Sodium with low cost and high abundance is considered as a substitute element of lithium for batteries and supercapacitors,which need the appropriate host materials to accommodate the relatively large Na^(+) ions.Comp...Sodium with low cost and high abundance is considered as a substitute element of lithium for batteries and supercapacitors,which need the appropriate host materials to accommodate the relatively large Na^(+) ions.Compared to Li^(+) storage,Na^(+) storage makes higher demands on the structural optimization of perovskite bismuth ferrite(BiFeO_(3)).We propose a novel strategy of defect engineering on BiFeO_(3) through Na and V codoping for high-efficiency Na^(+) storage,to reveal the roles of oxygen vacancies and V ions played in the enhanced electrochemical energy storage performances of Na-ion capacitors.The formation of the oxygen vacancies in the Na and V codoped BiFeO_(3)(denoted as NV-BFO),is promoted by Na doping and suppressed by V doping,which can be demonstrated by XPS and EPR spectra.By the first-principles calculations,the oxygen vacancies and V ions in NV-BFO are confirmed to substantially lower the Na^(+)migration energy barriers through the space and electric field effects,to effectively promote the Na^(+) transport in the crystals.Electrochemical kinetic analysis of the NV-BFO//NV-BFO capacitors indicates the dominant capacitive-controlled capacity,which depends on fast Na^(+) deintercalation-intercalation process in the NV-BFO electrode.The NV-BFO//NV-BFO capacitors open up a new avenue for developing highperformance Na-ion capacitors.展开更多
We have systematically investigated the structures of Sr-Ge system under pressures up to 200 GPa and found six stable stoichiometric structures,they being Sr_(3)Ge,Sr_(2)Ge,SrGe,SrGe_(2),SrGe_(3),and SrGe_(4).We demon...We have systematically investigated the structures of Sr-Ge system under pressures up to 200 GPa and found six stable stoichiometric structures,they being Sr_(3)Ge,Sr_(2)Ge,SrGe,SrGe_(2),SrGe_(3),and SrGe_(4).We demonstrate the interesting structure evolution behaviors in Sr-Ge system with the increase of germanium content,Ge atoms arranging into isolated anions in Sr_(3)Ge,chains in Sr_(2) Ge,square units in SrGe,trigonal units and hexahedrons in SrGe_(2),cages in SrGe_(3),hexagons and Geg rings in SrGe_(4).The structural diversity produces various manifestations of electronic structures,which is of benefit to electrical transportation.Among them,these novel phases with metallic structures show superconductivity(maximum T_(c)~8.94 K for Pmmn Sr_(3)Ge).Notably,the n-type semiconducting Pnma SrGe_(2) structure exhibits high Seebeck coefficient and excellent electrical conductivity along the y direction,leading to a high ZT value up to 1.55 at 500 K,which can be potential candidates as high-performance thermoelectrics.Our results will enable the development of fundamental science in condensed matter physics and potential applications in novel electronics or thermoelectric materials.展开更多
Using first-principles calculations, we predict a new type of two-dimensional(2D) boride MB3(M = Be,Ca, Sr), constituted by boron kagome monolayer and the metal atoms adsorbed above the center of the boron hexagons. T...Using first-principles calculations, we predict a new type of two-dimensional(2D) boride MB3(M = Be,Ca, Sr), constituted by boron kagome monolayer and the metal atoms adsorbed above the center of the boron hexagons. The band structures show that the three MB3compounds are metallic, thus the possible phononmediated superconductivity is explored. Based on the Eliashberg equation, for BeB3, CaB3, and SrB3, the calculated electron–phonon coupling constants λ are 0.46, 1.09, and 1.33, and the corresponding superconducting transition temperatures Tc are 3.2, 22.4, and 20.9 K, respectively. To explore superconductivity with higher transition temperature, hydrogenation and charge doping are further considered. The hydrogenated CaB3, i.e.,HCaB3, is stable, with the enhanced λ of 1.39 and a higher Tc of 39.3 K. Moreover, with further hole doping at the concentration of 5.8 × 1011hole/cm2, the Tc of HCaB3can be further increased to 44.2 K, exceeding the Mc Millan limit. The predicted MB3and HCaB3provide new platforms for investigating 2D superconductivity in boron kagome lattice since superconductivity based on monolayer boron kagome lattice has not been studied before.展开更多
The physical mechanism of fast radio bursts(FRBs) is still unknown. On 2020 April 28, a special radio burst, FRB200428, was detected and believed to be associated with the Galactic magnetar SGR 1935+2154. It confirms ...The physical mechanism of fast radio bursts(FRBs) is still unknown. On 2020 April 28, a special radio burst, FRB200428, was detected and believed to be associated with the Galactic magnetar SGR 1935+2154. It confirms that at least some of the FRBs were generated by magnetars, although the radiation mechanism continues to be debated.To this end, we study in detail the multiband afterglows of FRB 200428 described by the synchrotron fireball shock model. We find the prediction for the optical and radio afterglows of FRB 200428 is consistent with the observations when considering the post-FRB optical and radio upper limits from the literature. We also show that the follow up detection of the afterglows from fast radio bursts like—FRB 200428 is possible at the radio band,though challenging. Based on our model, one can obtain information about the energy of the fireball, the radiation zone, and the nature of the surrounding medium. That may shed light on the physical mechanism of FRBs.展开更多
