The diameters of the ordinary hard bubbles (OHBs) and soft bubbles in epitaxial garnet films are measured under the microscope at various temperatures. It is found that the bubble diameters of OHBs increase with tem...The diameters of the ordinary hard bubbles (OHBs) and soft bubbles in epitaxial garnet films are measured under the microscope at various temperatures. It is found that the bubble diameters of OHBs increase with temperature, and it is concluded that the equilibrium separation between two neighbouring vertical Bloch lines (VBLs) Seq is widened with increasing temperature. At the same time, the results can be understood simply as that there are more VBLs in the domain walls of the first dumbbell domains (IDs) than those in walls of OHBs at the same temperature.展开更多
Co5Sm/Cr bilayer films were deposited on Si and glass slides by means of a Direct-Current(DC)magnetron sputtering system with substrate heating.Magnetic properties measurements show that the sample with glass substrat...Co5Sm/Cr bilayer films were deposited on Si and glass slides by means of a Direct-Current(DC)magnetron sputtering system with substrate heating.Magnetic properties measurements show that the sample with glass substrate has a comparatively large coercivity(Hc=2 141.2 Oe)with a relatively low optimal temperature(Ts=350 ℃).X-ray diffraction patterns indicate that Cr presents a hexagonal-close-packed(hcp)texture on Si,while a body-centered-cubic(bcc)structure on glass substrate,which leads to Co5Sm films having different lattice constants on Si and glass substrates.At their optimal temperature,the grain size of the sample on glass slide is smaller with its size distribution more uniform.Concurrently,the shape of magnetic domain is more regular and ordered.The value of magnetic switching volume(V)for the film on glass is 1.65×10-18 cm3,smaller than that for films on Si.For the film on glass,the magnetization reversal mechanism is mainly influenced by magnetocrystalline anisotropy,the shape of the crystal grain and the stress in the film.展开更多
The chaotic behaviours of a fractional-order generalized Lorenz system and its synchronization are studied in this paper. A new electronic circuit unit to realize fractional-order operator is proposed. According to th...The chaotic behaviours of a fractional-order generalized Lorenz system and its synchronization are studied in this paper. A new electronic circuit unit to realize fractional-order operator is proposed. According to the circuit unit, an electronic circuit is designed to realize a 3.8-order generalized Lorenz chaotic system. Furthermore, synchronization between two fractional-order systems is achieved by utilizing a single-variable feedback method. Circuit experiment simulation results verify the effectiveness of the proposed scheme.展开更多
Powder samples with nominal composition La0.6Sr0.1TexMnO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) were prepared using the sol-gel method with thermal treatment up to 1473 K. On the basis of powder X-ray diffraction (XRD...Powder samples with nominal composition La0.6Sr0.1TexMnO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) were prepared using the sol-gel method with thermal treatment up to 1473 K. On the basis of powder X-ray diffraction (XRD), thermogravimetric and magnetic measurements, it was found that almost all of the Te and a few of the Mn ions were lost from the samples when they were calcined at 1473 K. The reason for the Te loss and a quantitative phase analysis for the samples calcined at 1473 K are discussed in detail.展开更多
We numerically study the dynamics of spiral waves in the excitable system with the excitability modulated by a rectangle wave. The tip trajectories and their variations with the modulation period T are explained by th...We numerically study the dynamics of spiral waves in the excitable system with the excitability modulated by a rectangle wave. The tip trajectories and their variations with the modulation period T are explained by the corre- sponding spectrum analysis. For a large T, the external modulation leads to the occurrence of more frequency peaks and these frequencies change with the modulation period according to their specific rules, respectively. Some of the frequencies and a primary frequency fl determine the corresponding curvature periods, which are locked into rational multiplies of the modulation period. These frequency-locking behaviours and the limited life-span of the frequencies in their variations with the modulation period constitute many resonant entrainment bands in the T axis. In the main bands, which follow the relation T/T12 = m/n, the size variable Rx of the tip trajectory is a monotonic increasing function of T. The rest of the frequencies are linear combinations of the two ones. Due to the complex dynamics, many unique tip trajectories appear at some certain T. We find also that spiral waves are eliminated when T is chosen from the end of the main resonant bands. This offers a useful method of controling the spiral wave.展开更多
