Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical pr...Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).展开更多
We present a review of our recent research in econophysics, and focus on the comparative study of Chinese and western financial markets. By virtue of concepts and methods in statistical physics, we investigate the tim...We present a review of our recent research in econophysics, and focus on the comparative study of Chinese and western financial markets. By virtue of concepts and methods in statistical physics, we investigate the time correlations and spatial structure of financial markets based on empirical high-frequency data. We discover that the Chinese stock market shares common basic properties with the western stock markets, such as the fat-tail probability distribution of price returns, the long-range auto-correlation of volatifities, and the persistence probability of volatilities, while it exhibits very different higher-order time correlations of price returns and volatilities, spatial correlations of individual stock prices, and large-fluctuation dynamic behaviors. Furthermore, multi-agent-based models are developed to simulate the microscopic interaction and dynamic evolution of the stock markets.展开更多
The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from th...The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from these two types of sources.The relevant parameters describing the shape of both components and the potential correlation between these parameters can provide important clues on the geometric and physical properties of the disk and the corona in these sources.In this work,we present a positive correlation between the photon indexΓand the reflection strength R for the low-mass BHXRBs in the hard state by modeling NuSTAR data,which is qualitatively consistent with the previous studies.We compare our results with the predictions from different theoretical disk-corona models.We show that the RIT correlation found in this work seems to favor the moving corona model proposed by Beloborodov.Our results indicate that the coronal geometry varies significantly among BHXRBs.We further compare our results with that of AGNs.We find that the reflection strength R is smaller than unity in the hard state of BHXRBs,while it can be as large as~5 in AGNs,which implies that the variations of the disk-coronal geometry of AGNs are more vigorous than that of the BHXRBs in the hard state.展开更多
We focus on the effect of ionic radius of lanthanides and the number of electrons in 4f orbitals on the superconducting temperature in 12442-type iron-based superconductors RbLn_(2)Fe_(4)As_(4)O_(2)(Ln=Sm and Ho).Elec...We focus on the effect of ionic radius of lanthanides and the number of electrons in 4f orbitals on the superconducting temperature in 12442-type iron-based superconductors RbLn_(2)Fe_(4)As_(4)O_(2)(Ln=Sm and Ho).Electronic properties of RbSm_(2)Fe_(4)As_(4)O_(2) and RbHo2Fe4As4O2with the largest differences of ionic radii and numbers of electrons in 4f orbital,and the largest difference of superconducting temperatures by using firstprinciples calculations.We predict that the ground state of RbLn_(2)Fe_(4)As_(4)O_(2) is spin-density-wave-type in-plane striped antiferromagnet,and the magnetic moment around each Fe atom is about 2μB.RbSm_(2)Fe_(4)As_(4)O_(2)has a great influence on the energy band near theΓpoint,and a Dirac-like dispersion energy band appears.This band is mainly contributed by the dz2orbital of Fe,which proves that RbSm_(2)Fe_(4)As_(4)O_(2)has a stronger threedimensionality.At the same time,this extra Fermi surface appears at theΓpoint,which also shows that Sm can effectively enhance the coupling strength within Fe2As2bilayers.This is also confirmed by the charge density differenceρ(RbHo_(2)Fe_(4)As_(4)O_(2))-ρ(RbSm_(2)Fe_(4)As_(4)O_(2)).It increases the internal coupling strength of the bilayer Fe_(2)As2layers,which in turn leads to a higher Tcof RbSm_(2)Fe_(4)As_(4)O_(2)than RbHo_(2)Fe_(4)As_(4)O_(2).Determining the details of their electronic structure,which may be closely related to superconductivity,is crucial to understanding the underlying mechanism.Such microscopic studies provide useful clues for our further research of other hightemperature superconductors.展开更多
We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions.The conventional way to apply...We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions.The conventional way to apply the rotating wave approximation in a driven high-spin system is to assume the dynamics being restricted in the reduced Hilbert space.However,when the driving strength is relatively strong or the driving is off resonant,the leakage from the target resonance subspace cannot be neglected for a multi-level quantum system.We propose the correct formalism to apply the rotating wave approximation in the full Hilbert space by taking this leakage into account.By estimating the operator fidelity of the time propagator,our formalism applied in the full Hilbert space unambiguously manifests great advantages over the conventional method applied in the reduced Hilbert space.展开更多
