Erbium-doped lithium niobate(LN)on insulator active devices,such as lasers and amplifiers,have received increasing attention.The nonlinear optical oscillation in them at high power destabilizes the output of signals a...Erbium-doped lithium niobate(LN)on insulator active devices,such as lasers and amplifiers,have received increasing attention.The nonlinear optical oscillation in them at high power destabilizes the output of signals and cannot be ignored.In this study,we reported the experimental observation and theoretical analysis of the nonlinear optical oscillation in erbiumdoped lithium niobate-on-insulator(LNOI)microring resonators while scanning the pump wavelength.Under the same pump power,the number of oscillation cycles decreases when the wavelength scanning rate increases from 10.6 to 33.9 nm/μs.A theoretical model based on the competition between the thermo-optic nonlinearity and the photorefractive effect was introduced to interpret the oscillation in transmission.A series of parameters were obtained from the comparison between the theoretical and experimental results;some of them,the relaxation rates of the thermal and the electric field,are significantly different from those of undoped LNOI microcavities.This work provides a valuable reference for future applications of active LNOI devices.展开更多
Viscosity is a crucial dynamic property for alloy liquids.For alloy liquids with glass-forming ability,their viscosity undergoes a change of more than ten orders of magnitude upon cooling,and eventually,a transition f...Viscosity is a crucial dynamic property for alloy liquids.For alloy liquids with glass-forming ability,their viscosity undergoes a change of more than ten orders of magnitude upon cooling,and eventually,a transition from liquid to glassy state occurs when viscosity reaches 1012 Pa s.Nevertheless,the viscosity measurement in the supercooled liquid region(SLR)has been an experimental challenge.Here,in this work,by combining conventional and fast scanning calorimeters,the accurate viscosity of supercooled liquids for Au_(49)Ag_(5.5)Pd_(2.3)Cu_(26.9)Si_(16.3) and Zr_(44)Ti_(11)Cu_(10)Ni_(10)Be_(25) metallic glasses(MGs)was measured over a wide viscosity range of 10^(6)-10^(12) Pa s.Moreover,the viscosity range of 10^(6)-10^(8) Pa s is generally selected for thermoplastic forming(TPF),which takes advantage of the dramatic softening that MGs exhibit after being heated into the SLR.We further gave the TPF process window covering the range of processing temperature and time by utilizing the obtained viscosity data and timetemperature-transformation curves.The optimal time window avoiding property degradation was also determined,based on that there was no marked effect on the mechanical properties of MGs when crystallinity was below~5%.Our findings not only provide the accurate viscosity data in the SLR,but also determine the optimal process parameters for the TPF process.展开更多
We investigated the critical dynamical scalarization and descalarization of black holes within the framework of the EinsteinMaxwell-scalar theory featuring higher-order coupling functions.Both the critical scalarizati...We investigated the critical dynamical scalarization and descalarization of black holes within the framework of the EinsteinMaxwell-scalar theory featuring higher-order coupling functions.Both the critical scalarization and descalarization displayed first-order phase transitions.When examining the nonlinear dynamics near the threshold,we always observed critical solutions that are linearly unstable static scalarized black holes.The critical dynamical scalarization and descalarization share certain similarities with the typeⅠcritical gravitational collapse.However,their initial configurations,critical solutions,and final outcomes differ significantly.To provide further insights into the dynamical results,we conducted a comparative analysis involving static solutions and perturbative analysis.展开更多
Strong interaction is believed to be described by a theory called Quantum Chromodynamics(QCD),an important sector of the Standard Model(SM)of particle physics.QCD is a strange and charming theory,just like the two nam...Strong interaction is believed to be described by a theory called Quantum Chromodynamics(QCD),an important sector of the Standard Model(SM)of particle physics.QCD is a strange and charming theory,just like the two names of its building blocks suggest and remains to be the least wellunderstood part of the SM.展开更多
In this study,we investigate the quasinormal modes(QNMs)of a Lorentz-violating spacetime,factoring in a cosmological constant,within the framework of Einstein-bumblebee gravity.Our findings reveal that the interaction...In this study,we investigate the quasinormal modes(QNMs)of a Lorentz-violating spacetime,factoring in a cosmological constant,within the framework of Einstein-bumblebee gravity.Our findings reveal that the interaction of spacetime with an anisotropic bumblebee field imparts distinct contributions to the axial and polar sectors of the vector perturbations.This subsequently breaks the isospectrality typically observed in vector modes.Numerical evidence strongly indicates isospectral breaking in the vector modes of Einstein-bumblebee black holes:a pronounced breakage in the real part of the frequencies,while the imaginary component seems less affected.This isospectral breaking indicates the existence of two different waveforms in the Ringdown phase of the black hole,which provides a potential signal of quantum gravity observable in current experiments.展开更多
Non-Hermitian systems featuring exceptional points(EPs)or spectral coalescences of eigenvalues and eigenfunctions have led to many surprisingly important applications, such as single-mode lasing, loss-induced transpar...Non-Hermitian systems featuring exceptional points(EPs)or spectral coalescences of eigenvalues and eigenfunctions have led to many surprisingly important applications, such as single-mode lasing, loss-induced transparency, and highprecision metrology. However, most previous demonstrations of EPs have necessitated at least two coupled modes,thereby limiting the achievement and utilization of EPs in a wide range of single-mode systems.展开更多