Metal-ion capacitors(including Li^(+),Na^(+),and K^(+))effectively combine a battery negative electrode capable of reversibly intercalating metal cations,together with an electrical double-layer positive electrode.How...Metal-ion capacitors(including Li^(+),Na^(+),and K^(+))effectively combine a battery negative electrode capable of reversibly intercalating metal cations,together with an electrical double-layer positive electrode.However,such novel cell design has a birth defect,namely kinetics mismatch between sluggish negative electrode and fast positive electrode,thus limiting the energy-power performance.Herein,we design a MoS_(2)-carbon composite anode with the ordered macroporous architecture and interlayer-expanded feature,exhibiting the fast and reversible Na^(+)redox processes.This kinetically favored anode is coupled with a homemade activated carbon cathode that allows for the excellent electrochemical performance of sodiumion capacitor with respect to large specific capacity,high-rate capability,and robust cycling.Through quantification of the potential swings of anode and cathode via a three-electrode Swagelok cell,we for the first time observe the abnormal variation law of potential swings and thus directly providing the evidence that the kinetics gap has been filled up by this kinetically favored anode.Our results represent a crucial step toward understanding the key issues of kinetics mismatch for hybrid cell,thus propelling the development of design of kinetically favored anode materials for high-performance metalion capacitors.展开更多
A new kind of non-Gaussian quantum catalyzed state is proposed via multiphoton measurements and two-mode squeezing as an input of thermal state.The characteristics of the generated multiphoton catalysis output state d...A new kind of non-Gaussian quantum catalyzed state is proposed via multiphoton measurements and two-mode squeezing as an input of thermal state.The characteristics of the generated multiphoton catalysis output state depends on the thermal parameter,catalyzed photon number and squeezing parameter.We then analyze the nonclassical properties by examining the photon number distribution,photocount distribution and partial negativity of the Wigner function.Our findings indicate that nonclassicality can be achieved through the implementation of multiphoton catalysis operations and modulated by the thermal parameter,catalyzed photon number and squeezing parameter.展开更多
We study the property of magnetopolaron in a parabolic quantum dot under the Rashba spin–orbit interaction(RSOI)by adopting an unitary transformation of Lee–Low–Pines type and the variational method of Pekar type w...We study the property of magnetopolaron in a parabolic quantum dot under the Rashba spin–orbit interaction(RSOI)by adopting an unitary transformation of Lee–Low–Pines type and the variational method of Pekar type with and without considering the temperature.The temporal spatial distribution of the probability density and the relationships of the oscillating period with the RSOI constant,confinement constant,electron–phonon coupling strength,phonon wave vector and temperature are discussed.The results show that the probability density of the magnetopolaron in the superposition of the ground and first excited state takes periodic oscillation(T0/period)in the presence or absence of temperature.Because of the RSOI,the oscillating period is divided into different branches.Also,the results indicate that the oscillating period increases(decreases)when the RSOI constant,electron-phonon coupling strength and phonon wave vector(the confinement constant)increase in a proper temperature,and the temperature plays a significant role in determining the properties of the polaron.展开更多
A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured thr...A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured through the rotation of scatters. In particular, the band inversion occurs between two pairs of high-order compound states, resulting in topological phase transition from trivial to nontrivial over a relatively broad high-frequency range. This is further evidenced by an effective Hamiltonian derived by the k·p perturbation theory. The phononic topology is related to a pseudo-timereversal symmetry constructed by the point group symmetry of two doubly degenerate eigenstates. Numerical simulations unambiguously demonstrate robust helical edge states whose pseudospin indices are locked to the propagation direction along the interface between topologically trivial and nontrivial phononic crystals. Our designed phononic systems provide potential applications in robust acoustic signal transport along any desired path over a high-frequency range.展开更多
Based on a parabolic coordinate system,we theoretically design and experimentally generate hybridly polarized vector optical fields with parabolic symmetry of the first and second kinds,which can further enrich the fa...Based on a parabolic coordinate system,we theoretically design and experimentally generate hybridly polarized vector optical fields with parabolic symmetry of the first and second kinds,which can further enrich the family of vector optical fields.The wavefront of this new-kind vector optical field contains circular,elliptic and linear polarizations,and the polarizations can keep the same or change along the parabolic curves.Then we present the realization of tunable focal shift with the hybridly polarized vector optical field,and show a specific law of the focal shift of the focused hybridly polarized vector optical field with the parabolic symmetry.We hope these results can provide a new way to flexibly modulate focal fields,which can be applied in realms such as optical machining,optical trapping and information transmission.展开更多
Imaging through fluctuating scattering media such as fog is of challenge since it seriously degrades the image quality.We investigate how the image quality of computational ghost imaging is reduced by fluctuating fog ...Imaging through fluctuating scattering media such as fog is of challenge since it seriously degrades the image quality.We investigate how the image quality of computational ghost imaging is reduced by fluctuating fog and how to obtain a high-quality defogging ghost image. We show theoretically and experimentally that the photon number fluctuations introduced by fluctuating fog is the reason for ghost image degradation. An algorithm is proposed to process the signals collected by the computational ghost imaging device to eliminate photon number fluctuations of different measurement events. Thus, a high-quality defogging ghost image is reconstructed even though fog is evenly distributed on the optical path. A nearly 100% defogging ghost image is obtained by further using a cycle generative adversarial network to process the reconstructed defogging image.展开更多
