We propose simple schemes for generating W-type multipartite entangled states in cavity quantum electrodynamics (CQED). Our schemes involve a largely detuned interaction of A-type three-level atoms with a single-mod...We propose simple schemes for generating W-type multipartite entangled states in cavity quantum electrodynamics (CQED). Our schemes involve a largely detuned interaction of A-type three-level atoms with a single-mode cavity field and a classical laser, and both the symmetric and asymmetric W states can be created in a single step. Our schemes are insensitive to both the cavity decay and atomic spontaneous emission. With the above system, we also propose a scheme for realizing quantum-information concentration which is the reverse process of quantum cloning. In this scheme, quantum-information originally coming from a single qubit, but now distributed into many qubits, is concentrated back to a single qubit in onlv one steP.展开更多
The powder X-ray diffraction patterns of LaFell.sSil.5 compounds annealed at different high temperatures from 1323 K (5 h) to 1623 K (2 h) show that a large amount of 1:13 phase begins to form in LaFell.sSiL5 com...The powder X-ray diffraction patterns of LaFell.sSil.5 compounds annealed at different high temperatures from 1323 K (5 h) to 1623 K (2 h) show that a large amount of 1:13 phase begins to form in LaFell.sSiL5 compound annealed at 1423 K (5 h). In the temperature range from 1423 to 1523 K, ^-Fe and LaFeSi phases rapidly decrease to form 1:13 phase. LaFeSi phase is rarely observed, and the most amount of 1:13 phase is obtained in the compound annealed at 1523 K (5 h). With the annealing temperature increasing to 1573 and 1623 K, LaFeSi is detected again in the LaFell.sSil.s compound. According to the results of annealing at different high-temperatures, the Lal-xCexFelt.sSit.5 compounds are annealed at high temperatures of 1373 K (2 h) + 1523 K (5 h). The main phase is NaZn13-type phase, and the impurity is a small amount of et-Fe in Lal-xCexFexx.sSil.5 compounds with 0 〈 x 〈 0.35, and there is a large amount of CeaFe17 phase in Lao.sCeo.sFela.sSil.s. It indicates that the substitution of cerium atoms for La in LaFelLsSil.5 compounds has limit. At the same time, the substitution of Ce for La has large effect on magnetocaloric properties. With increasing Ce content from x = 0 to x = 0.35, the Curie temperature decreases linearly from 196 to 168 K, the magnetic entropy change increases from 16.5 to 57.3 J-kg-kK-1 in a low magnetic field change of 0-2 T, and the thermal hysteresis also increases from 3 K to 8 K.展开更多
We investigate the effect of pump area on lasing modes in an active random medium. Considering the structure characteristics in a real experimental system, the random medium is divided into two regions, i.e. pump and ...We investigate the effect of pump area on lasing modes in an active random medium. Considering the structure characteristics in a real experimental system, the random medium is divided into two regions, i.e. pump and non-pump areas. The dependence of lasing modes on the pump area is qualitatively explained by means of the model in which the lasing is ascribed to the interaction of the complex localized modes in the active random medium with local aperiodic quasi-structure with appropriate pump light. There exist different pump sizes for lasing with different modes. As the pump size decreases in this random system, the pump threshold of the lasing modes increases. There are different lasing modes in different excitation regions in this random system. This gives us some information about the dependence of lasing modes on pump areas in active random media.展开更多
Using a new tortoise coordinate transformation, this paper investigates the Hawking effect from an arbitrarily accelerating charged black hole by the improved Damour-Ruffini method. After the tortoise coordinate trans...Using a new tortoise coordinate transformation, this paper investigates the Hawking effect from an arbitrarily accelerating charged black hole by the improved Damour-Ruffini method. After the tortoise coordinate transformation, the Klein-Gordon equation can be written as the standard form at the event horizon. Then extending the outgoing wave from outside to inside of the horizon analytically, the surface gravity and Hawking temperature can be obtained automatically. It is found that the Hawking temperatures of different points on the surface are different. The quantum nonthermal radiation characteristics of a black hole near the event horizon is also discussed by studying the Hamilton-Jacobi equation in curved spacetime and the maximum overlap of the positive and negative energy levels near the event horizon is given. There is a dimensional problem in the standard tortoise coordinate and the present results may be more reasonable.展开更多