Quantum systems that undergo quantum phase transitions exhibit divergent susceptibility and can be exploited as probes to estimate physical parameters.We generalize the dynamic framework for criticality-enhanced quant...Quantum systems that undergo quantum phase transitions exhibit divergent susceptibility and can be exploited as probes to estimate physical parameters.We generalize the dynamic framework for criticality-enhanced quantum sensing by the quantum Rabi model(QRM)to its anisotropic counterpart and derive the correspondingly analytical expressions for the quantum Fisher information(QFI).We find that the contributions of the rotating-wave and counterrotating-wave interaction terms are symmetric at the limit of the infinite ratio of qubit frequency to field frequency,with the QFI reaching a maximum for the isotropic QRM.At finite frequency scaling,we analytically derive the inverted variance of higher-order correction and find that it is more affected by the rotating-wave coupling than by the counterrotating-wave coupling.展开更多
Using the attractive Hubbard model as an example,we theoretically investigate the gap function,superfluid density,and superconductivity(SC)transition temperature on the semiperiodic Penrose lattice.First,we clarify th...Using the attractive Hubbard model as an example,we theoretically investigate the gap function,superfluid density,and superconductivity(SC)transition temperature on the semiperiodic Penrose lattice.First,we clarify that the gap function,density of states,and superfluid density positively correlate to the extended degree of single-particle states around the Fermi energy.Second,we confirm that the paramagnetic component of the superfluid density does not decay to zero in the thermodynamic limit,which is completely diferent from periodic systems.Regardless of the scaling,the diference between diamagnetic and paramagnetic currents remains stable,consistent with recent experimental results showing that although the superfluid density is lower than that of a periodic system,the system has bulk SC.Third,we find that the superfluid density and SC transition temperature can be boosted with the increase in disorder strength,which should be general to quasicrystal but unusual to periodic systems,reflecting the interplay between the underlying geometry and disorder.展开更多
It has been established that Strong Cosmic Censorship Conjecture(SCCC)is respected by an asymptotically flat black hole with charge,but violated by a charged asymptotically de Sitter black hole.We studied the instabil...It has been established that Strong Cosmic Censorship Conjecture(SCCC)is respected by an asymptotically flat black hole with charge,but violated by a charged asymptotically de Sitter black hole.We studied the instability of the Cauchy horizon for an accelerating black hole in Einstein theory conformally coupled with a scalar field.The black hole is uncharged while having inner,outer,and acceleration horizons.In the limit of vanishing acceleration,denoted by A→0,it becomes asymptotically flat and extremal,with its acceleration horizon vanishing as well.By exploring the perturbation of the massless scalar field upon the accelerating black hole,whose decay rate is governed by the quasinormal mode spectra,we show that the SCCC is violated in the near-extremal regime and also in the A→0+limit.Our result is the first observation of a black hole violating the SCCC in an almost asymptotically Minkowskian flat regime,as well as the first example of a black hole violating the SCCC with neither charge nor rotation.展开更多
We observe a superfluid λ transition in the P-V criticality of charged Ad S black holes,within a holographic extended thermodynamics that considers the variation of Newton’s constant G.We calculate the critical expo...We observe a superfluid λ transition in the P-V criticality of charged Ad S black holes,within a holographic extended thermodynamics that considers the variation of Newton’s constant G.We calculate the critical exponents and find that they coincide with those of a superfluid transition in liquid4He and the Bose-Einstein condensation of hard-sphere Bose gas.Moreover,the independence of entropy and thermodynamic volume in the holographic framework allows us to construct a well-defined Ruppeiner metric.The associated scalar curvature suggests that the black holes show similar microscopic interactions with the hard-sphere Bose gas,where the superfluid(condensed)phase is dominated by repulsive interactions,while the normal(gas)phase is dominated by attractive interactions.These findings might provide us with new insights into the quantum aspect of charged Ad S black holes.展开更多
Chalcopyrite solar cells will have to play an important role to mitigate the climate crisis,because of their particularly low carbon emissions.Doping in these semiconductors is due to native defects and intentional al...Chalcopyrite solar cells will have to play an important role to mitigate the climate crisis,because of their particularly low carbon emissions.Doping in these semiconductors is due to native defects and intentional alkali impurities.The recent progress in efficiency has been made possible by post-deposition treatments with heavy alkalis.Tail states and band gap distribution are the main limitations for the open circuit voltage in state-of-the-art chalcopyrite solar cells.Further efficiency limitations are due to the increased diode factor because of metastable defect transitions.Alloying with Ag opens new possibilities of band-edge engineering,as well as seems to improve the diode factor.In state-of-the-art cells the back contact is passivated by a Ga gradient;considerable research has been done to passivate the back contact by structured or continuous dielectric layers.A leap forward in efficiency can be expected from tandem cells.Chalcopyrite solar cells show promising potential as bottom cells as well as top cells.展开更多
