides two Nasmyth platforms for placing science instruments.One Nasmyth focus fits a field of view of 10′and the other has an extended field of view of 1.2°with correction optics.A tertiary mirror is used to switch between the two Nasmyth foci.JUST will be installed at a site at Lenghu in Qinghai Province,China,and will conduct spectroscopic observations with three types of instruments to explore the dark universe,trace the dynamic universe,and search for exoplanets:(1)a multi-fiber(2000 fibers)medium-resolution spectrometer(R=4000-5000)to spectroscopically map galaxies and large-scale structure;(2)an integral field unit(IFU)array of 500 optical fibers and/or a long-slit spectrograph dedicated to fast follow-ups of transient sources for multi-messenger astronomy;(3)a high-resolution spectrometer(R~100000)designed to identify Jupiter analogs and Earth-like planets,with the capability to characterize the atmospheres of hot exoplanets.
基金the National Postdoctoral Program for Innovative Talents of China(No.BX20220206)。
文摘High-power intense optical sources in the mid-to-long wavelength infrared region are very attractive for a wide range of fields from fundamental research to materials science and biology applications.However,there are still significant challenges in extending long-wavelength infrared pulses into the relativistic regime using conventional optical techniques.Here,based upon a new type of plasma-based optical method,we present an efficient scheme capable of combining several high-power long-wavelength infrared laser pulses into one single,more intense pulse,thus bringing the intensity of the output pulse to the relativistic regime.Such intense infrared pulses will open up new possibilities for strong-field physics and ultrafast applications.Furthermore,this is beneficial to understand the underlying physics and nonlinear processes of modulation,propagation and energy transfer of high-power intense laser pulses in plasmas.
基金the National Natural Science Foundation of China(Grant No.12274126)carried out during the virtual program“Tensor Networks in Many Body and Quantum Field Theory”held at the Institute for Nuclear Theory,University of Washington,Seattle(INT 21–1c)。
文摘Motivated by the mathematical beauty and the recent experimental realizations of fractal systems,we study the spin-1/2 antiferromagnetic Heisenberg model on a Sierpiński gasket.The fractal porous feature generates new kinds of frustration to exhibit exotic quantum states.Using advanced tensor network techniques,we identify a quantum gapless-spin-liquid ground state in fractional spatial dimension.This fractal spin system also demonstrates nontrivial nonlocal properties.While the extremely short-range correlation causes a highly degenerate spin form factor,the entanglement in this fractal system suggests a long-range scaling behavior.We also study the dynamic structure factor and clearly identify the gapless excitation with a stable corner excitation emerged from the ground-state entanglement.Our results unambiguously point out multiple essential properties of this fractal spin system,and open a new route to explore spin liquid and frustrated magnetism.
基金supported in part by the Talent Scientific Start-Up Project of Chinathe National Natural Science Foundation of China(Grant No.12175134)the World Premier International Research Center Initiative(WPI Initiative),MEXT,Japan。
文摘Very high energy(VHE)photons may have a higher survival rate than that expected in standard-model physics,as suggested by the recently reported gamma ray burst GRB221009A.While a photon-axion like particle(ALP)oscillation can boost the survival rate of the VHE photons,current works have not been based on concrete particle models,leaving the identity of the corresponding ALP unclear.Here,we show that the required ALP scenario is consistent with the electroweak axion with an anomaly free Z_(10)Froggatt–Nielsen symmetry.
基金supported by the National SKA program of China(2020SKA0120300)the National Key R&D Program of China(2021YFA0718500)+2 种基金the National Natural Science Foundation of China(grant Nos.11833003,12033001)the China Postdoctoral Science Foundation(No.2023T160410)the Opening Foundation of Xinjiang Key Laboratory(No.2021D04016)。
文摘Black widows(BWs)are millisecond pulsars ablating their companion stars.The out-flowing material from the companion can block the radio emission of the pulsar,resulting in eclipses.In this paper,we construct a model for the radio eclipse by calculating the geometry of the bow shock between the winds of the pulsar and companion,where the shock shapes the eclipsing medium but had not been described in detail in previous works.The model is further used to explain the variations of the flux density and dispersion measure of three BW pulsars(i.e.,PSR B1957+20,J2055+3829,and J2051-0827)detected by the Five-hundred-meter Aperture Spherical radio Telescope.Consequently,we constrained the parameters of the three BW systems such as the inclination angles and true anomalies of the observer as well as the mass-loss rates and wind velocity of the companion stars.With the help of these constraints,it is expected that magnetic fields of companion stars and even masses of pulsars could further be determined as some extra observation can be achieved in the future.
