[WT]Phase structures, the transport and magnetic properties of the Perovskite-type manganite （La 0.8-xCexSr 0.2） 0.97 MnO3 （x=0～0.26） prepared by La2O3 containing CeO2 with different contents were studied. Experi...[WT]Phase structures, the transport and magnetic properties of the Perovskite-type manganite （La 0.8-xCexSr 0.2） 0.97 MnO3 （x=0～0.26） prepared by La2O3 containing CeO2 with different contents were studied. Experiments show that the compounds consist of a magnetic perovskite phase and non-magnetic CeO2 and Mn3O4. The resistivity and magnetoresistance ratio （MR） of the samples vary with changing x. Their room-temperature MR reaches -3%～-14% at the magnetic field of 1 T. For x=0; x=0.037 and x=0.26 samples, the conductance keeps unchanged basically in a relatively wide temperature range above 600 K, and the result shows that it is feasible for producing SOFC cathode materials with these samples.展开更多
The replica trick used in the renormalization group(RG)for the disordered spin systems is discussed.The recursion relations of RG are derived in a more general situation in which the coupling constants can have arbitr...The replica trick used in the renormalization group(RG)for the disordered spin systems is discussed.The recursion relations of RG are derived in a more general situation in which the coupling constants can have arbitrary symmetry to the replica indices.It is shown that the random fixed point found by Luther,Grinstein and Lubensky is unstable.This instability implies that the replica symmetry should be broken in the RG for the disordered systems.展开更多
This paper studies a new electron irradiation effect of the formation,movement and growth of stacking fault in YBa_(2) Cu_(3) O_(6+x).The energy of electron irradiation is about 160keV.It would be a promising way to e...This paper studies a new electron irradiation effect of the formation,movement and growth of stacking fault in YBa_(2) Cu_(3) O_(6+x).The energy of electron irradiation is about 160keV.It would be a promising way to enhance the density of pinning centers.展开更多
The surface growth kinetics of random-like deposition model with two kinds of particles(A and C)is studied.The scaling behavior of the surface width is obtained for various deposition probabilities of particle C and s...The surface growth kinetics of random-like deposition model with two kinds of particles(A and C)is studied.The scaling behavior of the surface width is obtained for various deposition probabilities of particle C and system sizes.We also found a change of different morphologic structures which results from the diffusion of particle C.展开更多
The electronic localization lengthsλof metallic carbon nanotubes with different chiral symmetries have been calculated by one parameter scaling method.It is found thatλis independent of the nanotube chirality,but de...The electronic localization lengthsλof metallic carbon nanotubes with different chiral symmetries have been calculated by one parameter scaling method.It is found thatλis independent of the nanotube chirality,but depends linearly on their diameters.The dependence ofλon the disorder strength W has also been studied,and a power-law relation betweenλand W is also found to be independent of the tube chirality.Our numerical results are in good agreement with recent experimental observations and other theoretical result for only the“armchair”nanotubes.展开更多
GaN/Pb(Zr_(0.53) Ti_(0.47))O_(3) structures have been fabricated by light radiation heating low-pressure metal-organic chemical deposition and pulsed laser deposition. These structures show leakage current lower than ...GaN/Pb(Zr_(0.53) Ti_(0.47))O_(3) structures have been fabricated by light radiation heating low-pressure metal-organic chemical deposition and pulsed laser deposition. These structures show leakage current lower than 10-11 A at applied voltage of 5 V. X-ray diffraction shows that ferroelectric Pb(Zr_(0.53) Ti_(0.47))O_(3) films directly on GaN are well crystallized with perovskite structure. Because of the high thermal stability and relatively smaller mismatch between GaN and ferroelectrics in comparison with that of Si/ferroelectric structures, GaN looks like more promising as semiconductor active layer for metal-ferroelectric-semiconductor field effect transistors.展开更多