Telecloning and its reverse process, referred to as remote quantum-information concentration (RQIC), have been attracting considerable interest because of their potential applications in quantum-information processing...Telecloning and its reverse process, referred to as remote quantum-information concentration (RQIC), have been attracting considerable interest because of their potential applications in quantum-information processing. The previous RQIC protocols were focused on the reverse process of the optimal universal telecloning. We here study the reverse process of ancilla-free phase-covariant telecloning (AFPCT). It is shown that the quantum information originally distributed into two spatially separated qubits from a single qubit via the optimal AFPCT procedure can be remotely concentrated back to a single qubit with a certain probability by using an asymmetric W state as the quantum channel.展开更多
In this paper, we have reported an investigation on the evolution of nitrogen structures in diamond crystals which contain nitrogen donor atoms in the range of 1500 ppm-1600 ppm following an annealing treatment at a h...In this paper, we have reported an investigation on the evolution of nitrogen structures in diamond crystals which contain nitrogen donor atoms in the range of 1500 ppm-1600 ppm following an annealing treatment at a high pressure of about 6.5 GPa and high temperatures of 1920 K-2120 K. The annealing treatment was found to completely transform nitrogen atoms originally arranged in a single substitutional form (C-center), into a pair form (A-center), indicated from infrared (IR) spectra. The photoluminescence (PL) spectra revealed that a small fraction of nitrogen atoms remained in C-center form, while some nitrogen atoms in A-center form were further transformed into N3 and H3 center structures. In addition, PL spectra have revealed the existence of two newly observed nitrogen-related structures with zero phonon lines at 611 nm and 711 nm. All these findings above are very helpful in understanding the formation mechanism of natural diamond stones of the Ia-type, which contains nitrogen atoms in an aggregated form.展开更多
The colourless IaA-type gem-quality diamond crystals containing a high concentration of nitrogen(1500–1700 ppm)were successfully prepared by annealing the as-grown Ib-type N-doped diamonds at a high temperature and h...The colourless IaA-type gem-quality diamond crystals containing a high concentration of nitrogen(1500–1700 ppm)were successfully prepared by annealing the as-grown Ib-type N-doped diamonds at a high temperature and high pressure in China-type cubic anvil high-pressure apparatus.Experiments were carried out at pressures of 6.5–7.0 GPa and temperatures from 1900 K to 2100 K.Annealing treatment on high-level N-doped diamond crystals shows that the colour of the diamond crystals is obviously reduced from green to colourless after annealing treatment within 1 h at a higher temperature,which is induced by nitrogen aggregation in the diamond lattice indicated by infrared(IR)spectroscopy.It is further revealed that active energy of the nitrogen atom transforming from the dispersed form to the aggregated form is much lower than that in the standard Ib-type diamond crystals with nitrogen concentration less than 300 ppm.The colourless IaA-type diamond crystal prepared by annealing at 2100 K displays the same properties in IR spectra as the high-quality natural diamonds which are classified into the IaA type.展开更多
We present explicit unitary transformations for realizing both symmetric and asymmetric one-to-many economical phase-covariant clonings of qudits. We also propose a corresponding telecloning scheme. It is shown that t...We present explicit unitary transformations for realizing both symmetric and asymmetric one-to-many economical phase-covariant clonings of qudits. We also propose a corresponding telecloning scheme. It is shown that the fidelity of the telecloning with nonmaximally entangled states can be larger than that of the corresponding cloning. This implies that partially entangled states can be better than the maximally entangled states for our economical phase-covariant telecloning scheme.展开更多
We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of...We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of the Si6 cluster is a square bipyramid, and the corresponding melting temperature is about 1923 K. In the heating procedure, the structures of the Si6 cluster change from high symmetry structures containing 5-8 bonds, via prolate structures containing 3-4 bonds, to oblate structures containing 1-2 bonds.展开更多