基金supported by the National Natural Science Foundation of China(Grant Nos.11888101 and U1832202)the Chinese Academy of Sciences(Grant Nos.QYZDB-SSW-SLH043,XDB28000000,and XDB33000000)+3 种基金the K.C.Wong Education Foundation(Grant No.GJTD-2018-01)the Informatization Plan of Chinese Academy of Sciences(Grant No.CAS-WX2021SF-0102)supported by the Synergetic Extreme Condition User Facility(SECUF)supported by US DOE(Grant Nos.DESC0010526 and DE-SC0012704)。
文摘We report the observation for the pz electron band and the band inversion in Fe1+yTexSe1-xwith angleresolved photoemission spectroscopy. Furthermore, we found that excess Fe(y>0) inhibits the topological band inversion in Fe1+yTexSe1-x,which explains the absence of Majorana zero modes in previous reports for Fe1+yTexSe1-xwith excess Fe. Based on our analysis of different amounts of Te doping and excess Fe, we propose a delicate topological phase in this material. Thanks to this delicate phase, one may be able to tune the topological transition via applying lattice strain or carrier doping.
基金This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)the National Natural Science Foundation of China(Grant Nos.11991074,11975154,12005287,and 12135009)+2 种基金the Science Challenge Project(Grant No.TZ2018005)X.F.Li was supported by the China and Germany Postdoctoral Exchange Program from the Office of the China Postdoctoral Council and the Helmholtz Centre(Grant No.20191016)and the China Postdoctoral Science Foundation(Grant No.2018M641993)Y.Zhao was also supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011695).Simulations were carried out on the JURECA and JUWELS supercomputers at the Jülich Supercomputing Centre,which are granted from the Projects JZAM04 and LAPIPE.
文摘Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.
基金supported by the National Natural Science Foundation of China (Grant Nos.12174449,12225511,T2241002,12074250,11991073,12135009,61988102,and 61971397)the National Key Research and Development Program of China (Grant Nos.2019YFA0307703 and 2018YFB2202500)。
文摘We report the laser-chirp controlled terahertz(THz) wave generation from two-color-laser-induced air plasma.Our experimental results reveal that the THz wave is affected by both the laser energy and chirp,leading to radiation minima that can be quantitatively reconstructed using the linear-dipole-array model.The phase difference between the two colors,determined by the chirp and intensity of the laser,can account for the radiation minima.Furthermore,we observe an asynchronous variation in the generated THz spectrum,which suggests a THz frequency-dependent phase matching between the laser pulse and THz wave.These results highlight the importance of laser chirp during the THz wave generation and demonstrate the possibility of modulating the THz yields and spectrum through chirping the incident laser pulse.This work can provide valuable insights into the mechanism of plasma-based THz wave generation and offer a unique means to control THz emissions.
基金Project supported by the “Shuguang Program” from Shanghai Education Development Foundation and Shanghai Municipal Education Commission,Ministry of Science and Technology of China(Grant Nos.2016YFA0301003 and 2016YFA0300403)the National Natural Science Foundation of China(Grant Nos.11521404,11634009,11874256,11574202,11874258,11790313,11674226,U1632102,11674222,and 11861161003)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB28000000)
文摘YbMnBi2 is a recently discovered time-reversal-symmetry breaking type-Ⅱ Weyl semimetal.However, as a representation of the new category of topological matters, the scanning tunneling microcopy(STM) results on such important material are still absent.Here, we report the STM investigations on the morphology of vacuum cleaved single crystalline YbMnBi2 samples.A hill and valley type of topography is observed on the YbMnBi2 surface, which is consistent with the non-layer nature of its crystal structure.Analysis of STM images yields the information of the index of the vicinal surface.Our results here lay a playground of future atomic scale research on YbMnBi2.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)the National Natural Science Foundation of China(Grant Nos.11975154,11675108,11655002,and 11775144)+3 种基金the Science Challenge Project(Grant No.TZ2018005)the China Scholarship Council,the China and Germany Postdoctoral Exchange Program from the Office of China Postdoctoral Council and the Helmholtz Centre(Grant No.20191016)the China Postdoctoral Science Foundation(Grant No.2018M641993)funding from the European Union Horizon 2020 Research and Innovation Programme under Grant Agreement No.633053.