Magnetic measurements have been carried out on partial melt(Tl_(0.5)Pb_(0.5))(Ba_(x)Sr_(0.8))_(2)Ca_(2)Cu_(3)O_(y)(x=0.1,0.2)(TI-1223)samples,which indicate that higher melting temperature and longer melting time can ...Magnetic measurements have been carried out on partial melt(Tl_(0.5)Pb_(0.5))(Ba_(x)Sr_(0.8))_(2)Ca_(2)Cu_(3)O_(y)(x=0.1,0.2)(TI-1223)samples,which indicate that higher melting temperature and longer melting time can be used to obtain Tl-1223 compound with better superconducting properties.On the contrary,introducing of Ba vacancy into Tl-1223 samples results in worse superconducting properties.At the end,the power law relationship between the critical current density and the applied field is explained by the flux creep model and the collective pinning theory.展开更多
The electronic structures of small aluminum clusters,Al_(n)(n=5-24),are investigated by a localized-orbital theory based on the tight-binding approximation.Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum,...The electronic structures of small aluminum clusters,Al_(n)(n=5-24),are investigated by a localized-orbital theory based on the tight-binding approximation.Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum,and simultaneously an s-p gap minimum,but not necessarily an ionization potential maximum,where HOMO-LUMO gap denotes the energy gap between the highest occupied orbital and the lowest unoccupied orbital of the cluster.Also revealed is an irregular odd-even alternation in HOMO-LUMO gaps for Al_(n)(n=7-24).Cluster geometry either contributes to or dominates these findings.展开更多
The effective activation energy of one HgBaCaCuO 1223 superconductor as a function of current density was extracted from the magnetic relaxation measurements below 30K,and found to obey a power law.We also obtained ef...The effective activation energy of one HgBaCaCuO 1223 superconductor as a function of current density was extracted from the magnetic relaxation measurements below 30K,and found to obey a power law.We also obtained effective activation energy as a function of current density from the magnetic hysteresis loops(M-H).The data sets for the M-H loops at different temperatures overlap each other,and all fall on the smooth U_(eff)(J,0)curve based solely on the magnetization relaxation measurements.This indicates that the field dependence of magnetic critical current density is determined by the flux creep via nonlinear effective activation energy at low temperatures.展开更多
Magnetic hysteresis loops and magnetization relaxation of a zone-melted Y Ba_(2)Cu_(3)O_(6+x) sample were measured by superconducting quantum interference device(SQUID)at temperature from 4.5 to 70K.The logarithmic be...Magnetic hysteresis loops and magnetization relaxation of a zone-melted Y Ba_(2)Cu_(3)O_(6+x) sample were measured by superconducting quantum interference device(SQUID)at temperature from 4.5 to 70K.The logarithmic behavior of niagnetic decay at 4.5 K and the gritdua,l deviation as the temperature is increased deinon-stra.ted the important role of nonlinea.r current density dependence of effective flux pinning potential U(J)in high temperature supcrconductors.展开更多
Valley,the energy extrema in the electronic band structure at momentum space,is regarded as a new degree of freedom of electrons,in addition to charge and spin.The studies focused on valley degree of freedom now form ...Valley,the energy extrema in the electronic band structure at momentum space,is regarded as a new degree of freedom of electrons,in addition to charge and spin.The studies focused on valley degree of freedom now form an emerging field of condensed-matter physics,i.e.,valleytronics,whose development is exactly following that of spintronics,which focuses on the spin degree of freedom.展开更多
Si is an important material for manufacturing chips of microelectronic integrated circuits and transistors. Special Si devices can be used as the base materials for optical transmitters and detectors. However, as crys...Si is an important material for manufacturing chips of microelectronic integrated circuits and transistors. Special Si devices can be used as the base materials for optical transmitters and detectors. However, as crystalline Si is an indirect band gap material and展开更多
Regulation of optical properties and electronic structure of two-dimensional layered ReS_2 materials has attracted much attention due to their potential in electronic devices.However,the identification of structure tr...Regulation of optical properties and electronic structure of two-dimensional layered ReS_2 materials has attracted much attention due to their potential in electronic devices.However,the identification of structure transformation of monolayer ReS_2 induced by strain is greatly lacking.In this work,the Raman spectra of monolayer ReS_2 with external strain are determined theoretically based on the density function theory.Due to the lower structural symmetry,deformation induced by external strain can only regulate the Raman mode intensity but cannot lead to Raman mode shifts.Our calculations suggest that structural deformation induced by external strain can be identified by Raman scattering.展开更多