Measurement-induced nonlocality(MIN) is a newly defined quantity to measure correlations in bipartite quantum states [Luo S and Fu S 2011 Phys. Rev. Lett. 106 120401]. MIN in the n-qubit W and Greenberger–Horne–Ze...Measurement-induced nonlocality(MIN) is a newly defined quantity to measure correlations in bipartite quantum states [Luo S and Fu S 2011 Phys. Rev. Lett. 106 120401]. MIN in the n-qubit W and Greenberger–Horne–Zeilinger(GHZ) superposition states is considered. It is revealed that n = 3 and n ≥ 4 states have very different characteristics,especially the monogamy relation about MIN, and the monogamy equality of MIN is held in all n-qubit W states(n ≥ 3).展开更多
The low-energy structures and the electronic and the magnetic properties of small NinTin (n : 1-6) and NimTin (1 ≤ n ≤ 4, 1≤m ≤ 4, n ≠m) clusters are investigated by performing all-electron calculations base...The low-energy structures and the electronic and the magnetic properties of small NinTin (n : 1-6) and NimTin (1 ≤ n ≤ 4, 1≤m ≤ 4, n ≠m) clusters are investigated by performing all-electron calculations based on density functional theory. Ground states and several isomers near the ground states are determined for these clusters. The results indicate that the growth of small Ni,nTin clusters prefers to form rich Ti-Ni and Ti Ti bonds. When the percentage of titanium atoms is significantly greater than that of nickel atoms, the nickel atoms are most frequently found above the surface; in contrast, the titanium atoms prefer the bridging sites. A Mulliken spin population analysis indicates that the total spin of titanium-nickel clusters is not always zero.展开更多
We numerically study the dynamics of meandering spiral waves in the excitable system subjected to afeedback signal coming from two measuring points located on a straight line together with the initial spiral core.Thec...We numerically study the dynamics of meandering spiral waves in the excitable system subjected to afeedback signal coming from two measuring points located on a straight line together with the initial spiral core.Thecore location and size radius of the final attractors are computed,and they change with the position of the movingmeasuring point in a unique way.By the Fourier Spectral analysis,we find the frequency-locked behaviors different fromthe driving scheme of the external periodic force.It is also found that the meandering spiral wave can be eliminatedwhen the moving measuring point approaches closely the boundary and its feedback gain is large enough.This offers aneffective and convenient method for eliminating meandering spiral waves.展开更多
We present a scheme for probabilistic dense coding via quantum channels of non-maximally entangled threeparticle states. Quantum dense coding will succeed with a certain probability if the sender introduces an auxilia...We present a scheme for probabilistic dense coding via quantum channels of non-maximally entangled threeparticle states. Quantum dense coding will succeed with a certain probability if the sender introduces an auxiliary particle and performs a collective unitary transformation. The average information transmitted in this scheme is calculated.展开更多
We calculate the energy states and Aharonov Bohm oscillations of an electron in elliptical quantum rings in the presence of a uniform magnetic field by using an exact numerical diagonalization. The calculated results ...We calculate the energy states and Aharonov Bohm oscillations of an electron in elliptical quantum rings in the presence of a uniform magnetic field by using an exact numerical diagonalization. The calculated results show that the elliptical quantum rings are flatter, larger amplitudes and periods of the Aharonov-Bohm oscillations are observed. In addition, in the limits of a circular quantum ring, the results of our approach are in good agreement with those of earlier theories.展开更多
According to the one-dimensional tight-binding Su-Schrieffer-Heeger model, we have investigated the effects of charged polarons on the static polarizability, axx, and the second order hyperpolarizabilities, γxxxx, of...According to the one-dimensional tight-binding Su-Schrieffer-Heeger model, we have investigated the effects of charged polarons on the static polarizability, axx, and the second order hyperpolarizabilities, γxxxx, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su Schrieffer-Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron-electron interactions on αxx and γxxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of αxx and γxxxx increase as the on-site Coulomb interaction U increases for U 〈 Uc and decrease with U for U 〉 Uc, where Uc is a critical value of U at which the static polarizability or the second order hypcrpolarizability reaches a maximal value of αxx or γxxxx. It is found that the effect of the e-e interaction on the value of αxx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γxxxx is sensitive both to the ratio of U to V and to the size of the molecule.展开更多
