Energy Spectrum of Ground State and Excitation Spectrum of Quasi-particle for Hard-Core Boson in Optical Lattices

We investigate the energy spectrum of ground state and quasi-particle excitation spectrum of hard-core bosons, which behave very much like spinless noninteracting ferrnions, in optical lattices by means of the perturbation expansion and Bogoliubov approach. The results show that the energy spectrum has a single band structure, and the energy is lower near zero momentum; the excitation spectrum gives corresponding energy gap, and the system is in Mort-insulating state at Tonks limit. The analytic result of energy spectrum is in good agreement with that calculated in terms of Green＇s function at strong correlation limit.     

Excitation Spectrum of Spin-1 Bosonic Atoms in an Optical Lattice with High Filling Factors

The Green＇s function and the higher-order correlation functions of spin-1 cold atoms in an optical lattice are defined. Because we consider the problem of spin-1 Bose condensed atoms in an optical lattice with high filling factors, i.e., the number density of Bose condensed atoms no is large, the fluctuation of them can be neglected and we take mean-field approximation for the higher-order terms. The excitation spectra for both the polar case and the ferromagnetic case are obtained and analyzed.     

Energy Spectrum of Two-Component Bose-Einstein Condensates in Optical Lattices

With the method of Green's function, we investigate the energy spectra of two-component ultracold bosonic atoms in optical lattices. We find that there are two energy bands for each component. The critical condition of the superfluid-Mott insulator phase transition is determined by the energy band structure. We also find that the nearest neighboring and on-site interactions fail to change the structure of energy bands, but shift the energy bands only. According to the conditions of the phase transitions, three stable superfluid and Mott insulating phases can be found by adjusting the experiment parameters. We also discuss the possibility of observing these new phases and their transitions in further experiments.     

Light-Induced Hofstadter＇s Butterfly Spectrum in Optical Lattices

We propose a scheme to create an effective magnetic field, which can be perceived by cold neutral atoms in a two-dimensional optical lattice, with a laser field with a space-dependent phase and a conventional laser field acting on A-type three-level atoms. When the dimensionless parameter a, being the ratio of flux through a lattice cell to one flux quantum, is rational, the energy spectrum shows a fractal band structure, which is so-called Hofstadter＇s butterfly.     

Unified Solutions of the Hard-Core Fermi-and Bose-Hubbard Models

A unified algebraic approach to both the hard-core Fermi- and Bose-Hubbard models is extended to boththe finite- and infinite-site with periodic condition cases. Excitation energies and the corresponding wavefunctions ofboth the models with nearest neighbor hopping are exactly derived by using a new and simple algebraic method. It isfound that spectra of both the models are determined simply by eigenvalue problem of N × N hopping matrix, where Nis the number of sites for finite system or the period of sites for infinite system.     

Energy Conditions of Charged Boson Condensate and Degenerate Fermions

We study the energy conditions of a relativistic λΦ⁴ self-interact& charged boson condensate coupled to degenerate fermions. It is found that strong energy condition will be violated within certain range of the mass parameters and the coupling constants in the model.     

Spin Accumulation of Spinor Atoms in Optical Lattices

We obtain an effective spin correlation Hamiltonian describing the interaction of light with a two-level atom, then we investigate the classical trajectory of the two-level atom system by numerical integration of the Heisenberg equation of motion. Our results show that the spin accumulation is a very popular phenomenon as long as the spin character cannot be ignored in the Hamiltonian. We propose experimental protocol to observe this new phenomenon in further experiments.     

Bose-Einstein Condensates in Optical Lattices with Higher-Order Interactions

The higher-order interactions of Bose-Einstein condensate in multi-dimensional optical lattices are discussed both analytically and numerically.It is demonstrated that the effects of the higher-order atomic interactions on the sound speed and the stabilities of Bloch waves strongly depend on the lattice strength.In the presence of higher-order effects,tighter and high-dimensional lattices are confirmed to be two positive factors for maintaining the system's energetic stability,and the dynamical instability of Bloch waves can take place simultaneously with the energetic instability.In addition,we find that the higher-order interactions exhibit a long-range behavior and the long-lived coherent Bloch oscillations in a tilted optical lattice exist.Our results provide an effective way to probe the higher-order interactions in optical lattices.     