Crystal tilts in epitaxially laterally overgrown(ELO)GaN films via hydride vapor phase epitaxy(HVPE)on sapphire substrates have been investigated by using four-circle x-ray diffraction method.Three diffraction peaks c...Crystal tilts in epitaxially laterally overgrown(ELO)GaN films via hydride vapor phase epitaxy(HVPE)on sapphire substrates have been investigated by using four-circle x-ray diffraction method.Three diffraction peaks corresponding to the(0002)reflection of vertically epitaxial and tilted GaN domains are observable in the x-ray rocking curve.The angle separationsΔωbetween the main peak and two lobes change with the azimuth angleФ.The dependence ofΔωonФand the crystal tilt angleθhas been calculated based on the standard kinetic x-ray diffraction model.The crystal tilt angle of a typical HVPE ELO GaN sample has been determined to be 2.379℃.展开更多
Using a double templating method by electroless deposition within a templating organic porous mold,we fabricate a monolayer of hexagonal-close-packed metallic nanoshells,each with a small opening.Light transmission sp...Using a double templating method by electroless deposition within a templating organic porous mold,we fabricate a monolayer of hexagonal-close-packed metallic nanoshells,each with a small opening.Light transmission spectra of the metallic nanoshell arrays are measured,which show transmission resonances at specific wavelengths whose positions are observed to be independent of the incident angle as well as light polarizations.More interestingly,the resonance wavelengths of Mie plasmon modes are also independent of the surrounding medium.Further numerical simulations confirm these transmission resonances and reveal that they are attributed to the excitations of highly localized dipolar,quadrupolar and hexapolar Mie plasmon modes,which are highly confined within metallic nanoshells.展开更多
The rate equation for flux motion in high-T_(c) superconductors is extended to take the contribution of field sweep into account in this work.It is shown that the time and field sweep rate(H)dependence of magnetizatio...The rate equation for flux motion in high-T_(c) superconductors is extended to take the contribution of field sweep into account in this work.It is shown that the time and field sweep rate(H)dependence of magnetization are equivalent approaches to the study of flux creep properties in high-T_(c) superconductors.The agreement of the effective activation energy Ueff(J)extracted from the time relaxation and that from magnetic hysteresis loops measurements on a melt-textured YBa2Cu3O6+x sample supports this extended rate equation for flux motion in high temperature superconductors.展开更多
The effect of slow neutron irradiation at a low Auence of about 10^(8)n/cm^(2) on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy.By comparative study of the def...The effect of slow neutron irradiation at a low Auence of about 10^(8)n/cm^(2) on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy.By comparative study of the defect structures in a given area in one sample,we get evidence for the flux pinning enhancement by low Auence slow neutron irradiation.展开更多
A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric materialis proposed for light trapping.The equifrequency contours(EFC)of silicon-air multilayer photonic crystals within the first b...A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric materialis proposed for light trapping.The equifrequency contours(EFC)of silicon-air multilayer photonic crystals within the first bandgap region are first studied.A zero-group-velocity at the first Brillouin zone boundary along the grating vector is predicted.The propagation constants and eigenfrequencies of the first-order guiding modes are numerically investigated for photonic crystal waveguide structures with a finite thickness.Different frequency components of the guiding modes are found to slov and stop at different thicknesses inside such a tapered waveguide structure.In addition,the time-evolution of a femto-second pulse propagating in the tapered waveguide is also demonstrated.展开更多