High pressure and high temperature(HPHT)technology,as an extreme physical condition,plays an important role in regulating the properties of materials,having the advantages of enhancing doping efficiency,refining grain...High pressure and high temperature(HPHT)technology,as an extreme physical condition,plays an important role in regulating the properties of materials,having the advantages of enhancing doping efficiency,refining grain size,and manufacturing defects,therefore it is quite necessary to study the effectiveness on tuning thermoelectric properties.Elemental telluride,a potential candidate for thermoelectric materials,has the poor doping efficiency and high resistivity,which become an obstacle for practical applications.Here,we report the realization of a dual optimization of electrical behaviors and thermal conductivity through HPHT method combining with the introduction of black phosphorus.The results show the maximum zT of 0.65 and an average zT of 0.42(300 K–610 K),which are increased by 55%and 68%in the synthesis pressure regulation system,respectively.This study clarifies that the HPHT method has significant advantages in modulating the thermoelectric parameters,providing a reference for seeking high performance thermoelectric materials.展开更多
The magnetic states of the strongly correlated system plutonium dioxide(PuO_(2)) are studied based on the density functional theory(DFT) plus Hubbard U(DFT +U) method with spin–orbit coupling(SOC) included. A series ...The magnetic states of the strongly correlated system plutonium dioxide(PuO_(2)) are studied based on the density functional theory(DFT) plus Hubbard U(DFT +U) method with spin–orbit coupling(SOC) included. A series of typical magnetic structures including the multiple-k types are simulated and compared in the aspect of atomic structure and total energy. We test LDA, PBE, and SCAN exchange–correlation functionals on PuO_(2) and a longitudinal 3k antiferromagnetic(AFM) ground state is theoretically determined. This magnetic structure has been identified to be the most stable one by the former computational work using the hybrid functional. Our DFT +U + SOC calculations for the longitudinal 3k AFM ground state suggest a direct gap which is in good agreement with the experimental value. In addition, a genetic algorithm is employed and proved to be effective in predicting magnetic ground state of PuO2. Finally, a comparison between the results of two extensively used DFT +U approaches to this system is made.展开更多
The superconductivity of two-dimensional(2D)materials has extremely important research significance.To date,superconducting transition temperatures(T_(c))of 2D superconductors are still far from practical applications...The superconductivity of two-dimensional(2D)materials has extremely important research significance.To date,superconducting transition temperatures(T_(c))of 2D superconductors are still far from practical applications.Previously,2D MXene Mo_(2)N has been successfully synthesized[Urbankowski et al.Nanoscale 917722,(2017)].We systematically investigate the effects of carbonization and further hydrogenation on the stability,electronic property and superconductivity of 1T-and 2H-M_(2)N(M=Mo,W)based on first-principles calculations.The results show that the 1T-M_(2)N and 2H-M_(2)N(M=Mo,W)are all dynamically and thermodynamically stable after carbonization and further hydrogenation.After carbonization,Tc’s of 1T-M_(2)NC_(2)(M=Mo,W)are all increased,while Tc’s of 2H-M_(2)NC_(2)(M=Mo,W)are all decreased.By further hydrogenation,the Tc’s of 1T-and 2H-M_(2)NC2H2are all increased.Among all of these structures,Tcof 1T-Mo_(2)NC_(2)H_(2)is the highest one,reaching 42.7 K,and the corresponding electron-phonon coupling strengthλis 2.27.Therefore,hydrogenation is an effective method to modulate Tc’s of 2D M_(2)NC_(2)(M=Mo,W)materials.展开更多
Research of vortex properties in type-Ⅱsuperconductors is of great importance for potential applications and fundamental physics.Here,we present a comprehensive study of the critical current density Jc,vortex pinning...Research of vortex properties in type-Ⅱsuperconductors is of great importance for potential applications and fundamental physics.Here,we present a comprehensive study of the critical current density Jc,vortex pinning,and phase diagram of Na Cl-type In Te_(1-x)Se_(x)(x=0,0.1,0.2)superconductors synthesized by high-pressure technique.Our studies reveal that the values of Jc calculated by the Bean model exceed 10^(4)A/cm^(2)in the In Te_(1-x)Se_(x)system,signifying good potential for applications.The magnetic hysteresis loops(MHLs)show an asymmetric characteristic at various degrees,which is associated with the surface barrier.Intriguingly,a rare phenomenon in which the second magnetization peak in the MHLs occurs only in the field-descending branch is detected in In Te_(0.9)Se_(0.1).Such an anomalous behavior has not been observed before and can be described by considering the respective roles of the surface barrier and bulk pinning in the field-ascending and field-descending branches.By analyzing the pinning force density versus reduced field,the pinning mechanisms are studied in detail in the framework of the Dew-Hughes model.Finally,combining the results of resistivity and magnetization measurements,the vortex phase diagrams are constructed and discussed.展开更多
As one class of the most important objects in the universe,magnetars can produce a lot of different frequency bursts including X-ray bursts.In Cai et al.,75 X-ray bursts produced by magnetar SGR J1935+2154 during an a...As one class of the most important objects in the universe,magnetars can produce a lot of different frequency bursts including X-ray bursts.In Cai et al.,75 X-ray bursts produced by magnetar SGR J1935+2154 during an active period in 2020 are published,including the duration and net photon counts of each burst,and waiting time based on the trigger time difference.In this paper,we utilize the power-law model,dN(x)/dx∝(x+x_0)~((-α)_x),to fit the cumulative distributions of these parameters.It can be found that all the cumulative distributions can be well fitted,which can be interpreted by a self-organizing criticality theory.Furthermore,we check whether this phenomenon still exists in different energy bands and find that there is no obvious evolution.These findings further confirm that the X-ray bursts from magnetars are likely to be generated by some self-organizing critical process,which can be explained by a possible magnetic reconnection scenario in magnetars.展开更多