The search for new materials with Dirac points has been a fascinating subject of condensed matter physics.Here we first report the growth and band structure of HfGe_(0.92)Te single crystals featuring three different t...The search for new materials with Dirac points has been a fascinating subject of condensed matter physics.Here we first report the growth and band structure of HfGe_(0.92)Te single crystals featuring three different types of Dirac points.HfGe_(0.92)Te crystallizes in a nonsymmorphic tetragonal space group P4/nmm(No.129),having a square Ge-atom plane with vacancies of about 8%.Using angle-resolved photoemission spectroscopy(ARPES),the Dirac nodal line composed of conventional Dirac points vulnerable to spin-orbit coupling(SOC)is observed,accompanied by robust Dirac points protected by the nonsymmorphic symmetry against SOC and vacancies.In particular,spin-orbit Dirac points(SDPs)originating from the surface formed under significant SOC could exist based on ARPES and calculations.Quasi-two-dimensional(quasi-2D)characteristics are confirmed by angular-resolved magnetoresistance.HfGe_(0.92)Te bulk crystals can be easily exfoliated to flakes with a thickness of approximately 5 nm for the quasi-2D nature.Thus,HfGe_(0.92)Te provides a good platform to explore exotic topological phases or topological properties with three different types of Dirac points,which is a potential candidate to achieve novel 2D SDPs.展开更多
Using the extensively studied V_(2)O_(3) as a prototype system, we investigate the role of percolation in metal-insulator transition(MIT). We apply scanning microwave impedance microscopy to directly determine the met...Using the extensively studied V_(2)O_(3) as a prototype system, we investigate the role of percolation in metal-insulator transition(MIT). We apply scanning microwave impedance microscopy to directly determine the metallic phase fraction p and relate it to the macroscopic conductance G, which shows a sudden jump when p reaches the percolation threshold. Interestingly, the conductance G exhibits a hysteretic behavior against p, suggesting two different percolating processes upon cooling and warming. Based on our image analysis and model simulation, we ascribe such hysteretic behavior to different domain nucleation and growth processes between cooling and warming, which is likely caused by the decoupled structural and electronic transitions in V_(2)O_(3) during MIT. Our work provides a microscopic view of how the interplay of structural and electronic degrees of freedom affects MIT in strongly correlated systems.展开更多
We describe an optomechanical ratchet scheme to realize nonreciprocal transmission of a light field, which is based on the bias of the optical cavity’s frequency spectrum caused by mechanical ratchet interactions. Th...We describe an optomechanical ratchet scheme to realize nonreciprocal transmission of a light field, which is based on the bias of the optical cavity’s frequency spectrum caused by mechanical ratchet interactions. This approach to break the time-reversal symmetry of light propagation is universally valid in various optomechanical systems with ratchet-oscillator structures. We discuss specifically the implementation of an on-chip Casimir-ratchet optomechanical protocol and demonstrate the optical nonreciprocity with an extremely high isolation ratio and flexible controllability, which does not require external additional optical engineering. Our study opens a door for manipulating flexibly light propagation by using mechanical ratchet resonators, and has potential applications in the on-chip integration of nonreciprocal devices and harness of lateral Casimir forces.展开更多
The Square Kilometre Array(SKA)project consists of delivering two largest radio telescope arrays being built by the SKA Observatory(SKAO),which is an intergovernmental organization bringing together nations from aroun...The Square Kilometre Array(SKA)project consists of delivering two largest radio telescope arrays being built by the SKA Observatory(SKAO),which is an intergovernmental organization bringing together nations from around the world with China being one of the major member countries.The computing resources needed to process,distribute,curate and use the vast amount of data that will be generated by the SKA telescopes are too large for the SKAO to manage on its own.To address this challenge,the SKAO is working with the international community to create a shared,distributed data,computing and networking capability called the SKA Regional Centre Alliance.In this model,the SKAO will be supported by a global network of SKA Regional Centres(SRCs)distributed around the world in its member countries to build an end-to-end science data system that will provide astronomers with high-quality science products.SRCs undertake deep processing,scientific analysis,and long-term storage of the SKA data,as well as user support.China has been actively participating in and promoting the construction of SRCs.This paper introduces the international cooperation and ongoing prototyping of the global SRC network,the basis for the construction of the China SRC and describes in detail the progress of the China SRC prototype.The paper also presents examples of scientific applications of SKA precursor and pathfinder telescopes performed using resources from the China SRC prototype.Finally,the future prospects of the China SRC are presented.展开更多
To understand sound propagation and beam formation, the physical properties of soft tissues from the biosonar system of odontocetes should be explored. Based on the acoustic impedance distributions of biosonar systems...To understand sound propagation and beam formation, the physical properties of soft tissues from the biosonar system of odontocetes should be explored. Based on the acoustic impedance distributions of biosonar systems, these processes have been examined via numerical simulations. In this study, the images of a short-beaked common dolphin(Delphinus delphis) were obtained via computed tomography. Then, the dolphin was dissected to extract tissue samples for additional examination. In addition to the speed of sound and density measurements, the acoustic attenuation coefficients of the biosonar system in the forehead were tested. The results revealed that the inner layer of the forehead was characterized using low sound speed, low density, and high attenuation. Acoustic fields and beam patterns were then evaluated by setting acoustic attenuation coefficients at different levels. Sounds propagating along the low-attenuation path had a lesser reduction in amplitude. Beam directivities in near and far fields suggested that changes in attenuation distribution would cause beam patterns to shift. These results indicated the complexity of a dolphin’s sonar emission system and helped improve our understanding of sound energy attenuation via studies on the forehead of odontocetes.展开更多