The (Bi_(0.9) Pb_(0.13))_(2)Sr_(2)(Ca_(0.98)R_(0.02))_(2)Cu_(3)O_(10+δ) superconductors (R = Sm, Eu, Gd, Dy, Ca) were prepared and the flux pinning effects of all samples were studied using vibrating sample magnetome...The (Bi_(0.9) Pb_(0.13))_(2)Sr_(2)(Ca_(0.98)R_(0.02))_(2)Cu_(3)O_(10+δ) superconductors (R = Sm, Eu, Gd, Dy, Ca) were prepared and the flux pinning effects of all samples were studied using vibrating sample magnetometer. We found that the pinning potential energy U increases but the flux pinning force Fp decreases when the magnetic moment of the rare earth element increases. We believe that this effect may come from the area of normal state resulting from the magnetic moment of the rare earth element which was particularly substituted for the Ca^(2+) ion of our samples.展开更多
文摘[WT]Phase structures, the transport and magnetic properties of the Perovskite-type manganite （La 0.8-xCexSr 0.2） 0.97 MnO3 （x=0～0.26） prepared by La2O3 containing CeO2 with different contents were studied. Experiments show that the compounds consist of a magnetic perovskite phase and non-magnetic CeO2 and Mn3O4. The resistivity and magnetoresistance ratio （MR） of the samples vary with changing x. Their room-temperature MR reaches -3%～-14% at the magnetic field of 1 T. For x=0; x=0.037 and x=0.26 samples, the conductance keeps unchanged basically in a relatively wide temperature range above 600 K, and the result shows that it is feasible for producing SOFC cathode materials with these samples.
文摘The replica trick used in the renormalization group(RG)for the disordered spin systems is discussed.The recursion relations of RG are derived in a more general situation in which the coupling constants can have arbitrary symmetry to the replica indices.It is shown that the random fixed point found by Luther,Grinstein and Lubensky is unstable.This instability implies that the replica symmetry should be broken in the RG for the disordered systems.
基金Supported by the National Center for Research and Development of Superconductivity of Chinathe Foundation for Doctoral Education.
文摘This paper studies a new electron irradiation effect of the formation,movement and growth of stacking fault in YBa_(2) Cu_(3) O_(6+x).The energy of electron irradiation is about 160keV.It would be a promising way to enhance the density of pinning centers.
基金Supported by Ke-Li Fellowshipthe Young Research Foundation of the Committee of the National Education.
文摘The surface growth kinetics of random-like deposition model with two kinds of particles(A and C)is studied.The scaling behavior of the surface width is obtained for various deposition probabilities of particle C and system sizes.We also found a change of different morphologic structures which results from the diffusion of particle C.
基金Supported by a grant from the State Key Program of China,the National Natural Science Foundation of China under Grant Nos.10074026 and 29890212by the Grant RFDP.
文摘The electronic localization lengthsλof metallic carbon nanotubes with different chiral symmetries have been calculated by one parameter scaling method.It is found thatλis independent of the nanotube chirality,but depends linearly on their diameters.The dependence ofλon the disorder strength W has also been studied,and a power-law relation betweenλand W is also found to be independent of the tube chirality.Our numerical results are in good agreement with recent experimental observations and other theoretical result for only the“armchair”nanotubes.
基金Supported by the National Natural Science Foundation of China under Grant Nos.69976014,69636010,69987001 and 69806006and the National High Technology Research&Development Project of China.
文摘GaN/Pb(Zr_(0.53) Ti_(0.47))O_(3) structures have been fabricated by light radiation heating low-pressure metal-organic chemical deposition and pulsed laser deposition. These structures show leakage current lower than 10-11 A at applied voltage of 5 V. X-ray diffraction shows that ferroelectric Pb(Zr_(0.53) Ti_(0.47))O_(3) films directly on GaN are well crystallized with perovskite structure. Because of the high thermal stability and relatively smaller mismatch between GaN and ferroelectrics in comparison with that of Si/ferroelectric structures, GaN looks like more promising as semiconductor active layer for metal-ferroelectric-semiconductor field effect transistors.
文摘Magnetic measurements have been carried out on partial melt(Tl_(0.5)Pb_(0.5))(Ba_(x)Sr_(0.8))_(2)Ca_(2)Cu_(3)O_(y)(x=0.1,0.2)(TI-1223)samples,which indicate that higher melting temperature and longer melting time can be used to obtain Tl-1223 compound with better superconducting properties.On the contrary,introducing of Ba vacancy into Tl-1223 samples results in worse superconducting properties.At the end,the power law relationship between the critical current density and the applied field is explained by the flux creep model and the collective pinning theory.