We study theoretically the essential properties of an exciton in vertically coupled Gaussian quantum dots in the presence of an external magnetic field. The ground state energy of a heavy-hole exciton is split into fo...We study theoretically the essential properties of an exciton in vertically coupled Gaussian quantum dots in the presence of an external magnetic field. The ground state energy of a heavy-hole exciton is split into four energy levels due to the Zeeman effect. For the symmetrical system, the entanglement entropy of the exciton state can reach a value of 1. However, for a system with broken symmetry, it is close to zero. Our results are in good agreement with previous studies.展开更多
Based on the nonlocal nonlinear Schr6dinger equation, the propagation properties of anomalous hollow beams in strongly isotropic nonlocal media are investigated. The analytical expressions of the beam propagation, the...Based on the nonlocal nonlinear Schr6dinger equation, the propagation properties of anomalous hollow beams in strongly isotropic nonlocal media are investigated. The analytical expressions of the beam propagation, the on-axis intensity and the beam width are obt.ained. The results show that the evolution of the beam is periodical and the input power is the most important parameter. The input power determines the variation of the period. Furthermore, it is found that there exists a critical input power in the x direction and in the y direction separately when the initial beam widths in the two transversal directions are unequal. The beam width remains invariant in the corresponding transversal direction when the input power equals the critical power in one of the transversal directions. Selecting a properinput power, the beam can be broadened or compressed in the two transversal directions at the same time, In particular, the beam can be broadened (compressed) in one transversal direction, whereas in the other transversal direction, it is compressed (broadened), i.e., the transversal reverse transformation.展开更多
Transport properties in a multi-terminal regular polygonal quantum ring with Rashba spin-orbit coupling (SOC) are investigated analytically using quantum networks and the transport matrix metLod. The results show th...Transport properties in a multi-terminal regular polygonal quantum ring with Rashba spin-orbit coupling (SOC) are investigated analytically using quantum networks and the transport matrix metLod. The results show that conduc- tances remain at exactly the same values when the output leads are located at axisymmetric positions. However, for the nonaxisymmetrical case, there is a phase difference between the upper and lower arm, which leads to zero conductances appearing periodically. An isotropy of the conductance is destroyed by the Rashba SOC effect in the axisymmetric case. In addition, the position of zero conductance is regulated with the strength of the Rashba SOC.展开更多
We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is ...We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is shown that the entanglement evolution is restricted by a set of monogamy relations. Furthermore, as quantified by the negativity, the entanglement dynamical property of the mixed entangled state of cavity photons is investigated. It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death (ESD). However, compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement, the ESD time of mixed states is later than that of the pure state. Finally, we discuss the entanglement distribution in the multipartite system, and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.展开更多
We propose a scheme for the probabilistic teleportation of an unknown two-particle state of general formation in ion trap. It is shown that one can realize experimentally this teleportation protocol of two-particle st...We propose a scheme for the probabilistic teleportation of an unknown two-particle state of general formation in ion trap. It is shown that one can realize experimentally this teleportation protocol of two-particle state with presently available techniques.展开更多
Using a transfer matrix method, we investigate spin transport through a chain of polygonal rings with Dresselhaus spin-orbit coupling(DSOC). The spin conductance is dependent on the number of sides in the polygons. ...Using a transfer matrix method, we investigate spin transport through a chain of polygonal rings with Dresselhaus spin-orbit coupling(DSOC). The spin conductance is dependent on the number of sides in the polygons. When DSOC is considered in a chain which also has Rashba spin-orbit coupling(RSOC) of the same magnitude, the total conductance is the same as that for the same chain with no SOC. However, when the two types of SOC have different values, there results a unique anisotropic conductance.展开更多