Synthesis pressure and structural stability are two crucial factors for highly energetic materials,and recent investigations have indicated that cerium is an efficient catalyst for N2 reduction reactions.Here,we syste...Synthesis pressure and structural stability are two crucial factors for highly energetic materials,and recent investigations have indicated that cerium is an efficient catalyst for N2 reduction reactions.Here,we systematically explore Ce–N compounds through first-principles calculations,demonstrating that the cerium atom can weaken the strength of the N≡N bond and that a rich variety of cerium polynitrides can be formed under moderate pressure.Significantly,P1-CeN_(6) possesses the lowest synthesis pressure of 32 GPa among layered metal polynitrides owing to the strong ligand effect of cerium.The layered structure of P1-CeN_(6) proposed here consists of novel N_(14) ring.To clarify the formation mechanism of P1-CeN_(6),the reaction path Ce+3N2→trans-CeN_(6)→P1-CeN_(6) is proposed.In addition,P1-CeN_(6) possesses high hardness(20.73 GPa)and can be quenched to ambient conditions.Charge transfer between cerium atoms and N_(14) rings plays a crucial role in structural stability.Furthermore,the volumetric energy density(11.20 kJ/cm^(3))of P1-CeN_(6) is much larger than that of TNT(7.05 kJ/cm^(3)),and its detonation pressure(128.95 GPa)and detonation velocity(13.60 km/s)are respectively about seven times and twice those of TNT,and it is therefore a promising high-energy-density material.展开更多
A 200-second X-ray quasi-periodicity in the 2-8 ke V band from Swift J1644+57 was found by Reis et al.From the onset time of quasi-periodic oscillation(QPO),we show that Swift J1644+57 is a plunging event.This QPO may...A 200-second X-ray quasi-periodicity in the 2-8 ke V band from Swift J1644+57 was found by Reis et al.From the onset time of quasi-periodic oscillation(QPO),we show that Swift J1644+57 is a plunging event.This QPO may be related to discrete clumps from the accretion disk falling into a supermassive black hole,then the outflow in the jet may be also discontinuous.We estimate the lifetime of clumps to be about several hundreds seconds and the fraction of clumpy ejecta to be about 30% from the QPO.The other possible model involves the interface between the inflow and jet magnetosphere in the magnetically choked accretion flow.Theory and numerical simulations indicate that a magnetic Rayleigh-Taylor and Kelvin-Helmholtz unstable magnetospheric interface can produce a jet-disk QPO mechanism.This event may be the first evidence of jet-disk QPO.From observations,the two models are comparable.展开更多
This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the su...This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.展开更多
Two new photon-modulated spin coherent states(SCSs)are introduced by operating the spin ladder operators J±on the ordinary SCS in the Holstein-Primakoff realization and the nonclassicality is exhibited via their ...Two new photon-modulated spin coherent states(SCSs)are introduced by operating the spin ladder operators J±on the ordinary SCS in the Holstein-Primakoff realization and the nonclassicality is exhibited via their photon number distribution,second-order correlation function,photocount distribution and negativity of Wigner distribution.Analytical results show that the photocount distribution is a Bernoulli distribution and the Wigner functions are only associated with two-variable Hermite polynomials.Compared with the ordinary SCS,the photon-modulated SCSs exhibit more stronger nonclassicality in certain regions of the photon modulated number k and spin number j,which means that the nonclassicality can be enhanced by selecting suitable parameters.展开更多
New stable stoichiometries in K-Ga systems are firstly investigated up to 100 GPa by the unbiased structure searching techniques.Six novel compositions as K4Ga,K3Ga,K2Ga,KGa,KGa2 and KGa4 are found to be thermodynamic...New stable stoichiometries in K-Ga systems are firstly investigated up to 100 GPa by the unbiased structure searching techniques.Six novel compositions as K4Ga,K3Ga,K2Ga,KGa,KGa2 and KGa4 are found to be thermodynamically stable under pressure.Most of the predicted stable phases exhibit metallic character,while the Fd3m KGa phase behaves as a semiconductor with a bandgap ~1.62 eV.Notably,the gallium atoms exhibit different interesting morphologies;e.g.,Ga2 units,zigzag chains,six rings and cage.We further investigate the bonding nature of K-Ga systems with help of electron localization function and Bader charge analyses.Strong covalent bonding characteristics are found between the Ga and Ga atoms,and ionic bonding patterns are observed between the K and Ga atoms.Meanwhile,we notice charge transferring from the K atom to the Ga atom in the K-Ga systems.The present results can be helpful for understanding the diverse structures and properties of K-Ga binary compounds at high pressures.展开更多
基金financial supports from National Natural Science Foundation of China(22005174 and 52271133)。
文摘Sodium with low cost and high abundance is considered as a substitute element of lithium for batteries and supercapacitors,which need the appropriate host materials to accommodate the relatively large Na^(+) ions.Compared to Li^(+) storage,Na^(+) storage makes higher demands on the structural optimization of perovskite bismuth ferrite(BiFeO_(3)).We propose a novel strategy of defect engineering on BiFeO_(3) through Na and V codoping for high-efficiency Na^(+) storage,to reveal the roles of oxygen vacancies and V ions played in the enhanced electrochemical energy storage performances of Na-ion capacitors.The formation of the oxygen vacancies in the Na and V codoped BiFeO_(3)(denoted as NV-BFO),is promoted by Na doping and suppressed by V doping,which can be demonstrated by XPS and EPR spectra.By the first-principles calculations,the oxygen vacancies and V ions in NV-BFO are confirmed to substantially lower the Na^(+)migration energy barriers through the space and electric field effects,to effectively promote the Na^(+) transport in the crystals.Electrochemical kinetic analysis of the NV-BFO//NV-BFO capacitors indicates the dominant capacitive-controlled capacity,which depends on fast Na^(+) deintercalation-intercalation process in the NV-BFO electrode.The NV-BFO//NV-BFO capacitors open up a new avenue for developing highperformance Na-ion capacitors.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.52102335,11704220,11804184,11974208,and 11804185)the Shandong Provincial Natural Science Foundation,China (Grant Nos.ZR2021MA050,ZR2017BA020,ZR2018PA010,ZR2019MA054,and ZR2017BA012)。