Intercalated transition metal dichalcogenides(TMDCs)attract much attention due to their rich properties and potential applications.In this article,we grew successfully high-quality V_(1/3)TaS_(2) crystals by a vapor t...Intercalated transition metal dichalcogenides(TMDCs)attract much attention due to their rich properties and potential applications.In this article,we grew successfully high-quality V_(1/3)TaS_(2) crystals by a vapor transport method.We measured the magnetization,longitudinal resistivityρxx(T,H),Hall resistivityρxy(T,H),as well as performed calculations of the electronic band structure.It was found that V_(1/3)TaS_(2) is an A-type antiferromagnet with the Neel temperature T_(N)=6.20 K,and exhibits a negative magnetoresistance(MR)near T_(N).Both band structure calculations and Hall resistivity measurements demonstrated it is a magnetic semimetal.展开更多
Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS material...Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ(Ga,Mn)As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature TCo f 230 K has been achieved in(Ba,K)(Zn,Mn)2As2. However, most DMSs, including(Ga,Mn)As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba(Zn,Co)2As2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance(NMR) and muon spin rotation(μSR).展开更多
A preparative technique to obtain water soluble C_(60)-liposome by means of molecular package of C_(60) with lecithin has been established.The concentration of C_(60) presented in liposome is 1.09 x 10-4mol/dm3.The mo...A preparative technique to obtain water soluble C_(60)-liposome by means of molecular package of C_(60) with lecithin has been established.The concentration of C_(60) presented in liposome is 1.09 x 10-4mol/dm3.The molecular system of C_(60)-liposome with human cervix cancer cells is irradiated with laser(570nm,800mW),there is obvious biological effect of C_(60) to huma cervix cancer cells.展开更多
Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Rec...Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Recently, a series of bulk form DMSs isostructural to iron-based superconductors have been reported, which can be readily investigated by microscopic experimental techniques such as nuclear magnetic resonance (NMR) and muon spin rotation (μSR). The measurements have demonstrated that homogeneous ferromagnetism is achieved in these DMSs. In this review article, we summarize experimental evidences from both NMR and μSR measurements. NMR results have shown that carriers facilitate the interactions between distant Mn atoms, while μSR results indicate that these bulk form DMSs and (Ga,Mn)As share a common mechanism for the ferromagnetic exchange interactions.展开更多
A novel setup of saturated absorption spectroscopy (SAS) is presented.It is based on laser reflections at surfaces of a sample vapor cell.It only needs one cell and one photodiode and is more compact than conventional...A novel setup of saturated absorption spectroscopy (SAS) is presented.It is based on laser reflections at surfaces of a sample vapor cell.It only needs one cell and one photodiode and is more compact than conventional setups of SAS.Its spectrum is similar to a conventional SAS.The frequency stabilization performance of an external-cavity diode laser with this setup is investigated.A frequency stability of 1.1 × 10^(-11) is achieved at an averaging time of 60s in the Allen variance measurements.展开更多
Pb1-x Srx Te thin films with different strontium (St) compositions axe grown on BaF2 (111) substrates by molecular beam epitaxy (MBE). Using high resolution x-ray diffraction (HPLXRD), we obtain Pb1-xSrxTe lat...Pb1-x Srx Te thin films with different strontium (St) compositions axe grown on BaF2 (111) substrates by molecular beam epitaxy (MBE). Using high resolution x-ray diffraction (HPLXRD), we obtain Pb1-xSrxTe lattice constants, which vary in the range 6.462-6.492 A. According to the Vegard law and HRXRD data, Sr compositions in Pb1-xSrxTe thin films range from 0.0-8.0%. The Pb1-xSrxTe refractive index dispersions are attained from infrared transmission spectrum characterized by Fourier transform infrared (FTIR) transmission spectroscopy. It is found that refractive index decreases while Sr content increases in Pb1-xSrx Te. We also simulate the Pb1-xSrxTe transmission spectra theoretically to obtain the optical band gap energies which range between 0.320 e V and 0.449 e V. The simulated results are in good agreement with the FTIR data. Finally, we determine the relation between Pb1-xSrx Te band gap energies and Sr compositions (Eg = 0.320+0.510x-0.930x^2 +184x^3 (eV)).展开更多