La-deficient La0.77-x Ca0.2SrxMnO3 (0 〈 x 〈 0.1) polycrystalline samples are synthesized using the sol-gel technique. The crystal structures of all the samples are single orthorhombic phase with Pbnm space group. ...La-deficient La0.77-x Ca0.2SrxMnO3 (0 〈 x 〈 0.1) polycrystalline samples are synthesized using the sol-gel technique. The crystal structures of all the samples are single orthorhombic phase with Pbnm space group. Rietveld analysis of x-ray diffraction patterns shows that the Mn-O-Mn bond angle θUn-O-Mn increases whereas the Mn-O bond length dMn--o decreases monotonically with increasing Sr^2+ content, which results in a rich overlap between Mn 3d and O2p orbitals and leads to a systematic increase of the Curie temperature in this compound. It is found that the magnetic entropy change has a maximum at x = 0.06 in La^3+-deficient La0.77-xCa0.2SrxMnO3. This may result from competition between the super-exchange interactions (Mn 4+-O2--Mn4+) and double-exchange interactions (Mn^3+-O^2- -Mn^4+) originating from the appearance of superfluous Mn^4+ ions by substitution of Sr^2+ for La^3+ in this series. Large magnetic entropy changes of 2.32 and 1.83Jkg^-1K^-1 in the x = 0.06 and x = 0.1 samples at their Tcs of 271 K and 303K upon a low magnetic field (10kOe) make these materials promising candidates at near room temperature.展开更多
Anatase TiO_(2) is a promising anode material for lithium-ion batteries(LIBs)owing to its low cost and stability.However,the intrinsically kinetic limits seriously hindered its lithium-ion storage capability.Here we p...Anatase TiO_(2) is a promising anode material for lithium-ion batteries(LIBs)owing to its low cost and stability.However,the intrinsically kinetic limits seriously hindered its lithium-ion storage capability.Here we present that anatase TiO_(2) with rich oxygen vacancies can enhance its lithium-ion storage performance.We synthesize anatase TiO_(2) with well-retained hierarchical structure by annealing the H_(2)Ti_(5)O_(11)·3H_(2)O yolk-shell spheres precursor in nitrogen atmosphere.EPR and XPS data evidence that the oxygen-deficient environment could generate abundant oxygen vacancies in the as-derived anatase TiO_(2),which leads to improved electron conductivity and reduced charge-transfer resistance.The rich oxygen vacancies and high structural integrity of the hierarchical yolk-shell spheres enable the as-derived anatase TiO_(2) yolk-shell spheres with a high specific capacity of 280 mAh g^(-1) at 100 mA g^(-1) and 71%of capacity retention after 5000 cycles at 2 A g^(-1).展开更多
Recently, a stable hollow Sc20C60 cage with Th point group symmetry has been proposed, due to its volleyball- like shape called volleyballene. Here the structural and electronic properties for Sc20C60 cage with a euro...Recently, a stable hollow Sc20C60 cage with Th point group symmetry has been proposed, due to its volleyball- like shape called volleyballene. Here the structural and electronic properties for Sc20C60 cage with a europium atom are further studied based on density functional theory. The results give two stable low-lying Eu@Sc20C60 isomers, called cage-a and cage-b, respectively, which still retain the cage-like shape of Sc20C60 volleyballene. After a Eu atom is encaged into the Sc20C60 volleyballene, the HOMO-LUMO gaps decrease from 1.47eV of the Sc20C60 cage to 0.46 eV of cage-a and 0.21 eV of cage-b. Due to the half-filled 4f-electron orbital states of the Eu atom, the two low-lying Eu@Sc20C60 isomers have net magnetic moments of 7μB. This study further provides the possible applications for the Sc20C60 volleyballene, and enriches the species of magnetic cage-like molecules, which provides more information for magnetic storage and magnetic control.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 10274018, and the Key Foundation of Hebei Normal University under Grant No L2006B10.
文摘The diameters of the ordinary hard bubbles (OHBs) and soft bubbles in epitaxial garnet films are measured under the microscope at various temperatures. It is found that the bubble diameters of OHBs increase with temperature, and it is concluded that the equilibrium separation between two neighbouring vertical Bloch lines (VBLs) Seq is widened with increasing temperature. At the same time, the results can be understood simply as that there are more VBLs in the domain walls of the first dumbbell domains (IDs) than those in walls of OHBs at the same temperature.
基金supported by National Science Foundation of China(10804026)Natural Science Foundation of Hebei Province(E2010000429)Foundation of Hebei Educational Committee(2006123)
文摘Co5Sm/Cr bilayer films were deposited on Si and glass slides by means of a Direct-Current(DC)magnetron sputtering system with substrate heating.Magnetic properties measurements show that the sample with glass substrate has a comparatively large coercivity(Hc=2 141.2 Oe)with a relatively low optimal temperature(Ts=350 ℃).X-ray diffraction patterns indicate that Cr presents a hexagonal-close-packed(hcp)texture on Si,while a body-centered-cubic(bcc)structure on glass substrate,which leads to Co5Sm films having different lattice constants on Si and glass substrates.At their optimal temperature,the grain size of the sample on glass slide is smaller with its size distribution more uniform.Concurrently,the shape of magnetic domain is more regular and ordered.The value of magnetic switching volume(V)for the film on glass is 1.65×10-18 cm3,smaller than that for films on Si.For the film on glass,the magnetization reversal mechanism is mainly influenced by magnetocrystalline anisotropy,the shape of the crystal grain and the stress in the film.