文摘We have systematically investigated the structures of Sr-Ge system under pressures up to 200 GPa and found six stable stoichiometric structures,they being Sr_(3)Ge,Sr_(2)Ge,SrGe,SrGe_(2),SrGe_(3),and SrGe_(4).We demonstrate the interesting structure evolution behaviors in Sr-Ge system with the increase of germanium content,Ge atoms arranging into isolated anions in Sr_(3)Ge,chains in Sr_(2) Ge,square units in SrGe,trigonal units and hexahedrons in SrGe_(2),cages in SrGe_(3),hexagons and Geg rings in SrGe_(4).The structural diversity produces various manifestations of electronic structures,which is of benefit to electrical transportation.Among them,these novel phases with metallic structures show superconductivity(maximum T_(c)~8.94 K for Pmmn Sr_(3)Ge).Notably,the n-type semiconducting Pnma SrGe_(2) structure exhibits high Seebeck coefficient and excellent electrical conductivity along the y direction,leading to a high ZT value up to 1.55 at 500 K,which can be potential candidates as high-performance thermoelectrics.Our results will enable the development of fundamental science in condensed matter physics and potential applications in novel electronics or thermoelectric materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074213,11574108,and 12104253)the Major Basic Program of Natural Science Foundation of Shandong Province(Grant No.ZR2021ZD01)+1 种基金the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Provincethe Texas Center for Superconductivity at University of Houston,the Robert A.Welch Foundation(Grant No.E-1146)。
文摘Using first-principles calculations, we predict a new type of two-dimensional(2D) boride MB3(M = Be,Ca, Sr), constituted by boron kagome monolayer and the metal atoms adsorbed above the center of the boron hexagons. The band structures show that the three MB3compounds are metallic, thus the possible phononmediated superconductivity is explored. Based on the Eliashberg equation, for BeB3, CaB3, and SrB3, the calculated electron–phonon coupling constants λ are 0.46, 1.09, and 1.33, and the corresponding superconducting transition temperatures Tc are 3.2, 22.4, and 20.9 K, respectively. To explore superconductivity with higher transition temperature, hydrogenation and charge doping are further considered. The hydrogenated CaB3, i.e.,HCaB3, is stable, with the enhanced λ of 1.39 and a higher Tc of 39.3 K. Moreover, with further hole doping at the concentration of 5.8 × 1011hole/cm2, the Tc of HCaB3can be further increased to 44.2 K, exceeding the Mc Millan limit. The predicted MB3and HCaB3provide new platforms for investigating 2D superconductivity in boron kagome lattice since superconductivity based on monolayer boron kagome lattice has not been studied before.
基金supported by the National Natural Science Foundation of China (grant No. U2038106)China Manned Spaced Project (CMS-CSST-2021-A12)+1 种基金supported by the National Natural Science Foundation of China(grant No. 12203013)the Guangxi Science Foundation(grant Nos. AD22035171 and 2023GXNSFBA026030)。
文摘The physical mechanism of fast radio bursts(FRBs) is still unknown. On 2020 April 28, a special radio burst, FRB200428, was detected and believed to be associated with the Galactic magnetar SGR 1935+2154. It confirms that at least some of the FRBs were generated by magnetars, although the radiation mechanism continues to be debated.To this end, we study in detail the multiband afterglows of FRB 200428 described by the synchrotron fireball shock model. We find the prediction for the optical and radio afterglows of FRB 200428 is consistent with the observations when considering the post-FRB optical and radio upper limits from the literature. We also show that the follow up detection of the afterglows from fast radio bursts like—FRB 200428 is possible at the radio band,though challenging. Based on our model, one can obtain information about the energy of the fireball, the radiation zone, and the nature of the surrounding medium. That may shed light on the physical mechanism of FRBs.
基金supported by National Natural Science Foundation of China(No.51902188)Natural Science Foundation of Jiangsu Province(No.BK20190207)+1 种基金Natural Science Doctoral Foundation of Shandong Province(No.ZR2019BB057)the CAS Key Laboratory of Carbon Materials(No.KLCMKFJJ2006).
文摘Metal-ion capacitors(including Li^(+),Na^(+),and K^(+))effectively combine a battery negative electrode capable of reversibly intercalating metal cations,together with an electrical double-layer positive electrode.However,such novel cell design has a birth defect,namely kinetics mismatch between sluggish negative electrode and fast positive electrode,thus limiting the energy-power performance.Herein,we design a MoS_(2)-carbon composite anode with the ordered macroporous architecture and interlayer-expanded feature,exhibiting the fast and reversible Na^(+)redox processes.This kinetically favored anode is coupled with a homemade activated carbon cathode that allows for the excellent electrochemical performance of sodiumion capacitor with respect to large specific capacity,high-rate capability,and robust cycling.Through quantification of the potential swings of anode and cathode via a three-electrode Swagelok cell,we for the first time observe the abnormal variation law of potential swings and thus directly providing the evidence that the kinetics gap has been filled up by this kinetically favored anode.Our results represent a crucial step toward understanding the key issues of kinetics mismatch for hybrid cell,thus propelling the development of design of kinetically favored anode materials for high-performance metalion capacitors.
