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Search Results: 1 - 10 of 126583 matches for " Zhibing Li "
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Transient of the kinetic spherical model between two temperatures
Chunshan He,Zhibing Li
Physics , 2003,
Abstract: We solve the dynamic equation for the kinetic spherical model that initially is in an arbitrary equilibrium state and then is left to evolve in a heat-bath with another temperature. Flows of the Renormalizational group are determined.
Graphene with the secondary amine-terminated zigzag edge as a line electron emitter
Weiliang Wang,Zhibing Li
Physics , 2012, DOI: 10.1007/s00339-012-7180-3
Abstract: An extraordinary low vacuum barrier height of 2.30 eV has been found on the zigzag-edge of graphene terminated with the secondary amine via the ab initio calculation. This edge structure has a flat band of edge states attached to the gamma point where the transversal kinetic energy is vanishing. We show that the field electron emission is dominated by the flat band. The edge states pin the Fermi level to a constant, leading to an extremely narrow emission energy width. The graphene with such edge is a promising line field electron emitter that can produce highly coherent emission current.
Comment on slope of nonlinear FN plot and field enhancement factor
Weiliang Wang,Zhibing Li
Physics , 2012,
Abstract: It is common practice to extract field enhancement factor from the slope of FN plot. Many experimentalists working on field electron emission had reported multi-(linear segment) FN plots, which can be divided into several (usually two) linear segments. Then multi-(field enhancement factor) were extracted from the FN plot. They claimed that the field enhancement factor increases with applied field if the FN plot bends downward (vice versus if the FN plot bends upward). We show that this is contrary to fact.
Characteristic frequency of the magnetic radiation of spinor condensates
Zhibing Li,Chengguang Bao
Physics , 2007, DOI: 10.1103/PhysRevA.75.063606
Abstract: The magnetic radiation of the fully-condensed states of $^{23}$Na condensates have been studied. A narrow characteristic spectral line with a wave length proportional to N^(-2/5) (N is the number of particles) and with a probability of transition proportional to N^(17/5) emitted (absorbed) by the condensate was found. It implies that short wave radiation with a huge probability of transition can be obtained if numerous atoms are trapped. A new technique developed by the authors, namely, the analytical forms of the fractional parentage coefficients, was used to calculate analytically the matrix elements between the total spin-states.
Explanation of the Stern-Gerlach splitting of spinor condensates based on symmetry
Zhibing Li,Chengguang Bao
Physics , 2007,
Abstract: The Stern-Gerlach splitting of spinor condensates is explained based on the total spin-states with specified SU(2) and permutation symmetries.
Potential barrier of Graphene edges
Weiliang Wang,Zhibing Li
Physics , 2011, DOI: 10.1063/1.3587186
Abstract: We calculated row resolved density of states, charge distribution and work function of graphene's zigzag and armchair edge (either clean or terminated alternatively with H, O or OH group). The zigzag edge saturated via OH group has the lowest work function of 3.76 eV, while the zigzag edge terminated via O has the highest work function of 7.74 eV. The angle-dependent potential barrier on the edge is fitted to a multi-pole model and is explained by the charge distribution.
Analytic solution of charge density of single wall carbon nanotube in conditions of field electron emission
Zhibing Li,Weiliang Wang
Physics , 2006, DOI: 10.1088/0256-307X/23/6/072
Abstract: We derived the analytic solution of induced electrostatic potential along single wall carbon nanotubes. Under the hypothesis of constant density of states in the charge-neutral level, we are able to obtain the linear density of excess charge in an external field parallel to the tube axis.
Simulation for field emission images of micrometer-long SWCNTs
Weiliang Wang,Ningsheng Xu,Zhibing Li
Physics , 2009, DOI: 10.1016/j.ultramic.2009.05.013
Abstract: The electron distribution of open-ended single-walled carbon nanotubes with chirality indexes (7,0) and (5,5) in the field emission conditions was calculated via a multi-scaled algorithm. The field emission images were produced numerically. It was found that the emission patterns change with the applied macroscopic field. Especially, the symmetry of the emission pattern of the (7,0) carbon nanotube is breaking in the lower field but the breaking is less obvious in the higher field. The enlargement factor increases with the applied macroscopic field.
Spin evolution of spin-1 Bose-Einstein condensates
Ma Luo,Zhibing Li,Chengguang Bao
Physics , 2007, DOI: 10.1103/PhysRevA.77.043625
Abstract: An analytical formula is obtained to describe the evolution of the average populations of spin components of spin-1 atomic gases. The formula is derived from the exact time-dependent solution of the Hamiltonian $H_{S}=c mathbf{S}^{2}$ without using approximation. Therefore it goes beyond the mean field theory and provides a general, accurate, and complete description for the whole process of non-dissipative evolution starting from various initial states. The numerical results directly given by the formula coincide qualitatively well with existing experimental data, and also with other theoretical results from solving dynamic differential equations. For some special cases of initial state, instead of undergoing strong oscillation as found previously, the evolution is found to go on very steadily in a very long duration.
Rotation Symmetry Spontaneous Breaking of Edge States in Zigzag Carbon Nanotubes
Weiliang Wang,Ningsheng Xu,Zhibing Li
Physics , 2008, DOI: 10.1021/jp9044868
Abstract: Analytical solutions of the edge states were obtained for the (N, 0) type carbon nanotubes with distorted ending bonds. It was found that the edge states are mixed via the distortion. The total energies for N=5 and N>=7 are lower in the asymmetric configurations of ending bonds than those having axial rotation symmetry. Thereby the symmetry is breaking spontaneously. The results imply that the symmetry of electronic states at the apex depends on the occupation; the electron density pattern at the apex could change dramatically and could be controlled by applying an external field.
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