基金supported by the Natural Science Foundation of Hebei Province,China (Grant Nos A2008000136 and A2006000128)
文摘The chaotic behaviours of a fractional-order generalized Lorenz system and its synchronization are studied in this paper. A new electronic circuit unit to realize fractional-order operator is proposed. According to the circuit unit, an electronic circuit is designed to realize a 3.8-order generalized Lorenz chaotic system. Furthermore, synchronization between two fractional-order systems is achieved by utilizing a single-variable feedback method. Circuit experiment simulation results verify the effectiveness of the proposed scheme.
基金supported by the Natural Science Foundation of Hebei Province (No. E2011205083)the Key Item Science Foundation of Hebei Province, China (No.10965125D+3 种基金 No.08965108D)the National Natural Science Foundation of China (No.NSF-10774037No.10074013)the National High Technology Research and Development Program of China (No. 2007AA03Z100)
文摘Powder samples with nominal composition La0.6Sr0.1TexMnO3 (x = 0.00, 0.05, 0.10, 0.15, 0.20) were prepared using the sol-gel method with thermal treatment up to 1473 K. On the basis of powder X-ray diffraction (XRD), thermogravimetric and magnetic measurements, it was found that almost all of the Te and a few of the Mn ions were lost from the samples when they were calcined at 1473 K. The reason for the Te loss and a quantitative phase analysis for the samples calcined at 1473 K are discussed in detail.
基金supported by the National Natural Science Foundation of China (Grant No. 11005030)the Science Foundation of Hebei Education Department,China (Grant No. 2009135)+1 种基金the Science Foundation of Inner Mongolia Education Department,China(Grant No. NJ09178)the Science Foundation of Hebei Normal University,China
文摘We numerically study the dynamics of spiral waves in the excitable system with the excitability modulated by a rectangle wave. The tip trajectories and their variations with the modulation period T are explained by the corre- sponding spectrum analysis. For a large T, the external modulation leads to the occurrence of more frequency peaks and these frequencies change with the modulation period according to their specific rules, respectively. Some of the frequencies and a primary frequency fl determine the corresponding curvature periods, which are locked into rational multiplies of the modulation period. These frequency-locking behaviours and the limited life-span of the frequencies in their variations with the modulation period constitute many resonant entrainment bands in the T axis. In the main bands, which follow the relation T/T12 = m/n, the size variable Rx of the tip trajectory is a monotonic increasing function of T. The rest of the frequencies are linear combinations of the two ones. Due to the complex dynamics, many unique tip trajectories appear at some certain T. We find also that spiral waves are eliminated when T is chosen from the end of the main resonant bands. This offers a useful method of controling the spiral wave.
基金supported by the National Natural Science Foundation of China(Grant Nos.61275215 and 10905016)the National Fundamental Research Program of China(Grant No.2011CBA00203)+1 种基金the Fujian Provincial College Funds for Distinguished Young Scientists,China(Grant No.JA14070)the Natural Science Foundation of Hebei Province,China(Grant No.A2012205062)
文摘Measurement-induced nonlocality(MIN) is a newly defined quantity to measure correlations in bipartite quantum states [Luo S and Fu S 2011 Phys. Rev. Lett. 106 120401]. MIN in the n-qubit W and Greenberger–Horne–Zeilinger(GHZ) superposition states is considered. It is revealed that n = 3 and n ≥ 4 states have very different characteristics,especially the monogamy relation about MIN, and the monogamy equality of MIN is held in all n-qubit W states(n ≥ 3).