Using a new tortoise coordinate transformation,we discuss the quantum nonthermal radiation characteristics near an event horizon by studying the Hamilton-Jacobi equation of a scalar particle in curved space-time,and o...Using a new tortoise coordinate transformation,we discuss the quantum nonthermal radiation characteristics near an event horizon by studying the Hamilton-Jacobi equation of a scalar particle in curved space-time,and obtain the event horizon surface gravity and the Hawking temperature on that event horizon.The results show that there is a crossing of particle energy near the event horizon.We derive the maximum overlap of the positive and negative energy levels.It is also found that the Hawking temperature of a black hole depends not only on the time,but also on the angle.There is a problem of dimension in the usual tortoise coordinate,so the present results obtained by using a correct-dimension new tortoise coordinate transformation may be more reasonable.展开更多
This paper proposes a simple scheme for realizing one-qubit and two-qubit quantum gates as well as multiqubit entanglement based on de-SQUID charge qubits through the control of their coupling to a 1D transmission lin...This paper proposes a simple scheme for realizing one-qubit and two-qubit quantum gates as well as multiqubit entanglement based on de-SQUID charge qubits through the control of their coupling to a 1D transmission line resonator (TLR). The TLR behaves effectively as a quantum data-bus mode of a harmonic oscillator, which has several practical advantages including strong coupling strength, reproducibility, immunity to 1/f noise, and suppressed spontaneous emission. In this protocol, the data-bus does not need to stay adiabatically in its ground state, which results in not only fast quantum operation, hut also high-fidelity quantum information processing. Also, it elaborates the transfer process with the 1D transmission line.展开更多
Absorption spectra for Sn clusters (n=2...8) are calculated using an adiabatic time-dependent density functional formalism within the local density approximation (LDA). We compare the calculated spectra with those...Absorption spectra for Sn clusters (n=2...8) are calculated using an adiabatic time-dependent density functional formalism within the local density approximation (LDA). We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA (TDLDA) spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higherorder finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the 'hard sphere' model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations.展开更多
In this paper, we present a combination method of constructing the explicit and exact solutions of nonlinear partial differential equations. And as an illustrative example, we apply the method to the Benney-Kawahara-L...In this paper, we present a combination method of constructing the explicit and exact solutions of nonlinear partial differential equations. And as an illustrative example, we apply the method to the Benney-Kawahara-Lin equation and derive its many explicit and exact solutions which are all new solutions.展开更多
We present a scheme for generating four pairs of two-atom Einstein Podolsky-Rosen (EPR) states using the simultaneous interaction of the two atoms with a single-mode cavity field under a large detuning condition. Th...We present a scheme for generating four pairs of two-atom Einstein Podolsky-Rosen (EPR) states using the simultaneous interaction of the two atoms with a single-mode cavity field under a large detuning condition. The influence of cavity dissipation on the prepared EPR states is investigated by means of the superoperator method and the state fidelity. It is shown that some kinds of the prepared EPR states are robust against cavity dissipation and the intensity of the field, and maintain their entanglement invariance, and the others are fragile and completely destroyed by the action of cavity dissipation and the intensity of the field in the long-time limit. Decoherence time of the fragile entangled states is extremely small for a typical cavity-QED experimental data.展开更多
5-at% Mn-doped and undoped BaTiO3 thin films have been grown under different oxygen partial pressures by Pulsed Laser Deposition (PLD) on platinum-coated sapphire substrates. X-ray diffraction (XRD) measurements f...5-at% Mn-doped and undoped BaTiO3 thin films have been grown under different oxygen partial pressures by Pulsed Laser Deposition (PLD) on platinum-coated sapphire substrates. X-ray diffraction (XRD) measurements for all the thin films reveal a similar polycrystalline single-phase perovskite structure. Ferroelectricity is observed in the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Ferromagnetic coupling of the Mn dopant ions, on the other hand, is only seen in Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure in a wide temperature range from 5 K to 300 K, and is attributed to the enhanced exchange coupling between Mn dopants and electrons at oxygen vacancies. Our results show that the leakage current is decreased with the doped Mn, but increases the dielectric loss and decreases the dielectric constant, and the ferroelectricity is impaired. To produce ferromagnetism, oxygen vacancies are necessary, which unfortunately increase the leakage current. This confirms that the mutual interplay between the ferroelectricity and ferromagnetism can be tuned by exchange coupling of the doped-Mn and oxygen vacancies in the BaTiO3 thin films.展开更多