The dynamic behaviours of the translocations of closed circular polymers and closed knotted polymers through a nanopore, under the driving of an applied field, are studied by three-dimensional Langevin dynamics sinmla...The dynamic behaviours of the translocations of closed circular polymers and closed knotted polymers through a nanopore, under the driving of an applied field, are studied by three-dimensional Langevin dynamics sinmlations. The power-law scaling of the translocation time T with the chain length N and the distribution of translocation time are investigated separately. For closed circular polymers, a crossover scaling of translocation time with chain length is found to be T - N^a with the exponent a varying from a = 0.71 for relatively short chains to a = 1.29 for longer chains under driving force F = 5. The scaling behaviour for longer chains is in good agreement with experimental results, in which the exponent α= 1.27 for the transloeation of double-strand DNA. The distribution of translocation time D(τ) is close to a Gaussian function for duration time τ 〈 τp and follows a falling exponential function for duration time T 〉 wp. For closed knotted polymers, the scaling exponent a is 1.27 for small field force (F = 5) and 1.38 for large field force (F = 10). The distribution of translocation time D(τ) remarkably features two peaks appearing in the case of large driving force. The interesting result of multiple peaks can conduce to the understanding of the influence of the number of strands of polymers in the pore at the same time on translocation dynamic process and scaling property.展开更多
The second class of high-temperature superconductors (HTSCs), iron-based pnictides and chalcogenides, necessarily contain Fe2X2 ("X" refers to a pnictogen or a chalcogen element) layers, just like the first clas...The second class of high-temperature superconductors (HTSCs), iron-based pnictides and chalcogenides, necessarily contain Fe2X2 ("X" refers to a pnictogen or a chalcogen element) layers, just like the first class of HTSCs which possess the essential CuO2 sheets. So far, dozens of iron-based HTSCs, classified into nine groups, have been discovered. In this article, the crystal-chemistry aspects of the known iron-based superconductors are reviewed and summarized by employing "hard and soft acids and bases (HSAB)" concept. Based on these understandings, we propose an alternative route to exploring new iron-based superconductors via rational structural design.展开更多
Single crystal PbTe thin films have been grown on BaF2 (111) by using solid source molecular beam epitaxy. The studies of evolution of the surface morphology with the increasing growth temperature from 375 to 525℃ ...Single crystal PbTe thin films have been grown on BaF2 (111) by using solid source molecular beam epitaxy. The studies of evolution of the surface morphology with the increasing growth temperature from 375 to 525℃ by AFM show that PbTe epilayers exhibit smooth surface morphologies with atomic layer scale roughness and are crack free. It is found that for PbTe grown at 475℃, the morphology is dominated by triangles and the rms roughness is 3.987nm. Compared to the rms roughnesses of 0.432nm and 0.759nm for the samples grown at 375 and 525℃ respectively, the surface of the PbTe layer grown at 475℃ is much rougher. This roughening transition is due to the interaction between the elastic relaxation and the plastic relaxation during the strain relaxation process. In contrast to the result of the morphology that the PbTe epitaxial layer grown at 375℃ has most smooth surface, as observed from the line width of x-ray diffraction curves at higher growth temperature improves the crystal quality of the single-crystalline Pb Te layer.展开更多
The vectorial structure of an optical field with hybrid states of polarization (SOP) in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal ...The vectorial structure of an optical field with hybrid states of polarization (SOP) in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial SoP of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.展开更多
The scattering of scalar light wave from a random medium with a correlation function of Gaussian-Schell model distribution is studied. It is shown that the properties of the scattered field, i.e., the spectral density...The scattering of scalar light wave from a random medium with a correlation function of Gaussian-Schell model distribution is studied. It is shown that the properties of the scattered field, i.e., the spectral density and the spectral degree of coherence of the scattered field, are closely related to the properties of the scattering medium, including the scaled effective radius and the scaled correlation length of the correlation function.展开更多