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874039)the Natural Science Foundation of Hebei Province of China (Grant Nos. A2009000246 and 2009000243)
文摘The low-energy structures and the electronic and the magnetic properties of small NinTin (n : 1-6) and NimTin (1 ≤ n ≤ 4, 1≤m ≤ 4, n ≠m) clusters are investigated by performing all-electron calculations based on density functional theory. Ground states and several isomers near the ground states are determined for these clusters. The results indicate that the growth of small Ni,nTin clusters prefers to form rich Ti-Ni and Ti Ti bonds. When the percentage of titanium atoms is significantly greater than that of nickel atoms, the nickel atoms are most frequently found above the surface; in contrast, the titanium atoms prefer the bridging sites. A Mulliken spin population analysis indicates that the total spin of titanium-nickel clusters is not always zero.
基金Supported by the National Natural Science Foundation of China under Grant No. 11005030Science Foundations of Hebei Education Department under Grant No. 2009135+1 种基金Science Foundations of Inner Mongolia Education Department under Grant No. NJ09178Science Foundation of Hebei Normal University
文摘We numerically study the dynamics of meandering spiral waves in the excitable system subjected to afeedback signal coming from two measuring points located on a straight line together with the initial spiral core.Thecore location and size radius of the final attractors are computed,and they change with the position of the movingmeasuring point in a unique way.By the Fourier Spectral analysis,we find the frequency-locked behaviors different fromthe driving scheme of the external periodic force.It is also found that the meandering spiral wave can be eliminatedwhen the moving measuring point approaches closely the boundary and its feedback gain is large enough.This offers aneffective and convenient method for eliminating meandering spiral waves.
基金Supported by the National Natural Science Foundation of China under Grant No 10671054, the Natural Science Foundation of Hebei Province under Grant Nos 07M006 and F2009000311, and the Key Project of Science and Technology Research of the Ministry of Education of China under Grant No 207011.
文摘We present a scheme for probabilistic dense coding via quantum channels of non-maximally entangled threeparticle states. Quantum dense coding will succeed with a certain probability if the sender introduces an auxiliary particle and performs a collective unitary transformation. The average information transmitted in this scheme is calculated.
基金Supported by the National Natural Science Foundation of China under Grant No 10674040, the Science and Technology Innovation Foundation of Hebei Province under Grant No 06547006D-4, and the Natural Science Foundation of Hebei Province under Grant No A2007000233.
文摘We calculate the energy states and Aharonov Bohm oscillations of an electron in elliptical quantum rings in the presence of a uniform magnetic field by using an exact numerical diagonalization. The calculated results show that the elliptical quantum rings are flatter, larger amplitudes and periods of the Aharonov-Bohm oscillations are observed. In addition, in the limits of a circular quantum ring, the results of our approach are in good agreement with those of earlier theories.
基金Project supported by the National Natural Science Foundation of China(Grant No.10574037)the Program for New Century Excellent Talents in University of Ministry of Education of China(Grant No.NCET-05-0262)+3 种基金the Hebei Provincial Outstanding Youth Science Fund(Grant No.A2009001512)the Key Project of Ministry of Education of China(Grant No.210021)the Natural Science Fund of Hebei Province,China(Grant No.A2010000357)the Educational Commission of Hebei Province, China(Grant No.2007124)
文摘According to the one-dimensional tight-binding Su-Schrieffer-Heeger model, we have investigated the effects of charged polarons on the static polarizability, axx, and the second order hyperpolarizabilities, γxxxx, of conjugated polymers. Our results are consistent qualitatively with previous ab initio and semi-empirical calculations. The origin of the universal growth is discussed using a local-view formalism that is based on the local atomic charge derivatives. Furthermore, combining the Su Schrieffer-Heeger model and the extended Hubbard model, we have investigated systematically the effects of electron-electron interactions on αxx and γxxxx of charged polymer chains. For a fixed value of the nearest-neighbour interaction V, the values of αxx and γxxxx increase as the on-site Coulomb interaction U increases for U 〈 Uc and decrease with U for U 〉 Uc, where Uc is a critical value of U at which the static polarizability or the second order hypcrpolarizability reaches a maximal value of αxx or γxxxx. It is found that the effect of the e-e interaction on the value of αxx is dependent on the ratio between U and V for either a short or a long charged polymer. Whereas, that effect on the value of γxxxx is sensitive both to the ratio of U to V and to the size of the molecule.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61176089 and 10905016)the Natural Science Foundation of Hebei Province, China (Grant Nos. A2011205092 and A2011208010)
文摘We study theoretically the essential properties of an exciton in vertically coupled Gaussian quantum dots in the presence of an external magnetic field. The ground state energy of a heavy-hole exciton is split into four energy levels due to the Zeeman effect. For the symmetrical system, the entanglement entropy of the exciton state can reach a value of 1. However, for a system with broken symmetry, it is close to zero. Our results are in good agreement with previous studies.