基金Supported by the National Natural Science Foundation of China under Grants Nos.19574059 and 19634030.
文摘The electronic structures of small aluminum clusters,Al_(n)(n=5-24),are investigated by a localized-orbital theory based on the tight-binding approximation.Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum,and simultaneously an s-p gap minimum,but not necessarily an ionization potential maximum,where HOMO-LUMO gap denotes the energy gap between the highest occupied orbital and the lowest unoccupied orbital of the cluster.Also revealed is an irregular odd-even alternation in HOMO-LUMO gaps for Al_(n)(n=7-24).Cluster geometry either contributes to or dominates these findings.
基金Supported by the National Center for Research and Development on Superconductivity of ChinaNational Foundation for Doctoral Education.
文摘The effective activation energy of one HgBaCaCuO 1223 superconductor as a function of current density was extracted from the magnetic relaxation measurements below 30K,and found to obey a power law.We also obtained effective activation energy as a function of current density from the magnetic hysteresis loops(M-H).The data sets for the M-H loops at different temperatures overlap each other,and all fall on the smooth U_(eff)(J,0)curve based solely on the magnetization relaxation measurements.This indicates that the field dependence of magnetic critical current density is determined by the flux creep via nonlinear effective activation energy at low temperatures.
基金Supported by the National Center for Research and Development on Superconductivity of Cliinathe Foundation for Doctoral Education.
文摘Magnetic hysteresis loops and magnetization relaxation of a zone-melted Y Ba_(2)Cu_(3)O_(6+x) sample were measured by superconducting quantum interference device(SQUID)at temperature from 4.5 to 70K.The logarithmic behavior of niagnetic decay at 4.5 K and the gritdua,l deviation as the temperature is increased deinon-stra.ted the important role of nonlinea.r current density dependence of effective flux pinning potential U(J)in high temperature supcrconductors.
基金This work was supported by the National Key Research and Development Program of China(2017YFA0303403)Shanghai Science and Technology Innovation Action Plan(No.19JC1416700)+1 种基金the NSF of China(No.51572085,11774092)ECNU Multifunctional Platform for Innovation.
文摘Valley,the energy extrema in the electronic band structure at momentum space,is regarded as a new degree of freedom of electrons,in addition to charge and spin.The studies focused on valley degree of freedom now form an emerging field of condensed-matter physics,i.e.,valleytronics,whose development is exactly following that of spintronics,which focuses on the spin degree of freedom.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50972054 and 60636010, and the National Basic Research Program of China under Grant Nos 2006CB921803 and 2010CB934201.
基金Project supported by the National Natural Science Foundation of Chinathe Natural Science Foundation of Jiangsu Province.
文摘Si is an important material for manufacturing chips of microelectronic integrated circuits and transistors. Special Si devices can be used as the base materials for optical transmitters and detectors. However, as crystalline Si is an indirect band gap material and
基金Supported by the National Natural Science Foundation of China under Grant Nos 61264008,61574080 and 61505085
文摘Regulation of optical properties and electronic structure of two-dimensional layered ReS_2 materials has attracted much attention due to their potential in electronic devices.However,the identification of structure transformation of monolayer ReS_2 induced by strain is greatly lacking.In this work,the Raman spectra of monolayer ReS_2 with external strain are determined theoretically based on the density function theory.Due to the lower structural symmetry,deformation induced by external strain can only regulate the Raman mode intensity but cannot lead to Raman mode shifts.Our calculations suggest that structural deformation induced by external strain can be identified by Raman scattering.
基金Supported by the special fund for Major State Basic Research Projects(#G20000683)the National Science Fund for Distinguished Young Scholars(#60025411)+1 种基金the National Natural Science Foundation of China under Grant Nos.69976014,69636010,69806006 and 69987001the National High Technology Research&Development Project of China.