We study the motion of a spiral wave controlled by a local periodic forcing imposed on a region around the spiral tip in an excitable medium. Three types of trajectories of spiral tip are observed: the epicycloid-lik...We study the motion of a spiral wave controlled by a local periodic forcing imposed on a region around the spiral tip in an excitable medium. Three types of trajectories of spiral tip are observed: the epicycloid-like meandering, the resonant drift, and the hypocycloid-like meandering. The frequency of the spiral is sensitive to the local periodic forcing. The dependency of spiral frequency on the amplitude and size of local periodic forcing are presented. In addition, we show how the drift speed and direction are adjusted by the amplitude and phase of local periodic forcing, which is consistent with a theoretical analysis based on the weak deformation approximation.展开更多
The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, de...The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.展开更多
An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly(α-methylstyrene)(PαMS) chains is studied, in which the effect of large side group...An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly(α-methylstyrene)(PαMS) chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFE0202700 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.11974422 and 12104504)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)Fundamental Research Funds for the Central Universities,and Research Funds of Renmin University,China(Grant No.22XNKJ30)supported by the Outstanding Innovative Talents Cultivation Funded Programs 2023 of Renmin University,China。
文摘Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).
基金supported by the National Natural Science Foundation of China(Grant Nos.11375149,11075137,and J1210046)the Natural Science Foundationof Zhejiang Province of China(Grant No.Z6090130)
文摘We present a review of our recent research in econophysics, and focus on the comparative study of Chinese and western financial markets. By virtue of concepts and methods in statistical physics, we investigate the time correlations and spatial structure of financial markets based on empirical high-frequency data. We discover that the Chinese stock market shares common basic properties with the western stock markets, such as the fat-tail probability distribution of price returns, the long-range auto-correlation of volatifities, and the persistence probability of volatilities, while it exhibits very different higher-order time correlations of price returns and volatilities, spatial correlations of individual stock prices, and large-fluctuation dynamic behaviors. Furthermore, multi-agent-based models are developed to simulate the microscopic interaction and dynamic evolution of the stock markets.
基金funded by the National Aeronautics and Space Administrationsupported by the National Natural Science Foundation of China(11833007,12073023,12233007,and 12147103)+1 种基金the science research grants from the China Manned Space Project with No.CMS-CSST-2021-A06the fundamental research fund for Chinese central universities(Zhejiang University)。
文摘The power law and reflection emission have been observed in the X-ray spectra of both black hole X-ray binaries(BHXRBs)and active galactic nuclei(AGNs),indicating a common physical origin of the X-ray emission from these two types of sources.The relevant parameters describing the shape of both components and the potential correlation between these parameters can provide important clues on the geometric and physical properties of the disk and the corona in these sources.In this work,we present a positive correlation between the photon indexΓand the reflection strength R for the low-mass BHXRBs in the hard state by modeling NuSTAR data,which is qualitatively consistent with the previous studies.We compare our results with the predictions from different theoretical disk-corona models.We show that the RIT correlation found in this work seems to favor the moving corona model proposed by Beloborodov.Our results indicate that the coronal geometry varies significantly among BHXRBs.We further compare our results with that of AGNs.We find that the reflection strength R is smaller than unity in the hard state of BHXRBs,while it can be as large as~5 in AGNs,which implies that the variations of the disk-coronal geometry of AGNs are more vigorous than that of the BHXRBs in the hard state.