The approximate analytical expressions of the apertured broadband beams in the far field with Gaussian and Laguerre-Gaussian spatial modes are presented. For the radially polarized Laguerre-Gaussian beam, the result r...The approximate analytical expressions of the apertured broadband beams in the far field with Gaussian and Laguerre-Gaussian spatial modes are presented. For the radially polarized Laguerre-Gaussian beam, the result reveals that the electromagnetic field in the far field is transverse magnetic. The influences of bandwidth (Г) and truncation parameter (Co) on the transverse intensity distribution of the Gaussian beam and on the energy flux distribution of radially polarized Laguerre-Gaussian beam are analysed.展开更多
A ZnO layer with rather good crystalline quality(Xmin=9.4%)is grown on a sapphire substrate by plasma enhanced chemical vapor deposition(PECVD).Rutherford backscattering(RBS)/channeling and high-resolution x-ray diffr...A ZnO layer with rather good crystalline quality(Xmin=9.4%)is grown on a sapphire substrate by plasma enhanced chemical vapor deposition(PECVD).Rutherford backscattering(RBS)/channeling and high-resolution x-ray diffraction(XRD)are used to characterize the elastic strain in the ZnO epilayer.The tetragonal distortion is positive and depth dependent.It is highest near the interface and decreases towards the sample surface.By combining the results of RBS and XRD,the average elastic strains in the parallel and the perpendicular directions can be calculated to be 0.50%and-0.17%,respectively.展开更多
基金Project supported by the Key Scientific Research Fund of the Educational Department of Hunan Province of China (Grant No. 09A013)Science Foundation of Hengyang Normal University of China (Grant No. 09A28)
文摘We propose simple schemes for generating W-type multipartite entangled states in cavity quantum electrodynamics (CQED). Our schemes involve a largely detuned interaction of A-type three-level atoms with a single-mode cavity field and a classical laser, and both the symmetric and asymmetric W states can be created in a single step. Our schemes are insensitive to both the cavity decay and atomic spontaneous emission. With the above system, we also propose a scheme for realizing quantum-information concentration which is the reverse process of quantum cloning. In this scheme, quantum-information originally coming from a single qubit, but now distributed into many qubits, is concentrated back to a single qubit in onlv one steP.
基金supported by the Key Project of National Natural Science Foundation of China (No. 50731007)the National High-Tech Research and Development Program of China (No. 2007AA03Z440)
文摘The powder X-ray diffraction patterns of LaFell.sSil.5 compounds annealed at different high temperatures from 1323 K (5 h) to 1623 K (2 h) show that a large amount of 1:13 phase begins to form in LaFell.sSiL5 compound annealed at 1423 K (5 h). In the temperature range from 1423 to 1523 K, ^-Fe and LaFeSi phases rapidly decrease to form 1:13 phase. LaFeSi phase is rarely observed, and the most amount of 1:13 phase is obtained in the compound annealed at 1523 K (5 h). With the annealing temperature increasing to 1573 and 1623 K, LaFeSi is detected again in the LaFell.sSil.s compound. According to the results of annealing at different high-temperatures, the Lal-xCexFelt.sSit.5 compounds are annealed at high temperatures of 1373 K (2 h) + 1523 K (5 h). The main phase is NaZn13-type phase, and the impurity is a small amount of et-Fe in Lal-xCexFexx.sSil.5 compounds with 0 〈 x 〈 0.35, and there is a large amount of CeaFe17 phase in Lao.sCeo.sFela.sSil.s. It indicates that the substitution of cerium atoms for La in LaFelLsSil.5 compounds has limit. At the same time, the substitution of Ce for La has large effect on magnetocaloric properties. With increasing Ce content from x = 0 to x = 0.35, the Curie temperature decreases linearly from 196 to 168 K, the magnetic entropy change increases from 16.5 to 57.3 J-kg-kK-1 in a low magnetic field change of 0-2 T, and the thermal hysteresis also increases from 3 K to 8 K.