基金supported by the National Natural Science Foundation of China (Grant No.11347026)the Natural Science Foundation of Shandong Province,China (Grant Nos.ZR2020MA085 and ZR2020MF113)。
文摘A new kind of non-Gaussian quantum catalyzed state is proposed via multiphoton measurements and two-mode squeezing as an input of thermal state.The characteristics of the generated multiphoton catalysis output state depends on the thermal parameter,catalyzed photon number and squeezing parameter.We then analyze the nonclassical properties by examining the photon number distribution,photocount distribution and partial negativity of the Wigner function.Our findings indicate that nonclassicality can be achieved through the implementation of multiphoton catalysis operations and modulated by the thermal parameter,catalyzed photon number and squeezing parameter.
基金Project supported by the National Natural Science Foundation of China(Grant No.11975011).
文摘We study the property of magnetopolaron in a parabolic quantum dot under the Rashba spin–orbit interaction(RSOI)by adopting an unitary transformation of Lee–Low–Pines type and the variational method of Pekar type with and without considering the temperature.The temporal spatial distribution of the probability density and the relationships of the oscillating period with the RSOI constant,confinement constant,electron–phonon coupling strength,phonon wave vector and temperature are discussed.The results show that the probability density of the magnetopolaron in the superposition of the ground and first excited state takes periodic oscillation(T0/period)in the presence or absence of temperature.Because of the RSOI,the oscillating period is divided into different branches.Also,the results indicate that the oscillating period increases(decreases)when the RSOI constant,electron-phonon coupling strength and phonon wave vector(the confinement constant)increase in a proper temperature,and the temperature plays a significant role in determining the properties of the polaron.
基金Project supported by the Young Scientists Fund of the Natural Science Foundation of Shandong Province,China(Grant No.ZR2016AQ09)Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11704219).
文摘A simple two-dimensional phononic crystal hosting topologically protected edge states is proposed to emulate the quantum spin Hall effect in electronic systems, whose phononic topological phase can be reconfigured through the rotation of scatters. In particular, the band inversion occurs between two pairs of high-order compound states, resulting in topological phase transition from trivial to nontrivial over a relatively broad high-frequency range. This is further evidenced by an effective Hamiltonian derived by the k·p perturbation theory. The phononic topology is related to a pseudo-timereversal symmetry constructed by the point group symmetry of two doubly degenerate eigenstates. Numerical simulations unambiguously demonstrate robust helical edge states whose pseudospin indices are locked to the propagation direction along the interface between topologically trivial and nontrivial phononic crystals. Our designed phononic systems provide potential applications in robust acoustic signal transport along any desired path over a high-frequency range.
基金the National Natural Science Foundation of China(Grant Nos.11534006,11674184,11774183,11804187 and 11904199)the Natural Science Foundation of Shandong Province(Grant No.ZR2019BF006)the Collaborative Innovation Center of Extreme Optics。
文摘Based on a parabolic coordinate system,we theoretically design and experimentally generate hybridly polarized vector optical fields with parabolic symmetry of the first and second kinds,which can further enrich the family of vector optical fields.The wavefront of this new-kind vector optical field contains circular,elliptic and linear polarizations,and the polarizations can keep the same or change along the parabolic curves.Then we present the realization of tunable focal shift with the hybridly polarized vector optical field,and show a specific law of the focal shift of the focused hybridly polarized vector optical field with the parabolic symmetry.We hope these results can provide a new way to flexibly modulate focal fields,which can be applied in realms such as optical machining,optical trapping and information transmission.
基金supported by the Natural Science Foundation of Shandong Province, China (Grant No. ZR2022MF249)。
文摘Imaging through fluctuating scattering media such as fog is of challenge since it seriously degrades the image quality.We investigate how the image quality of computational ghost imaging is reduced by fluctuating fog and how to obtain a high-quality defogging ghost image. We show theoretically and experimentally that the photon number fluctuations introduced by fluctuating fog is the reason for ghost image degradation. An algorithm is proposed to process the signals collected by the computational ghost imaging device to eliminate photon number fluctuations of different measurement events. Thus, a high-quality defogging ghost image is reconstructed even though fog is evenly distributed on the optical path. A nearly 100% defogging ghost image is obtained by further using a cycle generative adversarial network to process the reconstructed defogging image.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11804185,11974208,52172212,52102335,and 52002217)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2020YQ05,ZR2019MA054,2019KJJ020,ZR2021YQ03,and 2022KJA043)。
文摘High pressure and high temperature(HPHT)technology,as an extreme physical condition,plays an important role in regulating the properties of materials,having the advantages of enhancing doping efficiency,refining grain size,and manufacturing defects,therefore it is quite necessary to study the effectiveness on tuning thermoelectric properties.Elemental telluride,a potential candidate for thermoelectric materials,has the poor doping efficiency and high resistivity,which become an obstacle for practical applications.Here,we report the realization of a dual optimization of electrical behaviors and thermal conductivity through HPHT method combining with the introduction of black phosphorus.The results show the maximum zT of 0.65 and an average zT of 0.42(300 K–610 K),which are increased by 55%and 68%in the synthesis pressure regulation system,respectively.This study clarifies that the HPHT method has significant advantages in modulating the thermoelectric parameters,providing a reference for seeking high performance thermoelectric materials.