基金supported by the National Natural Science Foundation of China(Grant Nos.11904319 and 11974354)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ18A040002)。
文摘We focus on the effect of ionic radius of lanthanides and the number of electrons in 4f orbitals on the superconducting temperature in 12442-type iron-based superconductors RbLn_(2)Fe_(4)As_(4)O_(2)(Ln=Sm and Ho).Electronic properties of RbSm_(2)Fe_(4)As_(4)O_(2) and RbHo2Fe4As4O2with the largest differences of ionic radii and numbers of electrons in 4f orbital,and the largest difference of superconducting temperatures by using firstprinciples calculations.We predict that the ground state of RbLn_(2)Fe_(4)As_(4)O_(2) is spin-density-wave-type in-plane striped antiferromagnet,and the magnetic moment around each Fe atom is about 2μB.RbSm_(2)Fe_(4)As_(4)O_(2)has a great influence on the energy band near theΓpoint,and a Dirac-like dispersion energy band appears.This band is mainly contributed by the dz2orbital of Fe,which proves that RbSm_(2)Fe_(4)As_(4)O_(2)has a stronger threedimensionality.At the same time,this extra Fermi surface appears at theΓpoint,which also shows that Sm can effectively enhance the coupling strength within Fe2As2bilayers.This is also confirmed by the charge density differenceρ(RbHo_(2)Fe_(4)As_(4)O_(2))-ρ(RbSm_(2)Fe_(4)As_(4)O_(2)).It increases the internal coupling strength of the bilayer Fe_(2)As2layers,which in turn leads to a higher Tcof RbSm_(2)Fe_(4)As_(4)O_(2)than RbHo_(2)Fe_(4)As_(4)O_(2).Determining the details of their electronic structure,which may be closely related to superconductivity,is crucial to understanding the underlying mechanism.Such microscopic studies provide useful clues for our further research of other hightemperature superconductors.
基金the National Key Research and Development Program of China(Grant Nos.2017YFA0304202 and 2017YFA0205700)the National Natural Science Foundation of China(Grant Nos.11875231 and 11935012)the Fundamental Research Funds for the Central Universities(Grant No.2018FZA3005).
文摘We investigate the rotating wave approximation applied in the high-spin quantum system driven by a linearly polarized alternating magnetic field in the presence of quadrupole interactions.The conventional way to apply the rotating wave approximation in a driven high-spin system is to assume the dynamics being restricted in the reduced Hilbert space.However,when the driving strength is relatively strong or the driving is off resonant,the leakage from the target resonance subspace cannot be neglected for a multi-level quantum system.We propose the correct formalism to apply the rotating wave approximation in the full Hilbert space by taking this leakage into account.By estimating the operator fidelity of the time propagator,our formalism applied in the full Hilbert space unambiguously manifests great advantages over the conventional method applied in the reduced Hilbert space.
基金Project supported by the National Key Research and Development Program of China(Grant No.2022YFA1403202)the National Natural Science Foundation of China(Grant Nos.NSFC-12074335,11974095,5177115,11974095,and 12188101)the Natural Science Foundation of Shaanxi Province of China(Grant No.2022JM-028).
文摘Intercalated transition metal dichalcogenides(TMDCs)attract much attention due to their rich properties and potential applications.In this article,we grew successfully high-quality V_(1/3)TaS_(2) crystals by a vapor transport method.We measured the magnetization,longitudinal resistivityρxx(T,H),Hall resistivityρxy(T,H),as well as performed calculations of the electronic band structure.It was found that V_(1/3)TaS_(2) is an A-type antiferromagnet with the Neel temperature T_(N)=6.20 K,and exhibits a negative magnetoresistance(MR)near T_(N).Both band structure calculations and Hall resistivity measurements demonstrated it is a magnetic semimetal.