基金Supported by the National Natural Science Foundation of China under Grant Nos 60278016 and 10464002.
文摘We investigate the effect of pump area on lasing modes in an active random medium. Considering the structure characteristics in a real experimental system, the random medium is divided into two regions, i.e. pump and non-pump areas. The dependence of lasing modes on the pump area is qualitatively explained by means of the model in which the lasing is ascribed to the interaction of the complex localized modes in the active random medium with local aperiodic quasi-structure with appropriate pump light. There exist different pump sizes for lasing with different modes. As the pump size decreases in this random system, the pump threshold of the lasing modes increases. There are different lasing modes in different excitation regions in this random system. This gives us some information about the dependence of lasing modes on pump areas in active random media.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10873003 and 11045005)the Natural Science Foundation of Zhejiang Province,China (Grant No. Y6090739)
文摘Using a new tortoise coordinate transformation, this paper investigates the Hawking effect from an arbitrarily accelerating charged black hole by the improved Damour-Ruffini method. After the tortoise coordinate transformation, the Klein-Gordon equation can be written as the standard form at the event horizon. Then extending the outgoing wave from outside to inside of the horizon analytically, the surface gravity and Hawking temperature can be obtained automatically. It is found that the Hawking temperatures of different points on the surface are different. The quantum nonthermal radiation characteristics of a black hole near the event horizon is also discussed by studying the Hamilton-Jacobi equation in curved spacetime and the maximum overlap of the positive and negative energy levels near the event horizon is given. There is a dimensional problem in the standard tortoise coordinate and the present results may be more reasonable.
文摘Telecloning and its reverse process, referred to as remote quantum-information concentration (RQIC), have been attracting considerable interest because of their potential applications in quantum-information processing. The previous RQIC protocols were focused on the reverse process of the optimal universal telecloning. We here study the reverse process of ancilla-free phase-covariant telecloning (AFPCT). It is shown that the quantum information originally distributed into two spatially separated qubits from a single qubit via the optimal AFPCT procedure can be remotely concentrated back to a single qubit with a certain probability by using an asymmetric W state as the quantum channel.
基金Project supported by the Natural Science Foundation of Heilongjiang Province,China(Grant No.E201341)the Open Research Program of Key Lab of Superhard Materials of Mudanjiang Normal College,China(Grant No.201302)
文摘In this paper, we have reported an investigation on the evolution of nitrogen structures in diamond crystals which contain nitrogen donor atoms in the range of 1500 ppm-1600 ppm following an annealing treatment at a high pressure of about 6.5 GPa and high temperatures of 1920 K-2120 K. The annealing treatment was found to completely transform nitrogen atoms originally arranged in a single substitutional form (C-center), into a pair form (A-center), indicated from infrared (IR) spectra. The photoluminescence (PL) spectra revealed that a small fraction of nitrogen atoms remained in C-center form, while some nitrogen atoms in A-center form were further transformed into N3 and H3 center structures. In addition, PL spectra have revealed the existence of two newly observed nitrogen-related structures with zero phonon lines at 611 nm and 711 nm. All these findings above are very helpful in understanding the formation mechanism of natural diamond stones of the Ia-type, which contains nitrogen atoms in an aggregated form.
基金Supported by the National Natural Science Foundation of China under Grant No 51172089.