This paper presents the results of a study that compares CTOM, a microscopic optical model potential(OMP), which is an optical model co-created by the China Nuclear Data Center & Tuebingen University, to CH89, whi...This paper presents the results of a study that compares CTOM, a microscopic optical model potential(OMP), which is an optical model co-created by the China Nuclear Data Center & Tuebingen University, to CH89, which is a typical phenomenological OMP.The respective OMPs were tested by applying them to the modelling of nucleon elastic scattering and(d,p) transfer reactions involving14C,36S, and58Ni targets at both low and relatively high energies. The results demonstrated that although both potentials successfully accounted for the angular distributions of both the elastic scattering and transfer cross sections, the absolute values of the transfer cross sections calculated using CTOM were approximately 25% larger than those calculated using CH89. This increased transfer cross sections allowed CTOM to produce single particle strength reduction factors for the three reactions that were consistent with those extracted from(e,e′p) reactions as well as with more recent(p,2p) and(p,pn) reactions. Notch tests suggested that nucleon elastic scattering and transfer reactions are sensitive to different regions of the OMP;accordingly,phenomenological OMPs, which are constrained only by elastic scattering cross sections, may not be sufficient for nucleon transfer reactions. Therefore, we suggest that microscopic OMPs, which reflect more theoretical considerations, should be preferred over phenomenological ones in calculations of direct nuclear reactions.展开更多
Antiferromagnets(AFMs)with chiral noncollinear spin structure have attracted great attention in recent years.However,the existing research has mainly focused on hexagonal chiral AFMs,such as Mn3Sn,Mn3Ga,Mn3Ge with low...Antiferromagnets(AFMs)with chiral noncollinear spin structure have attracted great attention in recent years.However,the existing research has mainly focused on hexagonal chiral AFMs,such as Mn3Sn,Mn3Ga,Mn3Ge with low crystalline symmetry.Here,we present our systematical study for the face-centered cubic noncollinear antiferromagnetic Mn3Pt.By varying the alloy composition(x),we have successfully fabricated antiferromagnetic Mn1-xPtx epitaxial films on MgO substrates and have observed a crystalline structure transition from L10 MnPt to L12 Mn3Pt.The Mn3Pt exhibits a large anomalous Hall effect,which is in the same order of magnitude as those of ferromagnetic materials.Moreover,a large thickness-evolved strain effect is revealed in Mn3Pt films by X-ray diffraction(XRD)analysis based on the Scherrer method.Our work explores Mn3Pt as a promising candidate for topological antiferromagnetic spintronics.展开更多
Nonradiative carrier recombinations at deep centers in semiconductors are of great importance for both fundamental physics and device engineering.In this article,we provide a revised analysis of Huang's original n...Nonradiative carrier recombinations at deep centers in semiconductors are of great importance for both fundamental physics and device engineering.In this article,we provide a revised analysis of Huang's original nonradiative multi-phonon(NMP)theory with ab initio calculations.First,we confirmed at the first-principles level that Huang's concise formula gives the same results as the matrix-based formula,and that Huang's high-temperature formula provides an analytical expression for the coupling constant in Marcus theory.Secondly,we correct for anharmonic effects by taking into account local phonon-mode variations for different charge states of a defect.The corrected capture rates for defects in GaN and SiC agree well with experiments.展开更多
Dynamo theory describes the magnetic field induced by the rotating,convecting and electrically conducting fluid in a celestial body.The classical ABC-flow model represents fast dynamo action,required to sustain such a...Dynamo theory describes the magnetic field induced by the rotating,convecting and electrically conducting fluid in a celestial body.The classical ABC-flow model represents fast dynamo action,required to sustain such a magnetic field.In this letter,Lagrangian coherent structures(LCSs)in the ABC-flow are detected through Finite-time Lyapunov exponents(FTLE).The flow skeleton is identified by extracting intersections between repelling and attracting LCSs.For the case A=B=C=1,the skeleton structures are made up from lines connecting two different types of stagnation points in the ABC-flow.The corresponding kinematic ABC-dynamo problem is solved using a spectral method,and the distribution of cigar-like magnetic structures visualized.Inherent links are found to exist between LCSs in the ABC-flow and induced magnetic structures,which provides insight into the mechanism behind the ABC-dynamo.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1404602)the National Natural Science Foundation of China(Grant Nos.92250302,12034010,12134007+2 种基金12074199)the Tianjin Municipal Natural Science Foundation(Grant Nos.21JCZDJC00150,and 22JCYBJC01150)the Higher Education Discipline Innovation Project(Grant No.B23045)。
文摘Erbium-doped lithium niobate(LN)on insulator active devices,such as lasers and amplifiers,have received increasing attention.The nonlinear optical oscillation in them at high power destabilizes the output of signals and cannot be ignored.In this study,we reported the experimental observation and theoretical analysis of the nonlinear optical oscillation in erbiumdoped lithium niobate-on-insulator(LNOI)microring resonators while scanning the pump wavelength.Under the same pump power,the number of oscillation cycles decreases when the wavelength scanning rate increases from 10.6 to 33.9 nm/μs.A theoretical model based on the competition between the thermo-optic nonlinearity and the photorefractive effect was introduced to interpret the oscillation in transmission.A series of parameters were obtained from the comparison between the theoretical and experimental results;some of them,the relaxation rates of the thermal and the electric field,are significantly different from those of undoped LNOI microcavities.This work provides a valuable reference for future applications of active LNOI devices.