基金Project supported by the Chinese Ministry of Science and Technology(Grant No.2016YFA0300402)the National Natural Science Foundation of China(Grant No.11574265)+1 种基金the Natural Science Foundation of Zhejiang Province,China(Grant Nos.LR15A040001 and LY14A040007)the Fundamental Research Funds for the Central Universities,China
文摘Diluted ferromagnetic semiconductors(DMSs) that combine the properties of semiconductors with ferromagnetism have potential application in spin-sensitive electronic(spintronic) devices. The search for DMS materials exploded after the observation of ferromagnetic ordering in Ⅲ-Ⅴ(Ga,Mn)As films. Recently, a series of DMS compounds isostructural to iron-based superconductors have been reported. Among them, the highest Curie temperature TCo f 230 K has been achieved in(Ba,K)(Zn,Mn)2As2. However, most DMSs, including(Ga,Mn)As, are p-type, i.e., the carriers that mediate the ferromagnetism are holes. For practical applications, DMSs with n-type carriers are also advantageous. Very recently,a new DMS Ba(Zn,Co)2As2 with n-type carriers has been synthesized. Here we summarize the recent progress on this research stream. We will show that the homogeneous ferromagnetism in these bulk form DMSs has been confirmed by microscopic techniques, i.e., nuclear magnetic resonance(NMR) and muon spin rotation(μSR).
基金the National Natural Science Foundation of China,and Science Foundation of Zhejiang Province,P.R.China.
文摘A preparative technique to obtain water soluble C_(60)-liposome by means of molecular package of C_(60) with lecithin has been established.The concentration of C_(60) presented in liposome is 1.09 x 10-4mol/dm3.The molecular system of C_(60)-liposome with human cervix cancer cells is irradiated with laser(570nm,800mW),there is obvious biological effect of C_(60) to huma cervix cancer cells.
基金supported by MOST (No. 2016YFA0300402)NSF of China (No. 11574265)the Fundamental Research Funds for the Central Universities
文摘Diluted magnetic semiconductors (DMSs) that possess both properties of semiconductors and ferromagnetism, have attracted a lot of attentions due to its potential applications for spin-sensitive electronic devices. Recently, a series of bulk form DMSs isostructural to iron-based superconductors have been reported, which can be readily investigated by microscopic experimental techniques such as nuclear magnetic resonance (NMR) and muon spin rotation (μSR). The measurements have demonstrated that homogeneous ferromagnetism is achieved in these DMSs. In this review article, we summarize experimental evidences from both NMR and μSR measurements. NMR results have shown that carriers facilitate the interactions between distant Mn atoms, while μSR results indicate that these bulk form DMSs and (Ga,Mn)As share a common mechanism for the ferromagnetic exchange interactions.
基金The project supported in part by National Natural Science Foundation of China and the Natural Science Foundation of Zhejiang Province of China. We acknowledge useful discussions with X. Feng, T. Xiang, and Y. Yu.
基金Supported by the National Basic Research Program of China under Grant No 2012CB921602the National Natural Science Foundation of China under Grant Nos 10874012 and 10974177the Program of International Science and Technology Cooperation of China under Grant No 2010DFA04690.
文摘A novel setup of saturated absorption spectroscopy (SAS) is presented.It is based on laser reflections at surfaces of a sample vapor cell.It only needs one cell and one photodiode and is more compact than conventional setups of SAS.Its spectrum is similar to a conventional SAS.The frequency stabilization performance of an external-cavity diode laser with this setup is investigated.A frequency stability of 1.1 × 10^(-11) is achieved at an averaging time of 60s in the Allen variance measurements.
基金Supported by the Key Project of National Natural Science Foundation of China under Grant No 10434090.
文摘Pb1-x Srx Te thin films with different strontium (St) compositions axe grown on BaF2 (111) substrates by molecular beam epitaxy (MBE). Using high resolution x-ray diffraction (HPLXRD), we obtain Pb1-xSrxTe lattice constants, which vary in the range 6.462-6.492 A. According to the Vegard law and HRXRD data, Sr compositions in Pb1-xSrxTe thin films range from 0.0-8.0%. The Pb1-xSrxTe refractive index dispersions are attained from infrared transmission spectrum characterized by Fourier transform infrared (FTIR) transmission spectroscopy. It is found that refractive index decreases while Sr content increases in Pb1-xSrx Te. We also simulate the Pb1-xSrxTe transmission spectra theoretically to obtain the optical band gap energies which range between 0.320 e V and 0.449 e V. The simulated results are in good agreement with the FTIR data. Finally, we determine the relation between Pb1-xSrx Te band gap energies and Sr compositions (Eg = 0.320+0.510x-0.930x^2 +184x^3 (eV)).