文摘The colourless IaA-type gem-quality diamond crystals containing a high concentration of nitrogen(1500–1700 ppm)were successfully prepared by annealing the as-grown Ib-type N-doped diamonds at a high temperature and high pressure in China-type cubic anvil high-pressure apparatus.Experiments were carried out at pressures of 6.5–7.0 GPa and temperatures from 1900 K to 2100 K.Annealing treatment on high-level N-doped diamond crystals shows that the colour of the diamond crystals is obviously reduced from green to colourless after annealing treatment within 1 h at a higher temperature,which is induced by nitrogen aggregation in the diamond lattice indicated by infrared(IR)spectroscopy.It is further revealed that active energy of the nitrogen atom transforming from the dispersed form to the aggregated form is much lower than that in the standard Ib-type diamond crystals with nitrogen concentration less than 300 ppm.The colourless IaA-type diamond crystal prepared by annealing at 2100 K displays the same properties in IR spectra as the high-quality natural diamonds which are classified into the IaA type.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11004050 and 10874019.
文摘We present explicit unitary transformations for realizing both symmetric and asymmetric one-to-many economical phase-covariant clonings of qudits. We also propose a corresponding telecloning scheme. It is shown that the fidelity of the telecloning with nonmaximally entangled states can be larger than that of the corresponding cloning. This implies that partially entangled states can be better than the maximally entangled states for our economical phase-covariant telecloning scheme.
基金Supported by the National Natural Science Foundation of China under Grant No 10274055, the Natural Science Foundation of Sichuan Education Bureau under Grant No 2004A181, and the Research Fund for the Doctoral Program of Yibin University under Grant No 2005B01.
文摘We investigate the structures and the melting temperature of the Si6 cluster by using the first-principles pseudopotential method in real space and Langevin molecular dynamics. It is shown that the ground structure of the Si6 cluster is a square bipyramid, and the corresponding melting temperature is about 1923 K. In the heating procedure, the structures of the Si6 cluster change from high symmetry structures containing 5-8 bonds, via prolate structures containing 3-4 bonds, to oblate structures containing 1-2 bonds.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10873003,11045005,and 11273009)the Natural Science Foundation of Zhejiang Province,China (Grant No. Y6090739)
文摘Using a new tortoise coordinate transformation,we discuss the quantum nonthermal radiation characteristics near an event horizon by studying the Hamilton-Jacobi equation of a scalar particle in curved space-time,and obtain the event horizon surface gravity and the Hawking temperature on that event horizon.The results show that there is a crossing of particle energy near the event horizon.We derive the maximum overlap of the positive and negative energy levels.It is also found that the Hawking temperature of a black hole depends not only on the time,but also on the angle.There is a problem of dimension in the usual tortoise coordinate,so the present results obtained by using a correct-dimension new tortoise coordinate transformation may be more reasonable.
基金The project supported by the Natural Science Foundation of Hunan Province under Grant No. 06jj50014, Key Project Foundation of the Education Commission of Hunan Province under Grant No. 06A055 and National Natural Science Foundation of China under Grant No. 10574126
基金supported by Hunan Provincial Natural Science Foundation of China (Grant No 06JJ50014)the Key Project Foundation of the Education Commission of Hunan Province of China (Grant No 06A055)
文摘This paper proposes a simple scheme for realizing one-qubit and two-qubit quantum gates as well as multiqubit entanglement based on de-SQUID charge qubits through the control of their coupling to a 1D transmission line resonator (TLR). The TLR behaves effectively as a quantum data-bus mode of a harmonic oscillator, which has several practical advantages including strong coupling strength, reproducibility, immunity to 1/f noise, and suppressed spontaneous emission. In this protocol, the data-bus does not need to stay adiabatically in its ground state, which results in not only fast quantum operation, hut also high-fidelity quantum information processing. Also, it elaborates the transfer process with the 1D transmission line.
基金Project supported by the National Natural Science Foundation of China (Grant No 10274055), the Natural Science Foundation of Sichuan Education Bureau, China (Grant No 2004A181) and the Research Fund for the Doctoral Program of Yibin University, China (Grant No 2005B01).