基金supported by the Taishan Scholars Program of Shandong Province(Grant No.tsqn201909010)the Key Basic and Applied Research Program of Guangdong Province(Grant No.2019B030302010)+1 种基金the National Natural Science Foundation of China(Grant Nos.51901139,51971120,and U1902221)the Key R&D Program of Shandong Province(Grant No.2022CXGC020308)。
文摘Viscosity is a crucial dynamic property for alloy liquids.For alloy liquids with glass-forming ability,their viscosity undergoes a change of more than ten orders of magnitude upon cooling,and eventually,a transition from liquid to glassy state occurs when viscosity reaches 1012 Pa s.Nevertheless,the viscosity measurement in the supercooled liquid region(SLR)has been an experimental challenge.Here,in this work,by combining conventional and fast scanning calorimeters,the accurate viscosity of supercooled liquids for Au_(49)Ag_(5.5)Pd_(2.3)Cu_(26.9)Si_(16.3) and Zr_(44)Ti_(11)Cu_(10)Ni_(10)Be_(25) metallic glasses(MGs)was measured over a wide viscosity range of 10^(6)-10^(12) Pa s.Moreover,the viscosity range of 10^(6)-10^(8) Pa s is generally selected for thermoplastic forming(TPF),which takes advantage of the dramatic softening that MGs exhibit after being heated into the SLR.We further gave the TPF process window covering the range of processing temperature and time by utilizing the obtained viscosity data and timetemperature-transformation curves.The optimal time window avoiding property degradation was also determined,based on that there was no marked effect on the mechanical properties of MGs when crystallinity was below~5%.Our findings not only provide the accurate viscosity data in the SLR,but also determine the optimal process parameters for the TPF process.
基金supported by the National Natural Science Foundation of China(Grant Nos.11975235,12005077,12035016,and 12075202)Guangdong Basic and Applied Basic Research Foundation(Grant No.2021A1515012374)。
文摘We investigated the critical dynamical scalarization and descalarization of black holes within the framework of the EinsteinMaxwell-scalar theory featuring higher-order coupling functions.Both the critical scalarization and descalarization displayed first-order phase transitions.When examining the nonlinear dynamics near the threshold,we always observed critical solutions that are linearly unstable static scalarized black holes.The critical dynamical scalarization and descalarization share certain similarities with the typeⅠcritical gravitational collapse.However,their initial configurations,critical solutions,and final outcomes differ significantly.To provide further insights into the dynamical results,we conducted a comparative analysis involving static solutions and perturbative analysis.
文摘Strong interaction is believed to be described by a theory called Quantum Chromodynamics(QCD),an important sector of the Standard Model(SM)of particle physics.QCD is a strange and charming theory,just like the two names of its building blocks suggest and remains to be the least wellunderstood part of the SM.
基金supported by the National Natural Science Foundation of China(Grant Nos.12122504,12375046,and 12035005)the Innovative Research Group of Hunan Province(Grant No.2024JJ1006)+1 种基金the Natural Science Foundation of Hunan Province(Grant No.2023JJ30384)Hunan Provincial Major Sci-Tech Program(Grant No.2023ZJ1010)。
文摘In this study,we investigate the quasinormal modes(QNMs)of a Lorentz-violating spacetime,factoring in a cosmological constant,within the framework of Einstein-bumblebee gravity.Our findings reveal that the interaction of spacetime with an anisotropic bumblebee field imparts distinct contributions to the axial and polar sectors of the vector perturbations.This subsequently breaks the isospectrality typically observed in vector modes.Numerical evidence strongly indicates isospectral breaking in the vector modes of Einstein-bumblebee black holes:a pronounced breakage in the real part of the frequencies,while the imaginary component seems less affected.This isospectral breaking indicates the existence of two different waveforms in the Ringdown phase of the black hole,which provides a potential signal of quantum gravity observable in current experiments.
文摘Non-Hermitian systems featuring exceptional points(EPs)or spectral coalescences of eigenvalues and eigenfunctions have led to many surprisingly important applications, such as single-mode lasing, loss-induced transparency, and highprecision metrology. However, most previous demonstrations of EPs have necessitated at least two coupled modes,thereby limiting the achievement and utilization of EPs in a wide range of single-mode systems.
基金supported by the National Natural Science Foundation of China(Grant Nos.12274080,11874114,and 11875108)the National Youth Science Foundation of China(Grant No.12204105)+1 种基金the Educational Research Project for Young and Middle-aged Teachers of Fujian Province(Grant No.JAT210041)the Natural Science Foundation of Fujian Province(Grant Nos.2021J01574,and 2022J05116).
