Chang-de Gong

Squeezing of the kth power of the field amplitude

Abstract k th power amplitude squeezing (KPAS) is strictly hown to be a nonclassical effect ( k >2). It can appear in a Kerr medium. For two states, the relations between KPAS the and common squeezing, Hong-Mandel squeezing and antibuching are investigated. The results show that the former is another new nonclassical effect inequivalent to the latter three.

Transfer matrix method for a semi-infinite layered electron gas

Abstract A transfer matrix method is given for the electronic collective modes of a semi-infinite layered electron gas system with different dielectric media on either side of the surface. Analytic formulas are derived for the induced potential along the superlattice direction, analysis shows that there are no Van Hove singularities in the allowed spectrum.

Structures of inert atomic clusters and their magic numbers of geometry

Abstract The optimal configurations of all atoms in atomic microclusters of an inert element have been obtained from their arbitrary positions and shapes by means of a Lennard-Jones interaction potential between atoms in the clusters, calculating the binding energies of the clusters with the numbers of atoms N ⩽ 14, which have shown the magic numbers of geometry in accordance with the experimental results. The structural pictures of such clusters are also presented.

A single parameter scaling theory in a disordered layered system

We show that in a disordered layered system all states are localized if kFl<4Πgc, irrespective of the interlayer coupling t ⊥. The crossover of dimensionality depends on t⊥. Near the critical value t⊥c at which the Anderson transition occurs, the correlation length ζm and the localization length ζloc are calculated.

Dynamics of a single hole in a quantum antiferromagnet: self-consistent Born approximation study

Abstract We present a representation where holes are described as spinless fermions and the spin system as interacting bosons undergoing Bose-Einstein condensation to study the dynamics of a single hole in a two-dimensional quantum antiferromagnet within the self-consistent Born approximation. The advantage of this approach is that one can uniformly handle the t-J model and the t-t′-J model.

Modified spin-wave theory of doped antiferromagnet on a square lattice

Abstract We apply the modified spin-wave theory for the effective Hamiltonian which describes a two-dimensional doped antiferromagnet. A critical hole concentration δ c is obtained. The low-temperature dependence of the antiferromagnetic correlation length is quite different in the δ δ c , δ = δ c and δ>δ c regimes, which is qualitatively in agreement with the results of neutron scattering experiments.

The Peierls instability and superconductivity in quasi-2-d La2-x(Ba,Sr)xCuO4 compounds

Abstract The Peierls instability in the quasi-2-d La 2- x (Ba,Sr) x CuO 4 is reexamined by taking the weak interlayer coupling into account. A two-step Peierls transition theory is developed, the general misunderstandings on the Peierls instability are therefore clarified, and a number of experimental anomalies observed in La 2 CuO 4 are well explained. By suggesting an additional change of space group symmetries at the lower transition point, the calculated band structures are also intepreted. The possibility of CDW coexistence with the high- T c superconductivity, the possible evidence for the 3-d superconductivity of the high- T c materials are discussed with this theory.

A new mechanism of high Tc superconductivity

Abstract On the assumption that doping creates holes on the O rather than the Cu sites, a new model to describe the CuO 2 planes in the high T c superconductor is proposed. It is shown that the RVB state of the holes on Cu sites at half-filling will lead to an effective attraction of the holes on the O sites which is responsible for superconductivity. Specific heat and susceptibility are discussed briefly and are consistent with experimental results.

Qualitative study of the boundary correlation function in the two-dimensional XY-model

Abstract The two-point correlation function at the rectilinear boundary of the two-dimensional half-space is studied for the XY-model for the case of free boundary conditions. It is shown that defects of vortex-type at the boundary form a one-dimensional plasma for T ≠ 0, but that this does not lead to exponential decay of the boundary correlation function for T

Tunable striped-patterns by lattice anisotropy and magnetic impurities in d-wave superconductors

The pattern transition induced by lattice anisotropy (LA) and magnetic impurities is computationally observed in near-optimally doped d-wave superconductors (DSCs). For the single impurity case, a transition from the checkerboard to stripe pattern can be induced by a very weak LA. For the two-impurity case, an orientation transition from the longitudinal stripe into transverse pattern is observed when the LA ratio reaches some critical value. At the critical point, the structures around impurities can restore checkerboard patterns. These results indicate that the formation of stripes in DSCs might induced by various effects, and could be tunable experimentally.