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 20574052, 20774066, 20974081 and 20934004)the Program for New Century Excellent Talents in University,China (Grant No. NCET-05-0538)the Natural Science Foundation of Zhejiang Province, China (Grant No. Y4090098)
文摘The dynamic behaviours of the translocations of closed circular polymers and closed knotted polymers through a nanopore, under the driving of an applied field, are studied by three-dimensional Langevin dynamics sinmlations. The power-law scaling of the translocation time T with the chain length N and the distribution of translocation time are investigated separately. For closed circular polymers, a crossover scaling of translocation time with chain length is found to be T - N^a with the exponent a varying from a = 0.71 for relatively short chains to a = 1.29 for longer chains under driving force F = 5. The scaling behaviour for longer chains is in good agreement with experimental results, in which the exponent α= 1.27 for the transloeation of double-strand DNA. The distribution of translocation time D(τ) is close to a Gaussian function for duration time τ 〈 τp and follows a falling exponential function for duration time T 〉 wp. For closed knotted polymers, the scaling exponent a is 1.27 for small field force (F = 5) and 1.38 for large field force (F = 10). The distribution of translocation time D(τ) remarkably features two peaks appearing in the case of large driving force. The interesting result of multiple peaks can conduce to the understanding of the influence of the number of strands of polymers in the pore at the same time on translocation dynamic process and scaling property.
基金supported by the National Natural Science Foundation of China(Grant Nos.90922002 and 11190023)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(Grant No.2013FZA3003)
文摘The second class of high-temperature superconductors (HTSCs), iron-based pnictides and chalcogenides, necessarily contain Fe2X2 ("X" refers to a pnictogen or a chalcogen element) layers, just like the first class of HTSCs which possess the essential CuO2 sheets. So far, dozens of iron-based HTSCs, classified into nine groups, have been discovered. In this article, the crystal-chemistry aspects of the known iron-based superconductors are reviewed and summarized by employing "hard and soft acids and bases (HSAB)" concept. Based on these understandings, we propose an alternative route to exploring new iron-based superconductors via rational structural design.
基金Supported by the National Natural Science Foundation of China under Grant No 10434090.
文摘Single crystal PbTe thin films have been grown on BaF2 (111) by using solid source molecular beam epitaxy. The studies of evolution of the surface morphology with the increasing growth temperature from 375 to 525℃ by AFM show that PbTe epilayers exhibit smooth surface morphologies with atomic layer scale roughness and are crack free. It is found that for PbTe grown at 475℃, the morphology is dominated by triangles and the rms roughness is 3.987nm. Compared to the rms roughnesses of 0.432nm and 0.759nm for the samples grown at 375 and 525℃ respectively, the surface of the PbTe layer grown at 475℃ is much rougher. This roughening transition is due to the interaction between the elastic relaxation and the plastic relaxation during the strain relaxation process. In contrast to the result of the morphology that the PbTe epitaxial layer grown at 375℃ has most smooth surface, as observed from the line width of x-ray diffraction curves at higher growth temperature improves the crystal quality of the single-crystalline Pb Te layer.
基金supported by the Zhejiang Provincial Natural Science Foundation,China(Grant Nos.LZ17A040001 and LY16A040014)the National Natural Science Foundation of China(Grant Nos.11574271 and 11574272)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministrythe Science Research Foundation of Zhejiang Sci-Tech University(ZSTU),China(Grant No.14062078-Y)
文摘The vectorial structure of an optical field with hybrid states of polarization (SOP) in the near-field is studied by using the angular spectrum method of an electromagnetic beam. Physical images of the longitudinal components of evanescent waves are illustrated and compared with those of the transverse components from the vectorial structure. Our results indicate that the relative weight integrated over the transverse plane of the evanescent wave depends strongly on the number of the polarization topological charges. The shapes of the intensity profiles of the longitudinal components are different from those of the transverse components, and it can be manipulated by changing the initial SoP of the field cross-section. The longitudinal component of evanescent wave dominates the near-field region. In addition, it also leads to three-dimensional shape variations of the optical field and the optical spin angular momentum flux density distributions.