文摘Quantum systems that undergo quantum phase transitions exhibit divergent susceptibility and can be exploited as probes to estimate physical parameters.We generalize the dynamic framework for criticality-enhanced quantum sensing by the quantum Rabi model(QRM)to its anisotropic counterpart and derive the correspondingly analytical expressions for the quantum Fisher information(QFI).We find that the contributions of the rotating-wave and counterrotating-wave interaction terms are symmetric at the limit of the infinite ratio of qubit frequency to field frequency,with the QFI reaching a maximum for the isotropic QRM.At finite frequency scaling,we analytically derive the inverted variance of higher-order correction and find that it is more affected by the rotating-wave coupling than by the counterrotating-wave coupling.
基金supported by the National Natural Science Foundation of China(Grant Nos.12074031,12234016,12174024,11704029,and 11674025)。
文摘Using the attractive Hubbard model as an example,we theoretically investigate the gap function,superfluid density,and superconductivity(SC)transition temperature on the semiperiodic Penrose lattice.First,we clarify that the gap function,density of states,and superfluid density positively correlate to the extended degree of single-particle states around the Fermi energy.Second,we confirm that the paramagnetic component of the superfluid density does not decay to zero in the thermodynamic limit,which is completely diferent from periodic systems.Regardless of the scaling,the diference between diamagnetic and paramagnetic currents remains stable,consistent with recent experimental results showing that although the superfluid density is lower than that of a periodic system,the system has bulk SC.Third,we find that the superfluid density and SC transition temperature can be boosted with the increase in disorder strength,which should be general to quasicrystal but unusual to periodic systems,reflecting the interplay between the underlying geometry and disorder.
基金supported by the National Natural Science Foundation of China(Grant No.12005080)supported by the National Natural Science Foundation of China(Grant No.12205014)+1 种基金the Guangdong Basic and Applied Research Foundation(Grant No.217200003)the Talents Introduction Foundation of Beijing Normal University(Grant No.310432102)。
文摘It has been established that Strong Cosmic Censorship Conjecture(SCCC)is respected by an asymptotically flat black hole with charge,but violated by a charged asymptotically de Sitter black hole.We studied the instability of the Cauchy horizon for an accelerating black hole in Einstein theory conformally coupled with a scalar field.The black hole is uncharged while having inner,outer,and acceleration horizons.In the limit of vanishing acceleration,denoted by A→0,it becomes asymptotically flat and extremal,with its acceleration horizon vanishing as well.By exploring the perturbation of the massless scalar field upon the accelerating black hole,whose decay rate is governed by the quasinormal mode spectra,we show that the SCCC is violated in the near-extremal regime and also in the A→0+limit.Our result is the first observation of a black hole violating the SCCC in an almost asymptotically Minkowskian flat regime,as well as the first example of a black hole violating the SCCC with neither charge nor rotation.
基金supported by the National Natural Science Foundation of China(Grant Nos.12275183,12275184,12105191,and 12175212)。
文摘We observe a superfluid λ transition in the P-V criticality of charged Ad S black holes,within a holographic extended thermodynamics that considers the variation of Newton’s constant G.We calculate the critical exponents and find that they coincide with those of a superfluid transition in liquid4He and the Bose-Einstein condensation of hard-sphere Bose gas.Moreover,the independence of entropy and thermodynamic volume in the holographic framework allows us to construct a well-defined Ruppeiner metric.The associated scalar curvature suggests that the black holes show similar microscopic interactions with the hard-sphere Bose gas,where the superfluid(condensed)phase is dominated by repulsive interactions,while the normal(gas)phase is dominated by attractive interactions.These findings might provide us with new insights into the quantum aspect of charged Ad S black holes.
文摘Chalcopyrite solar cells will have to play an important role to mitigate the climate crisis,because of their particularly low carbon emissions.Doping in these semiconductors is due to native defects and intentional alkali impurities.The recent progress in efficiency has been made possible by post-deposition treatments with heavy alkalis.Tail states and band gap distribution are the main limitations for the open circuit voltage in state-of-the-art chalcopyrite solar cells.Further efficiency limitations are due to the increased diode factor because of metastable defect transitions.Alloying with Ag opens new possibilities of band-edge engineering,as well as seems to improve the diode factor.In state-of-the-art cells the back contact is passivated by a Ga gradient;considerable research has been done to passivate the back contact by structured or continuous dielectric layers.A leap forward in efficiency can be expected from tandem cells.Chalcopyrite solar cells show promising potential as bottom cells as well as top cells.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.51832010,51902055,11925408,12005251,and 11921004)National Key Research and Development Program of China(Grant Nos.2018YFE0202602,2018YFA0305700,and 2017YFA0302902)。
文摘The search for new materials with Dirac points has been a fascinating subject of condensed matter physics.Here we first report the growth and band structure of HfGe_(0.92)Te single crystals featuring three different types of Dirac points.HfGe_(0.92)Te crystallizes in a nonsymmorphic tetragonal space group P4/nmm(No.129),having a square Ge-atom plane with vacancies of about 8%.Using angle-resolved photoemission spectroscopy(ARPES),the Dirac nodal line composed of conventional Dirac points vulnerable to spin-orbit coupling(SOC)is observed,accompanied by robust Dirac points protected by the nonsymmorphic symmetry against SOC and vacancies.In particular,spin-orbit Dirac points(SDPs)originating from the surface formed under significant SOC could exist based on ARPES and calculations.Quasi-two-dimensional(quasi-2D)characteristics are confirmed by angular-resolved magnetoresistance.HfGe_(0.92)Te bulk crystals can be easily exfoliated to flakes with a thickness of approximately 5 nm for the quasi-2D nature.Thus,HfGe_(0.92)Te provides a good platform to explore exotic topological phases or topological properties with three different types of Dirac points,which is a potential candidate to achieve novel 2D SDPs.