Chaotic Ratchet Effect for Bose-Einstein Condensed Atoms in 1D Optical Lattices

The chaotic ratchet effect for Bos-Einstein condensed atoms in an optical lattice is investigated. By using the direct perturbation method we obtain the chaotic solution of the condensed system. Theoretical analysis reveals that the transport of the condensed atoms in the ratchet potential is a chaotic one, and corresponding numerical results agree well with the theoretical results.     

Chaotic Ratchet Effect for Bose-Einstein Condensed Atoms in 1D Optical Lattices

The chaotic ratchet effect for Bose-Einstein condensed atoms in an optical lattice is investigated. By using the direct perturbation method we obtain the chaotic solution of the condensed system. Theoretical analysis reveals that the transport of the condensed atoms in the ratchet potential is a chaotic one, and corresponding numerical results agree well with the theoretical results.     

Landau-Zener Tunnelling of Two-Component Bose-Einstein Condensates in Optical Lattices

We investigate the Landau-Zener tunnelling of two-component Bose-Einstein condensates （BECs） in optical lattices. In the neighborhood of the Brillouin zone edge, the system can be reduced to two coupled nonlinear two-level models. From the models, we calculate the change of the tunnelling probability for each component with the linear sweeping rate. It is found that the probability for each component exhibits regular oscillating behavior for the larger sweeping rate, but for smaller rate the oscillation is irregular. Moreover, the asymmetry of the tunnelling between the two components can be induced by the unbalanced initial populations or the inequality of the two self-interactions when the cross-interaction between the components exists. The result can not be found in the single component BECs.     

Properties of Controllable Soliton Switching in Optical Lattices with Longitudinal Exponential-Asymptotic Modulation

The properties of controllable soliton switching in Kerr-type optical lattices with different modulation are investigated theoretically and simulated numerically. The results show that the optical lattices can be available for all-optical soliton switching through utilization for length-scale competition effects. And through longitudinal exponential-asymptotic modulation for the linear refractive index, the properties of soliton switching in the optical lattices can be improved. The number of output channels of soliton switching can be controlled by the parameters such as incident angle, asymptotic rate of longitudinal modulation, guiding parameter and form factor.     

激发源光谱宽度对其辐射通量转换效率的影响

为了进一步提高固态照明中荧光转换光源(PC-LED)的白光发射效率,探寻激发源与荧光粉搭配对合成白光辐射通量转换效率之间的关系。以YAG荧光粉为对象,搭配不同光谱宽度的激发源,采用光谱计算方法研究了合成白光光源中激发源光谱宽度对其辐射通量转换效率的影响,计算结果通过实验进行了验证。结果表明:当光谱宽度较小时,转换效率随光谱宽度的增加而缓慢降低;当光谱宽度大于18 nm时,转换效率急剧下降。每种荧光粉都有其理想激发源光谱宽度范围,在此范围内激发源辐射通量转换效率高且受其光谱宽度影响较弱。     

Singlet-Singlet Electronic Excitation Energy Transfer in a Bichromophore Cooled in a Supersonic Jet

The fluorescence excitation spectra and polarization of the fluorescence of a bichromophore cooled in a supersonic jet are measured. The bichromophore consists of 2,5-diphenyloxazole (PPO) and 1-(5′-phenyl-1′, 3′-oxazole-2′-yl)-4-(5′-phenyl-1′,3′,4′-oxadiazole-2′-yl)-benzene (POPDP) connected by the methylene bridge -(CH₂)-. Based on the analysis of these components and theoretical calculations, it has been proven that the total intramolecular singlet-singlet transfer of the energy of electronic excitation from the energy donor PPO to the acceptor POPDP occurs in a time of 10⁻¹² sec. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 4, pp. 460–463, July–August, 2005.     