基金Project supported by the National Natural Science Foundation of China(Grant No.10874150)the Natural Science Foundation of Zhejiang Province of China(Grant No.R1090168)the Program for New Century Excellent Talents in University(Grant No.NCET-07-0760)
文摘The scattering of scalar light wave from a random medium with a correlation function of Gaussian-Schell model distribution is studied. It is shown that the properties of the scattered field, i.e., the spectral density and the spectral degree of coherence of the scattered field, are closely related to the properties of the scattering medium, including the scaled effective radius and the scaled correlation length of the correlation function.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274271)the Scientific Research Foundation of Education Bureau of Zhejiang Province,China(Grant No.Y201224250)
文摘We study the motion of a spiral wave controlled by a local periodic forcing imposed on a region around the spiral tip in an excitable medium. Three types of trajectories of spiral tip are observed: the epicycloid-like meandering, the resonant drift, and the hypocycloid-like meandering. The frequency of the spiral is sensitive to the local periodic forcing. The dependency of spiral frequency on the amplitude and size of local periodic forcing are presented. In addition, we show how the drift speed and direction are adjusted by the amplitude and phase of local periodic forcing, which is consistent with a theoretical analysis based on the weak deformation approximation.
基金Project supported by the National Basic Research Program (973) of China (No. 10574109)the Zhejiang Provincial Science and Technology Department (No. 2005C24008)the Natural Science Foundation of Zhejiang Province (No. Y604064), China
文摘The unperturbed dimension and temperature character of poly(dibenzyl itaconate)s (PDBzI) are studied by a revised rotational isomeric state (RIS) method. The improved formulas of the mean-square radius of gyration, deduced by the pseudo-stereochemical equilibrium approach, may be used to investigate the configurational-conformational properties of atactic polymers with large side groups [poly(itaconates) for instance]. The calculated results showed that poly(itaconates) have larger dimension of the molecule than other vinyl polymers. Comparison of the dimension between considering and without considering side groups showed that the effect of large side groups on the unperturbed dimension for short-chain polymers is more obvious than that of long-chain polymers and, if the dimension of side groups increases, the effect also increases. The dimension differences of PDBzI between short-chain and long-chain polymers are investigated by the relation of characteristic ratios and temperature coefficients with temperature. Moreover, the dependence between the temperature coefficients and the tacticity of chains shows that the temperature characters of the isotactic, syndiotactic and atactic PDBzI chains have remarkable difference.
文摘An improved configurational-confomational statistical method is developed and the mean-square radius of gyration for atactic poly(α-methylstyrene)(PαMS) chains is studied, in which the effect of large side groups is considered. The deduced formulas, based on the rotational isomer state theory, are used to investigate the configuration-dependent properties of the atactic polymer chain, and the statistical correlation of the unperturbed polymer chain dimension and structure parameters are calculated. For the fraction of meso dyads Wm= 0.4, the dependence of the radius of gyration Rg and the intrinsic viscosity [η] on the molecule mass M are Rg = 2.63×10^-2 M^0.50 nm and [η] = 7.36 × 10^-2 M^0.497, respectively, which are in agreement with the previous experimental data for the PαMS samples. A small hump is detected in the curve of the characteristic ratio of the unperturbed mean-square radius of gyration versus the chain length for short PαMS chains. The Rg increases linearly with the temperature T, and the effects of the chain length and the tacticity on the temperature coefficient are remarkable. These are quite different from the results for PαMS chains not considering side groups or for the monosubstituted polystyrene chain.