基金Fudan University was supported by the National Natural Science Foundation of China (Grant Nos. 12074080, 11804052, 11827805,11725521, and 12035004)the National Postdoctoral Program for Innovative Talents (Grant No. BX20180079)+5 种基金the Shanghai Science and Technology Committee Rising-Star Program (Grant No. 19QA1401000)the Science and Technology Commission of Shanghai Municipality (Grant No.20JC1414700)the Major Project (Grant No. 2019SHZDZX01)the Ministry of Science and Technology of China (Grant Nos. 2017YFA03030002021YFA1400100)(synthesis, structural characterization and global transport of V2O3) at University of California San Diego was supported by the US Air Force Office of Scientific Research (Grant No.FA9550-20-1-0242)。
文摘Using the extensively studied V_(2)O_(3) as a prototype system, we investigate the role of percolation in metal-insulator transition(MIT). We apply scanning microwave impedance microscopy to directly determine the metallic phase fraction p and relate it to the macroscopic conductance G, which shows a sudden jump when p reaches the percolation threshold. Interestingly, the conductance G exhibits a hysteretic behavior against p, suggesting two different percolating processes upon cooling and warming. Based on our image analysis and model simulation, we ascribe such hysteretic behavior to different domain nucleation and growth processes between cooling and warming, which is likely caused by the decoupled structural and electronic transitions in V_(2)O_(3) during MIT. Our work provides a microscopic view of how the interplay of structural and electronic degrees of freedom affects MIT in strongly correlated systems.
基金supported by the National Natural Science Foundation of China(Grant No.12065008)the Key Project of Youth Science Foundation of Jiangxi Province(Grant No.20192ACBL21001)+2 种基金the Outstanding Youth Project of Jiangxi Province(Grant No.20192BCBL23007)supported by the National Natural Science Foundation of China(Grant No.11775190)supported by the National Natural Science Foundation of China(Grant No.11775035)。
文摘We describe an optomechanical ratchet scheme to realize nonreciprocal transmission of a light field, which is based on the bias of the optical cavity’s frequency spectrum caused by mechanical ratchet interactions. This approach to break the time-reversal symmetry of light propagation is universally valid in various optomechanical systems with ratchet-oscillator structures. We discuss specifically the implementation of an on-chip Casimir-ratchet optomechanical protocol and demonstrate the optical nonreciprocity with an extremely high isolation ratio and flexible controllability, which does not require external additional optical engineering. Our study opens a door for manipulating flexibly light propagation by using mechanical ratchet resonators, and has potential applications in the on-chip integration of nonreciprocal devices and harness of lateral Casimir forces.
基金supported by the National Key R&D Program of China(Grant No.2018YFA0404603)Chinese Academy of Sciences International Partner Program(Grant No.114231KYSB20170003)+2 种基金National Natural Science Foundation of China(Grant No.12041301)Youth Innovation Promotion AssociationChinese Academy of Sciences(Grant Nos.201664,and2021258)。
文摘The Square Kilometre Array(SKA)project consists of delivering two largest radio telescope arrays being built by the SKA Observatory(SKAO),which is an intergovernmental organization bringing together nations from around the world with China being one of the major member countries.The computing resources needed to process,distribute,curate and use the vast amount of data that will be generated by the SKA telescopes are too large for the SKAO to manage on its own.To address this challenge,the SKAO is working with the international community to create a shared,distributed data,computing and networking capability called the SKA Regional Centre Alliance.In this model,the SKAO will be supported by a global network of SKA Regional Centres(SRCs)distributed around the world in its member countries to build an end-to-end science data system that will provide astronomers with high-quality science products.SRCs undertake deep processing,scientific analysis,and long-term storage of the SKA data,as well as user support.China has been actively participating in and promoting the construction of SRCs.This paper introduces the international cooperation and ongoing prototyping of the global SRC network,the basis for the construction of the China SRC and describes in detail the progress of the China SRC prototype.The paper also presents examples of scientific applications of SKA precursor and pathfinder telescopes performed using resources from the China SRC prototype.Finally,the future prospects of the China SRC are presented.
基金supported by the National Key Research and Development Program of China (Grant Nos. 2018YFC1407504, and 2018YFC1407505)National Natural Science Foundation of China (Grant No. 12074323)+3 种基金Special Fund for Marine and Fishery Development of Xiamen (Grant No.20CZB015HJ01)Water Conservancy Science and Technology Innovation Project of Guangdong (Grant No. 2020-16)China Postdoctoral Science Foundation (Grant No. 2020M682086)China National Postdoctoral Program for Innovative Talents (Grant No. BX2021168)。
文摘To understand sound propagation and beam formation, the physical properties of soft tissues from the biosonar system of odontocetes should be explored. Based on the acoustic impedance distributions of biosonar systems, these processes have been examined via numerical simulations. In this study, the images of a short-beaked common dolphin(Delphinus delphis) were obtained via computed tomography. Then, the dolphin was dissected to extract tissue samples for additional examination. In addition to the speed of sound and density measurements, the acoustic attenuation coefficients of the biosonar system in the forehead were tested. The results revealed that the inner layer of the forehead was characterized using low sound speed, low density, and high attenuation. Acoustic fields and beam patterns were then evaluated by setting acoustic attenuation coefficients at different levels. Sounds propagating along the low-attenuation path had a lesser reduction in amplitude. Beam directivities in near and far fields suggested that changes in attenuation distribution would cause beam patterns to shift. These results indicated the complexity of a dolphin’s sonar emission system and helped improve our understanding of sound energy attenuation via studies on the forehead of odontocetes.