文摘Sunlight-like lasers that have a continuous broad frequency spectrum,random phase spectrum,and random polarization are formulated theoretically.With a sunlight-like laser beam consisting of a sequence of temporal speckles,the resonant three-wave coupling that underlies parametric instabilities in laser–plasma interactions can be greatly degraded owing to the limited duration of each speckle and the frequency shift between two adjacent speckles.The wave coupling can be further weakened by the random polarization of such beams.Numerical simulations demonstrate that the intensity threshold of stimulated Raman scattering in homogeneous plasmas can be doubled by using a sunlight-like laser beam with a relative bandwidth of∼1%as compared with a monochromatic laser beam.Consequently,the hot-electron generation harmful to inertial confinement fusion can be effectively controlled by using sunlight-like laser drivers.Such drivers may be realized in the next generation of broadband lasers by combining two or more broadband beams with independent phase spectra or by applying polarization smoothing to a single broadband beam.
文摘In our published letter,[1]we have identified a minor error in Figs.2 and 3.Instead,we have 2111 events in these two plots with 646,249,382,and 834 events in Run 9(20.0 ton·day),Run 10(19.4 ton·day),Run 11–1(24.2 ton·day),and Run 11–2(37.1 ton·day).The mistake is due to an incorrect application of a small energy non-linearity(known as the BLS non-linearity)in making plots,but has no impact to the final results.Figures 2 and 3 are now updated in this note.
基金supported by the National Basic Research Program of China (973 Program, 2015CB857002)the National Natural Science Foundation of China (Grant Nos. 11233005 and 11621303)+3 种基金supported by the High Performance Computing Resource in the Core Facility for Advanced Research Computing at Shanghai Astronomical ObservatoryFunding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundationthe U.S. Department of Energy Office of Sciencesupport and resources from the Center for High-Performance Computing at the University of Utah
文摘Using a sample of galaxies selected from the Sloan Digital Sky Survey Data Release 7(SDSS DR7) and a catalog of bulge-disk decompositions, we study how the size distribution of galaxies depends on the intrinsic properties of galaxies, such as concentration, morphology, specific star formation rate(sSFR),and bulge fraction, and on the large-scale environments in the context of central/satellite decomposition,halo environment, the cosmic web: cluster, filament, sheet and void, as well as galaxy number density. We find that there is a strong dependence of the luminosity-or mass-size relation on the galaxy concentration, morphology, s SFR and bulge fraction. Compared with late-type(spiral) galaxies, there is a clear trend of smaller sizes and steeper slope for early-type(elliptical) galaxies. Similarly, galaxies with a high bulge fraction have smaller sizes and steeper slopes than those with a low bulge fraction. Fitting formulae of the average luminosity-and mass-size relations are provided for galaxies with these different intrinsic properties. Examining galaxies in terms of their large scale environments, we find that the masssize relation has some weak dependence on the halo mass and central/satellite segregation for galaxies within mass range 9.0 ≤ log M*≤ 10.5, where satellites or galaxies in more massive halos have slightly smaller sizes than their counterparts, while the cosmic web and local number density dependence of the mass-size relation is almost negligible.
基金supported by the National Natural Science Foundation of China (NSFC,Grant Nos.11573006,11528306 and 11347163)the Fundamental Research Funds for the Central Universities+1 种基金the Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund (the second phase)the Science and Technology Program Foundation of the Beijing Municipal Commission of Education of China (Grant No.KM201410028003)
文摘We focus on a series of f(R) gravity theories in Palatini formalism to investigate the probabilities of producing late-time acceleration for the flat Friedmann-Robertson-Walker(FRW) universe.We apply a statefinder diagnostic to these cosmological models for chosen series of parameters to see if they can be distinguished from one another. The diagnostic involves the statefinder pair{r,s},where r is derived from the scale factor a and its higher derivatives with respect to the cosmic time t,and s is expressed by r and the deceleration parameter q. In conclusion,we find that although two types of f(R) theories:(i) f(R) = R + αR^m-βR^(-n) and(ii) f(R) = R + α lnR-β can lead to late-time acceleration,their evolutionary trajectories in the r-s and r-q planes reveal different evolutionary properties,which certainly justify the merits of the statefinder diagnostic. Additionally,we utilize the observational Hubble parameter data(OHD) to constrain these models of f(R) gravity. As a result,except for m = n = 1/2 in case(i),α = 0 in case(i) and case(ii) allow the ΛCDM model to exist in the 1σ confidence region. After applying the statefinder diagnostic to the best-fit models,we find that all the best-fit models are capable of going through the deceleration/acceleration transition stage with a late-time acceleration epoch,and all these models turn to the de Sitter point({r,s}={1,0}) in the future. Also,the evolutionary differences between these models are distinct,especially in the r-s plane,which makes the statefinder diagnostic more reliable in discriminating cosmological models.