基金supported by National Natural Science Foundation of China, (Grant No. 12104034)。
文摘The magnetic states of the strongly correlated system plutonium dioxide(PuO_(2)) are studied based on the density functional theory(DFT) plus Hubbard U(DFT +U) method with spin–orbit coupling(SOC) included. A series of typical magnetic structures including the multiple-k types are simulated and compared in the aspect of atomic structure and total energy. We test LDA, PBE, and SCAN exchange–correlation functionals on PuO_(2) and a longitudinal 3k antiferromagnetic(AFM) ground state is theoretically determined. This magnetic structure has been identified to be the most stable one by the former computational work using the hybrid functional. Our DFT +U + SOC calculations for the longitudinal 3k AFM ground state suggest a direct gap which is in good agreement with the experimental value. In addition, a genetic algorithm is employed and proved to be effective in predicting magnetic ground state of PuO2. Finally, a comparison between the results of two extensively used DFT +U approaches to this system is made.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074213,11574108,and 12104253)the Major Basic Program of Natural Science Foundation of Shandong Province(Grant No.ZR2021ZD01)+3 种基金the Natural Science Foundation of Shandong Provincial(Grant No.ZR2023MA082)the Project of Introduction and Cultivation for Young Innovative Talents in Colleges and Universities of Shandong Provincethe Texas Center for Superconductivity at University of Houstonthe Robert A.Welch Foundation(Grant No.E-1146)。
文摘The superconductivity of two-dimensional(2D)materials has extremely important research significance.To date,superconducting transition temperatures(T_(c))of 2D superconductors are still far from practical applications.Previously,2D MXene Mo_(2)N has been successfully synthesized[Urbankowski et al.Nanoscale 917722,(2017)].We systematically investigate the effects of carbonization and further hydrogenation on the stability,electronic property and superconductivity of 1T-and 2H-M_(2)N(M=Mo,W)based on first-principles calculations.The results show that the 1T-M_(2)N and 2H-M_(2)N(M=Mo,W)are all dynamically and thermodynamically stable after carbonization and further hydrogenation.After carbonization,Tc’s of 1T-M_(2)NC_(2)(M=Mo,W)are all increased,while Tc’s of 2H-M_(2)NC_(2)(M=Mo,W)are all decreased.By further hydrogenation,the Tc’s of 1T-and 2H-M_(2)NC2H2are all increased.Among all of these structures,Tcof 1T-Mo_(2)NC_(2)H_(2)is the highest one,reaching 42.7 K,and the corresponding electron-phonon coupling strengthλis 2.27.Therefore,hydrogenation is an effective method to modulate Tc’s of 2D M_(2)NC_(2)(M=Mo,W)materials.
基金the National Natural Science Foundation of China(Grant Nos.12204265 and 12204487)the Natural Science Foundation of Shandong Province(Grant Nos.ZR2022QA040,2022KJ183,and 2019KJJ020)+1 种基金the National Key R&D Program of China(Grant No.2018YFA0704300)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)。
文摘Research of vortex properties in type-Ⅱsuperconductors is of great importance for potential applications and fundamental physics.Here,we present a comprehensive study of the critical current density Jc,vortex pinning,and phase diagram of Na Cl-type In Te_(1-x)Se_(x)(x=0,0.1,0.2)superconductors synthesized by high-pressure technique.Our studies reveal that the values of Jc calculated by the Bean model exceed 10^(4)A/cm^(2)in the In Te_(1-x)Se_(x)system,signifying good potential for applications.The magnetic hysteresis loops(MHLs)show an asymmetric characteristic at various degrees,which is associated with the surface barrier.Intriguingly,a rare phenomenon in which the second magnetization peak in the MHLs occurs only in the field-descending branch is detected in In Te_(0.9)Se_(0.1).Such an anomalous behavior has not been observed before and can be described by considering the respective roles of the surface barrier and bulk pinning in the field-ascending and field-descending branches.By analyzing the pinning force density versus reduced field,the pinning mechanisms are studied in detail in the framework of the Dew-Hughes model.Finally,combining the results of resistivity and magnetization measurements,the vortex phase diagrams are constructed and discussed.
基金supported by the National Key R&D Program of China(2021YFA0718500)the National Natural Science Foundation of China under grants U2038106 and 12065017partially by the Jiangxi Provincial Natural Science Foundation under grant 20224ACB211001。
文摘As one class of the most important objects in the universe,magnetars can produce a lot of different frequency bursts including X-ray bursts.In Cai et al.,75 X-ray bursts produced by magnetar SGR J1935+2154 during an active period in 2020 are published,including the duration and net photon counts of each burst,and waiting time based on the trigger time difference.In this paper,we utilize the power-law model,dN(x)/dx∝(x+x_0)~((-α)_x),to fit the cumulative distributions of these parameters.It can be found that all the cumulative distributions can be well fitted,which can be interpreted by a self-organizing criticality theory.Furthermore,we check whether this phenomenon still exists in different energy bands and find that there is no obvious evolution.These findings further confirm that the X-ray bursts from magnetars are likely to be generated by some self-organizing critical process,which can be explained by a possible magnetic reconnection scenario in magnetars.
基金This work was supported financially by the National Key R&D Program of China(Grant Nos.2018YFA0305900 and 2018YFA0703404)the National Natural Science Foundation of China under Grant Nos.21905159,11634004,51320105007,11604116,and 51602124,the Program for Changjiang Scholars and Innovative Research Team in the University of the Ministry of Education of China under Grant No.IRT1132+1 种基金the Higher Educational Youth Innovation Science and Technology Program Shandong Province(Grant No.2022KJ183)GHfund B(Grant No.202202026143).