文摘Crystal tilts in epitaxially laterally overgrown(ELO)GaN films via hydride vapor phase epitaxy(HVPE)on sapphire substrates have been investigated by using four-circle x-ray diffraction method.Three diffraction peaks corresponding to the(0002)reflection of vertically epitaxial and tilted GaN domains are observable in the x-ray rocking curve.The angle separationsΔωbetween the main peak and two lobes change with the azimuth angleФ.The dependence ofΔωonФand the crystal tilt angleθhas been calculated based on the standard kinetic x-ray diffraction model.The crystal tilt angle of a typical HVPE ELO GaN sample has been determined to be 2.379℃.
基金Supported by the National Basic Research Program of China(No 2012CB921501)the National Natural Science Foundation of China(Nos 11174137,11104136,11021403,11004146)+1 种基金the Fundamental Research Funds for the Central Universities(No 1115020403)the Priority Academic Program Development(PAPD).
文摘Using a double templating method by electroless deposition within a templating organic porous mold,we fabricate a monolayer of hexagonal-close-packed metallic nanoshells,each with a small opening.Light transmission spectra of the metallic nanoshell arrays are measured,which show transmission resonances at specific wavelengths whose positions are observed to be independent of the incident angle as well as light polarizations.More interestingly,the resonance wavelengths of Mie plasmon modes are also independent of the surrounding medium.Further numerical simulations confirm these transmission resonances and reveal that they are attributed to the excitations of highly localized dipolar,quadrupolar and hexapolar Mie plasmon modes,which are highly confined within metallic nanoshells.
基金Supported by the National Center for Research and Development on Superconductivity of Chinathe Foundation for Doctoral Education。
文摘The rate equation for flux motion in high-T_(c) superconductors is extended to take the contribution of field sweep into account in this work.It is shown that the time and field sweep rate(H)dependence of magnetization are equivalent approaches to the study of flux creep properties in high-T_(c) superconductors.The agreement of the effective activation energy Ueff(J)extracted from the time relaxation and that from magnetic hysteresis loops measurements on a melt-textured YBa2Cu3O6+x sample supports this extended rate equation for flux motion in high temperature superconductors.
基金Supported by the National Center for Research and Development on Superconductivity of China,and the Foundation for Doctoral Education。
文摘The effect of slow neutron irradiation at a low Auence of about 10^(8)n/cm^(2) on the microstructures of Bi-2223 polycrystalline samples was observed by transmission electron microscopy.By comparative study of the defect structures in a given area in one sample,we get evidence for the flux pinning enhancement by low Auence slow neutron irradiation.
基金Supported by the National Basic Research Program of China under Grant No 2007CB613204the National Natural Science Foundation of China under Grant Nos 10734010,50771054 and 10804044the New Century Excellent Talent Project of the Ministry of Education of China under Grant No NCET-09-0453.
文摘A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric materialis proposed for light trapping.The equifrequency contours(EFC)of silicon-air multilayer photonic crystals within the first bandgap region are first studied.A zero-group-velocity at the first Brillouin zone boundary along the grating vector is predicted.The propagation constants and eigenfrequencies of the first-order guiding modes are numerically investigated for photonic crystal waveguide structures with a finite thickness.Different frequency components of the guiding modes are found to slov and stop at different thicknesses inside such a tapered waveguide structure.In addition,the time-evolution of a femto-second pulse propagating in the tapered waveguide is also demonstrated.
文摘The (Bi_(0.9) Pb_(0.13))_(2)Sr_(2)(Ca_(0.98)R_(0.02))_(2)Cu_(3)O_(10+δ) superconductors (R = Sm, Eu, Gd, Dy, Ca) were prepared and the flux pinning effects of all samples were studied using vibrating sample magnetometer. We found that the pinning potential energy U increases but the flux pinning force Fp decreases when the magnetic moment of the rare earth element increases. We believe that this effect may come from the area of normal state resulting from the magnetic moment of the rare earth element which was particularly substituted for the Ca^(2+) ion of our samples.