基金supported by the 973Program(Nos.2015CB857002 and 2015CB857003)the National Natural Science Foundation of China(Grant Nos.11533006,11621303,11833005,11890691 and 11890692)。
文摘Galaxy clustering provides insightful clues to our understanding of galaxy formation and evolution,as well as the universe.The redshift assignment for the random sample is one of the key steps to accurately measure galaxy clustering.In this paper,by virtue of the mock galaxy catalogs,we investigate the effect of two redshift assignment methods on the measurement of galaxy two-point correlation functions(hereafter 2 PCFs),the Vmax method and the"shuffled"method.We have found that the shuffled method significantly underestimates both of the projected 2 PCFs and the two-dimensional 2 PCFs in redshift space,while the Vmax method does not show any notable bias on the 2 PCFs for volume-limited samples.For fluxlimited samples,the bias produced by the Vmax method is less than half of the shuffled method on large scales.Therefore,we strongly recommend the Vmax method to assign redshifts to random samples in the future galaxy clustering analysis.
基金supported by the“trategic Priority Research Program”of the Chinese Academy of Sciences(No.XDA10010800)the National Natural Science Foundation of China(No.12074318)。
文摘To satisfy the accurate positioning requirement of the calibration source in the Jiangmen Underground Neutrino Observatory, a Tonpilz-type hydrophone with low radioactivity and high electroacoustics is developed.The radioactivity of the proposed hydrophone is strictly controlled by selecting pure raw materials, especially active piezoelectric ceramics. The electroacoustic performance of the hydrophone is improved by making structural optimization. High sensitivity and aimed directivity are achieved using 33-mode piezoelectric ceramic rings arranged in series and improvement in the radiating head of the Tonpilz hydrophone, respectively. All electroacoustic performances are studied through finite element analyses.The simulations indicate that the electroacoustic performances of the hydrophones in linear alkylbenzene-based liquid scintillator can be approximately predicted according to the results in water because their differences caused by two types of acoustic media, water and liquid scintillator, are known. The tests show that the hydrophone prototype can achieve a maximum sensitivity of-209.3dB and a beamwidth of 132.2° at a frequency of 143 kHz.In addition, eight hydrophones only contributed to a background radioactivity level of 26 ± 4 mHz in the neutrino analysis.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11521404,12074248,11974243,and 11804194)additional support from a Shanghai talent program。
文摘Using high-resolution angle-resolved and time-resolved photoemission spectroscopy,we have studied the low-energy band structures in occupied and unoccupied states of three ternary compounds GeBi_(2)Te_(4),SnBi_(2)Te_(4) and Sn_(0.571)Bi_(2.286)Se_(4) near the Fermi level.In previously confirmed topological insulator GeBi_(2)Te_(4) compounds,we confirmed the existence of the Dirac surface state and found that the bulk energy gap is much larger than that in the first-principles calculations.In SnBi_(2)Te_(4) compounds,the Dirac surface state was observed,consistent with the first-principles calculations,indicating that it is a topological insulator.The experimental detected bulk gap is a little bit larger than that in calculations.In Sn_(0.571)Bi_(2.286)Se_(4) compounds,our measurements suggest that this nonstoichiometric compound is a topological insulator although the stoichiometric SnBi_(2)Se_(4) compound was proposed to be topological trivial.
基金supported by the National Natural Science Foundation of China(Nos.11833005,11890692 and 11621303)111 project(No.B20019)+1 种基金Shanghai Natural Science Foundation(No.15ZR1446700)the support of the Key Laboratory for Particle Physics,Astrophysics and Cosmology,Ministry of Educationthe Tsung-Dao Lee Institute。
文摘The star formation rate function(SFRF) and specific star formation rate function(s SFRF) from observations are impacted by the Eddington bias, due to uncertainties in the estimated star formation rate(SFR). We develop a novel method to correct the Eddington bias and obtain the intrinsic SFRF and sSFRF from the Sloan Digital Sky Survey(SDSS) Data Release 7. The intrinsic SFRF is in good agreement with measurements from previous data in the literature that relied on UV SFRs but its high star-forming end is slightly lower than the corresponding IR and radio tracers. We demonstrate that the intrinsic sSFRF from SDSS has a bimodal form with one peak found at sSFR ~10-9.7 yr^-1 representing the star-forming objects while the other peak is found at sSFR ~10-12 yr^-1 representing the quenched population. Furthermore, we compare our observations with the predictions from the Illustris TNG and Illustris simulations and affirm that the "TNG" model performs much better than its predecessor. However,we show that the simulated SFRF and CSFRD of TNG simulations are highly dependent on resolution,reflecting the limitations of the model and today’s state-of-the-art simulations. We demonstrate that the bimodal, two peaked s SFRF implied by the SDSS observations does not appear in TNG regardless of the adopted box-size or resolution. This tension reflects the need for inclusion of an additional efficient quenching mechanism in the TNG model.