基金supported by the National Natural Science Foundation of China(Grant Nos.61308016,11374089,and 11347121)the Natural Science Foundationof Hebei Province,China(Grant Nos.A2012205023,F2012205076,and A2012205085)+3 种基金the Natural Science Foundation of Hunan Province,China(GrantNo.13JJ4097)the China Postdoctoral Science Foundation(Grant No.2014M551041)the Research Foundation of Education Bureau of Hebei Province,China(Grant No.ZD20131014)Hebei Normal University Foundation,China(Grant No.L2011B06)
文摘Based on the nonlocal nonlinear Schr6dinger equation, the propagation properties of anomalous hollow beams in strongly isotropic nonlocal media are investigated. The analytical expressions of the beam propagation, the on-axis intensity and the beam width are obt.ained. The results show that the evolution of the beam is periodical and the input power is the most important parameter. The input power determines the variation of the period. Furthermore, it is found that there exists a critical input power in the x direction and in the y direction separately when the initial beam widths in the two transversal directions are unequal. The beam width remains invariant in the corresponding transversal direction when the input power equals the critical power in one of the transversal directions. Selecting a properinput power, the beam can be broadened or compressed in the two transversal directions at the same time, In particular, the beam can be broadened (compressed) in one transversal direction, whereas in the other transversal direction, it is compressed (broadened), i.e., the transversal reverse transformation.
基金Project supported by the National Natural Science Foundation of China(Grant No.61176089)Hebei Provincial Natural Science Foundation,China(Grant No.A2011205092)
文摘Transport properties in a multi-terminal regular polygonal quantum ring with Rashba spin-orbit coupling (SOC) are investigated analytically using quantum networks and the transport matrix metLod. The results show that conduc- tances remain at exactly the same values when the output leads are located at axisymmetric positions. However, for the nonaxisymmetrical case, there is a phase difference between the upper and lower arm, which leads to zero conductances appearing periodically. An isotropy of the conductance is destroyed by the Rashba SOC effect in the axisymmetric case. In addition, the position of zero conductance is regulated with the strength of the Rashba SOC.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10905016 and 10971247)the Natural Science Foundation of Hebei Province of China (Grant Nos. A2012205062,A2012205013,and A2010000344)the Fund of Hebei Normal niversity
文摘We analyze the multipartite entanglement evolution of three-qubit mixed states composed of a GHZ state and a W state. For a composite system consisting of three cavities interacting with independent reservoirs, it is shown that the entanglement evolution is restricted by a set of monogamy relations. Furthermore, as quantified by the negativity, the entanglement dynamical property of the mixed entangled state of cavity photons is investigated. It is found that the three cavity photons can exhibit the phenomenon of entanglement sudden death (ESD). However, compared with the evolution of a generalized three-qubit GHZ state which has the equal initial entanglement, the ESD time of mixed states is later than that of the pure state. Finally, we discuss the entanglement distribution in the multipartite system, and point out the intrinsic relation between the ESD of cavity photons and the entanglement sudden birth of reservoirs.
基金Supported by the National Natural Science Foundation of China under Grant No 10971247, and the Hebei Natural Science Foundation of China under Grant No F2009000311.
文摘We propose a scheme for the probabilistic teleportation of an unknown two-particle state of general formation in ion trap. It is shown that one can realize experimentally this teleportation protocol of two-particle state with presently available techniques.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61176089 and 11504083)the Foundation of Shijiazhuang University,China(Grant No.XJPT002)
文摘Using a transfer matrix method, we investigate spin transport through a chain of polygonal rings with Dresselhaus spin-orbit coupling(DSOC). The spin conductance is dependent on the number of sides in the polygons. When DSOC is considered in a chain which also has Rashba spin-orbit coupling(RSOC) of the same magnitude, the total conductance is the same as that for the same chain with no SOC. However, when the two types of SOC have different values, there results a unique anisotropic conductance.