基金supported by the National Natural Science Foundation of China(Grant Nos.11775013,U1432247,11775316,U1630143,and 11465005)the National Key Research and Development Program(Grant No.2016YFA0400502)Science Challenge Project(Grant No.TZ2018001)
文摘This paper presents the results of a study that compares CTOM, a microscopic optical model potential(OMP), which is an optical model co-created by the China Nuclear Data Center & Tuebingen University, to CH89, which is a typical phenomenological OMP.The respective OMPs were tested by applying them to the modelling of nucleon elastic scattering and(d,p) transfer reactions involving14C,36S, and58Ni targets at both low and relatively high energies. The results demonstrated that although both potentials successfully accounted for the angular distributions of both the elastic scattering and transfer cross sections, the absolute values of the transfer cross sections calculated using CTOM were approximately 25% larger than those calculated using CH89. This increased transfer cross sections allowed CTOM to produce single particle strength reduction factors for the three reactions that were consistent with those extracted from(e,e′p) reactions as well as with more recent(p,2p) and(p,pn) reactions. Notch tests suggested that nucleon elastic scattering and transfer reactions are sensitive to different regions of the OMP;accordingly,phenomenological OMPs, which are constrained only by elastic scattering cross sections, may not be sufficient for nucleon transfer reactions. Therefore, we suggest that microscopic OMPs, which reflect more theoretical considerations, should be preferred over phenomenological ones in calculations of direct nuclear reactions.
基金the National Key R&D Program of China(Grant Nos.2017YFA0303202,and 2017YFA0305300)the National Natural Science Foundation of China(Grant Nos.11974260,11674246,51501131,51671147,11874283,51801152,and 11774064)+1 种基金the Natural Science Foundation of Shanghai(Grant Nos.17ZR1443700,and19ZR1478700)the Fundamental Research Funds for the Central Universities。
文摘Antiferromagnets(AFMs)with chiral noncollinear spin structure have attracted great attention in recent years.However,the existing research has mainly focused on hexagonal chiral AFMs,such as Mn3Sn,Mn3Ga,Mn3Ge with low crystalline symmetry.Here,we present our systematical study for the face-centered cubic noncollinear antiferromagnetic Mn3Pt.By varying the alloy composition(x),we have successfully fabricated antiferromagnetic Mn1-xPtx epitaxial films on MgO substrates and have observed a crystalline structure transition from L10 MnPt to L12 Mn3Pt.The Mn3Pt exhibits a large anomalous Hall effect,which is in the same order of magnitude as those of ferromagnetic materials.Moreover,a large thickness-evolved strain effect is revealed in Mn3Pt films by X-ray diffraction(XRD)analysis based on the Scherrer method.Our work explores Mn3Pt as a promising candidate for topological antiferromagnetic spintronics.
基金supported by the National Natural Science Foundation of China (Grand Nos. 61927901, 11674241, 11574304, and 11774338)supported by the Director, Office of Science (SC), Basic Energy Science (BES)/Materials Science and Engineering Division (MSED) of the US Department of Energy (DOE) (Grant No. DE-AC02-05CH11231) through the Theory of Material project
文摘Nonradiative carrier recombinations at deep centers in semiconductors are of great importance for both fundamental physics and device engineering.In this article,we provide a revised analysis of Huang's original nonradiative multi-phonon(NMP)theory with ab initio calculations.First,we confirmed at the first-principles level that Huang's concise formula gives the same results as the matrix-based formula,and that Huang's high-temperature formula provides an analytical expression for the coupling constant in Marcus theory.Secondly,we correct for anharmonic effects by taking into account local phonon-mode variations for different charge states of a defect.The corrected capture rates for defects in GaN and SiC agree well with experiments.
基金supported by the National Natural Science Foundation of China(Grant No.51979162)。
文摘Dynamo theory describes the magnetic field induced by the rotating,convecting and electrically conducting fluid in a celestial body.The classical ABC-flow model represents fast dynamo action,required to sustain such a magnetic field.In this letter,Lagrangian coherent structures(LCSs)in the ABC-flow are detected through Finite-time Lyapunov exponents(FTLE).The flow skeleton is identified by extracting intersections between repelling and attracting LCSs.For the case A=B=C=1,the skeleton structures are made up from lines connecting two different types of stagnation points in the ABC-flow.The corresponding kinematic ABC-dynamo problem is solved using a spectral method,and the distribution of cigar-like magnetic structures visualized.Inherent links are found to exist between LCSs in the ABC-flow and induced magnetic structures,which provides insight into the mechanism behind the ABC-dynamo.