核破裂中的激发能的作用

在晶格气体模型的框架中研究了¹²⁹Xe系统在破裂过程中的热力学性质和轻粒子发射性质随核温度和系统的冻结密度的变化规律.计算发现在不同的冻结密度下,¹²⁹Xe破裂过程的物理观测量呈现了不同的温度相关性.在这种情况下,核物质液气相变发生时的临界温度强烈地依赖于系统的冻结密度.当激发能代替温度作为一个自变量时,临界激发能将不再灵敏地依赖于系统的冻结密度.除此之外,由于不同冻结密度而引起的不同粒子发射产额的温度相关性,也随着激发能的应用,出现了几乎一致的激发能依赖性.从这些结果中可以认为,激发能可以作为一个控制核破裂的基本物理量和标度量.     

强耦合表面极化子的激发能量

采用线性组合算符方法及幺正变换方法研究了电子与表面光学(SO)声子和体纵光学(LO)声子均为强耦合的表面极化子的激发态性质.计算了体系的有效哈密顿量、振动频率和体系由基态向第一激发态跃迁所需的激发能量.     

Search for Higgs Boson in UHE Cosmic Rays

Considering the SM Higgs boson mass in the range of (95–235) GeV, we present here a mechanism for indirect searches of this scalar in UHE cosmic rays interactions. The mechanism is the decay of Higgs bosons which are produced through bubble formation due to vacuum excitation in an UHE cosmic rays interactions with air nuclei. We develop a model of hadronic interaction based on algorithms of the GENCL code of the UA5 experiment of CERN and some physics of CORSIKA code (Karlsruhe report), incorporating a fraction of energy transfer to bubble formation through vacuum excitation and subsequent multiparticle production via conversion of Higgs boson to heavy fermion pairs. Such events are expected to have high multiplicity and excess muons. This mechanism has significant effect starting from E _P 10¹⁸eV. It is found that the average muon number decreases gradually upto 175 GeV Higgs boson mass and remain practically constant thereafter for all primary energies (E _P) above 10¹⁸ eV and for all fractions of energy transfer (f _e 0.01–0.5). The fluctuation of muon multiplicity decreases with E _P and increases very slowly with Higgs mass upto 175 GeV, remaining practically invariant thereafter.     

基于全息成像技术构建任意的二维光晶格阵列

利用Gerchberg-Saxton算法生成任意的二维光晶格阵列的全息图,并且将全息图加载到液晶型空间光调制器上,然后将850 nm的激光照射到空间光调制器的液晶屏上,利用透镜的傅里叶变换特性,成功地显示或构建任意形状的二维光晶格阵列。将该系统应用到87Rb的冷原子实验中,成功俘获冷原子,这为接下来的单原子多量子位的量子模拟实验奠定了基础。     

Nuclear Level Density at High Spin and Excitation Energy

The intensive studies of equilibrium processes in heavy-ion reaction have produced a need for information on nuclear level densities at high energies and spins. The Fermi gas level density is often used in investigation of heavy-ion reaction studies. Some papers have claimed that nuclear level densities might deviate substantially from the Fermi gas predications at excitations related to heavy-ion reactions. The formulae of calculation of the nuclear level density based on the theory of superconductivity are presented, special attention is paid to the dependence of the level density on the angular momentum. The spin-dependent nuclear level density is evaluated using the pairing interaction. The resulting level density for an average spin of 52 ħ is evaluated for ¹⁵⁵Er and compared with experimental data. Excellent agreement between experiment and theory is obtained.     

Spectral Sensitization of the Photosensitivity of a Molecular Medium by Electronic Excitation Energy Acceptors

The possibility of using photolytically active acceptors of the electronic excitation energy to expand the spectral sensitivity region and to perform optical recording with amplification in molecular media is considered. An analysis of image formation under energy transfer conditions described by the Perrin model is made. The possibilities of increasing the sensitivity and contrast of recording are revealed.