基金Supported by the Key Technologies R& D Programme of Hebei Province under Grant Nos 05547002D and 08965108D, and the the Natural Science Foundation of Hebei Province (E2008000194).
文摘La-deficient La0.77-x Ca0.2SrxMnO3 (0 〈 x 〈 0.1) polycrystalline samples are synthesized using the sol-gel technique. The crystal structures of all the samples are single orthorhombic phase with Pbnm space group. Rietveld analysis of x-ray diffraction patterns shows that the Mn-O-Mn bond angle θUn-O-Mn increases whereas the Mn-O bond length dMn--o decreases monotonically with increasing Sr^2+ content, which results in a rich overlap between Mn 3d and O2p orbitals and leads to a systematic increase of the Curie temperature in this compound. It is found that the magnetic entropy change has a maximum at x = 0.06 in La^3+-deficient La0.77-xCa0.2SrxMnO3. This may result from competition between the super-exchange interactions (Mn 4+-O2--Mn4+) and double-exchange interactions (Mn^3+-O^2- -Mn^4+) originating from the appearance of superfluous Mn^4+ ions by substitution of Sr^2+ for La^3+ in this series. Large magnetic entropy changes of 2.32 and 1.83Jkg^-1K^-1 in the x = 0.06 and x = 0.1 samples at their Tcs of 271 K and 303K upon a low magnetic field (10kOe) make these materials promising candidates at near room temperature.
基金supported by the NationallKey R&D Program of China(2019YFB1503200)the NationallScience Foundation(CBET-1803256)+4 种基金the Anhui ProvinciallNaturallScience Foundation(1908085QB52)the CASHIPS Director’s Fund(YZJJ2018QN21)Shijiazhuang University DoctorallScientific Research Startup Fund Project(20BS019)Colleges and universities in Shandong Province science and technology projects(J17KA097)CAS Key Laboratory of Photovoltaic and Energy Conservation,Chinese Academy of Sciences(PECL2018QN006)。
文摘Anatase TiO_(2) is a promising anode material for lithium-ion batteries(LIBs)owing to its low cost and stability.However,the intrinsically kinetic limits seriously hindered its lithium-ion storage capability.Here we present that anatase TiO_(2) with rich oxygen vacancies can enhance its lithium-ion storage performance.We synthesize anatase TiO_(2) with well-retained hierarchical structure by annealing the H_(2)Ti_(5)O_(11)·3H_(2)O yolk-shell spheres precursor in nitrogen atmosphere.EPR and XPS data evidence that the oxygen-deficient environment could generate abundant oxygen vacancies in the as-derived anatase TiO_(2),which leads to improved electron conductivity and reduced charge-transfer resistance.The rich oxygen vacancies and high structural integrity of the hierarchical yolk-shell spheres enable the as-derived anatase TiO_(2) yolk-shell spheres with a high specific capacity of 280 mAh g^(-1) at 100 mA g^(-1) and 71%of capacity retention after 5000 cycles at 2 A g^(-1).
基金Supported by the National Natural Science Foundation of China under Grant Nos 11274089,U1331116,11304076 and 11547198the Natural Science Foundation of Hebei Province under Grant No A2015205179+2 种基金the Science Foundation of Hebei Education Award for Distinguished Young Scholars under Grant No YQ2013008the Program for High-level Talents of Hebei Province under Grant No A201500118the National Basic Research Program of China under Grant No 2011CB606401
文摘Recently, a stable hollow Sc20C60 cage with Th point group symmetry has been proposed, due to its volleyball- like shape called volleyballene. Here the structural and electronic properties for Sc20C60 cage with a europium atom are further studied based on density functional theory. The results give two stable low-lying Eu@Sc20C60 isomers, called cage-a and cage-b, respectively, which still retain the cage-like shape of Sc20C60 volleyballene. After a Eu atom is encaged into the Sc20C60 volleyballene, the HOMO-LUMO gaps decrease from 1.47eV of the Sc20C60 cage to 0.46 eV of cage-a and 0.21 eV of cage-b. Due to the half-filled 4f-electron orbital states of the Eu atom, the two low-lying Eu@Sc20C60 isomers have net magnetic moments of 7μB. This study further provides the possible applications for the Sc20C60 volleyballene, and enriches the species of magnetic cage-like molecules, which provides more information for magnetic storage and magnetic control.