文摘Absorption spectra for Sn clusters (n=2...8) are calculated using an adiabatic time-dependent density functional formalism within the local density approximation (LDA). We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA (TDLDA) spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higherorder finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the 'hard sphere' model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO-LUMO gaps and the geometrical configurations.
基金Project supported by the National Natural Science Foundation of China (Grant No 10672053)
文摘In this paper, we present a combination method of constructing the explicit and exact solutions of nonlinear partial differential equations. And as an illustrative example, we apply the method to the Benney-Kawahara-Lin equation and derive its many explicit and exact solutions which are all new solutions.
基金Supported by the Natural Science Foundation of the Education Department of Hunan Province under Grant No 05C696.
文摘We present a scheme for generating four pairs of two-atom Einstein Podolsky-Rosen (EPR) states using the simultaneous interaction of the two atoms with a single-mode cavity field under a large detuning condition. The influence of cavity dissipation on the prepared EPR states is investigated by means of the superoperator method and the state fidelity. It is shown that some kinds of the prepared EPR states are robust against cavity dissipation and the intensity of the field, and maintain their entanglement invariance, and the others are fragile and completely destroyed by the action of cavity dissipation and the intensity of the field in the long-time limit. Decoherence time of the fragile entangled states is extremely small for a typical cavity-QED experimental data.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10875004 and 11005005)the National Basic Research Program of China (Grant No. 2010CB832904)
文摘5-at% Mn-doped and undoped BaTiO3 thin films have been grown under different oxygen partial pressures by Pulsed Laser Deposition (PLD) on platinum-coated sapphire substrates. X-ray diffraction (XRD) measurements for all the thin films reveal a similar polycrystalline single-phase perovskite structure. Ferroelectricity is observed in the Mn-doped and undoped BaTiO3 thin films grown under relatively high oxygen partial pressure. Ferromagnetic coupling of the Mn dopant ions, on the other hand, is only seen in Mn-doped BaTiO3 thin films prepared under low oxygen partial pressure in a wide temperature range from 5 K to 300 K, and is attributed to the enhanced exchange coupling between Mn dopants and electrons at oxygen vacancies. Our results show that the leakage current is decreased with the doped Mn, but increases the dielectric loss and decreases the dielectric constant, and the ferroelectricity is impaired. To produce ferromagnetism, oxygen vacancies are necessary, which unfortunately increase the leakage current. This confirms that the mutual interplay between the ferroelectricity and ferromagnetism can be tuned by exchange coupling of the doped-Mn and oxygen vacancies in the BaTiO3 thin films.
基金supported by the Doctorial Start-up Fund of Hengyang Normal University,China (Grant No. 09B06)the Natural Science Foundation of Hunan Province,China (Grant No. 08jj3001)
文摘The approximate analytical expressions of the apertured broadband beams in the far field with Gaussian and Laguerre-Gaussian spatial modes are presented. For the radially polarized Laguerre-Gaussian beam, the result reveals that the electromagnetic field in the far field is transverse magnetic. The influences of bandwidth (Г) and truncation parameter (Co) on the transverse intensity distribution of the Gaussian beam and on the energy flux distribution of radially polarized Laguerre-Gaussian beam are analysed.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50802041 and 50872050the National Basic Research Program of China under Grant No 2010CB831524+1 种基金the 2009 Self-Raised Funds Project of Langfang Science and Technology Bureau under Grant No 2009013056the 2011 Key Project of the Langfang Teachers College under Grant No LSZZ201101.
文摘A ZnO layer with rather good crystalline quality(Xmin=9.4%)is grown on a sapphire substrate by plasma enhanced chemical vapor deposition(PECVD).Rutherford backscattering(RBS)/channeling and high-resolution x-ray diffraction(XRD)are used to characterize the elastic strain in the ZnO epilayer.The tetragonal distortion is positive and depth dependent.It is highest near the interface and decreases towards the sample surface.By combining the results of RBS and XRD,the average elastic strains in the parallel and the perpendicular directions can be calculated to be 0.50%and-0.17%,respectively.