文摘Synthesis pressure and structural stability are two crucial factors for highly energetic materials,and recent investigations have indicated that cerium is an efficient catalyst for N2 reduction reactions.Here,we systematically explore Ce–N compounds through first-principles calculations,demonstrating that the cerium atom can weaken the strength of the N≡N bond and that a rich variety of cerium polynitrides can be formed under moderate pressure.Significantly,P1-CeN_(6) possesses the lowest synthesis pressure of 32 GPa among layered metal polynitrides owing to the strong ligand effect of cerium.The layered structure of P1-CeN_(6) proposed here consists of novel N_(14) ring.To clarify the formation mechanism of P1-CeN_(6),the reaction path Ce+3N2→trans-CeN_(6)→P1-CeN_(6) is proposed.In addition,P1-CeN_(6) possesses high hardness(20.73 GPa)and can be quenched to ambient conditions.Charge transfer between cerium atoms and N_(14) rings plays a crucial role in structural stability.Furthermore,the volumetric energy density(11.20 kJ/cm^(3))of P1-CeN_(6) is much larger than that of TNT(7.05 kJ/cm^(3)),and its detonation pressure(128.95 GPa)and detonation velocity(13.60 km/s)are respectively about seven times and twice those of TNT,and it is therefore a promising high-energy-density material.
基金supported by the National Natural Science Foundation of China(Grant Nos.11504199,11703015 and U1831207)the China Postdoctoral Science Foundation(Grant No.2017M612233)+1 种基金the Natural Science Foundation of Shandong Province(Grant Nos.ZR2015AM004 and ZR2017BA006)Technology Program of Qufu Normal University(xkj201614)
文摘A 200-second X-ray quasi-periodicity in the 2-8 ke V band from Swift J1644+57 was found by Reis et al.From the onset time of quasi-periodic oscillation(QPO),we show that Swift J1644+57 is a plunging event.This QPO may be related to discrete clumps from the accretion disk falling into a supermassive black hole,then the outflow in the jet may be also discontinuous.We estimate the lifetime of clumps to be about several hundreds seconds and the fraction of clumpy ejecta to be about 30% from the QPO.The other possible model involves the interface between the inflow and jet magnetosphere in the magnetically choked accretion flow.Theory and numerical simulations indicate that a magnetic Rayleigh-Taylor and Kelvin-Helmholtz unstable magnetospheric interface can produce a jet-disk QPO mechanism.This event may be the first evidence of jet-disk QPO.From observations,the two models are comparable.
基金Project supported by the National Youth Foundation of China(Grant Nos.11904200 and 11704219)the National Natural Science Foundation of China(Grant No.11774053)+3 种基金the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20190726)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(Grant No.18KJD140004)NJUPT-SF(Grant No.NY218099)the Opening Project of the Shanghai Key Laboratory of Special Artificial Microstructure Materials and Technology(Grant No.hxkj2019007).
文摘This study proposes a bi-layer windmill-shaped metamaterial that consists of resonators, with similar shapes, on both sides of a dielectric substrate. In this study, the second layer is rotated clockwise around the substrate normal at 90°and thereafter flipped in the first layer. Due to the introduction of a windmill-like shape, the resonant structures result in new resonant modes and thus can achieve multi-band high-efficiency cross-polarization conversions and asymmetric transmissions(ATs) for a linearly polarized incident plane wave with a maximum asymmetric parameter of 0.72. Depending on the geometric parameters of our windmill-shaped structures, the AT effects can be flexibly modulated in a broad multiband from 160 THz to 400 THz, which has not been reported in previous studies. These outstanding AT effects provide potential applications in optical diodes, polarization control switches, and other nano-devices.
基金supported by the National Natural Science Foundation of China(Grant No.11347026)the Natural Science Foundation of Shandong Province,China(Grant Nos.ZR2020MA085 and ZR2020MF113)。
文摘Two new photon-modulated spin coherent states(SCSs)are introduced by operating the spin ladder operators J±on the ordinary SCS in the Holstein-Primakoff realization and the nonclassicality is exhibited via their photon number distribution,second-order correlation function,photocount distribution and negativity of Wigner distribution.Analytical results show that the photocount distribution is a Bernoulli distribution and the Wigner functions are only associated with two-variable Hermite polynomials.Compared with the ordinary SCS,the photon-modulated SCSs exhibit more stronger nonclassicality in certain regions of the photon modulated number k and spin number j,which means that the nonclassicality can be enhanced by selecting suitable parameters.
基金the Shandong-Provincial Science Foundation(ZR2018PA010,ZR2017BA020,ZR2017BA012,ZR2019MA054 and 2019KJJ020)the National Natural Science Foundation of China(11704220,11674122,11804184,1180418 and 11974208).
文摘New stable stoichiometries in K-Ga systems are firstly investigated up to 100 GPa by the unbiased structure searching techniques.Six novel compositions as K4Ga,K3Ga,K2Ga,KGa,KGa2 and KGa4 are found to be thermodynamically stable under pressure.Most of the predicted stable phases exhibit metallic character,while the Fd3m KGa phase behaves as a semiconductor with a bandgap ~1.62 eV.Notably,the gallium atoms exhibit different interesting morphologies;e.g.,Ga2 units,zigzag chains,six rings and cage.We further investigate the bonding nature of K-Ga systems with help of electron localization function and Bader charge analyses.Strong covalent bonding characteristics are found between the Ga and Ga atoms,and ionic bonding patterns are observed between the K and Ga atoms.Meanwhile,we notice charge transferring from the K atom to the Ga atom in the K-Ga systems.The present results can be helpful for understanding the diverse structures and properties of K-Ga binary compounds at high pressures.
