[en] We investigate the localization of surface exciton-polaritons in the presence of random roughness and spatial dispersion. The localization criteria are examined. The localization effects are embodied in the large enhancement and rapid decay of the field intensity on the surface. The calculation shows that the localization occurs in a limited frequency range above the resonant frequency of transverse excitons

[en] The Hartree–Fock–Popov theory of interacting Bose particles is generalized to the Cooper-pair system with a screened Coulomb repulsive interaction in high-temperature superconductors. At zero temperature, we find that the condensate density n_c(0) of Cooper pairs and the phonon velocity c(0) are dome-shaped functions of the p hole concentration δ. At finite temperature T, we find that the condensate fraction n_c(T)/n and the phonon velocity c(T) decrease continuously from n_c(0)/n or c(0) to zero as T increases from zero to the transition temperature T_c. The Cooper-pair system undergoes a first-order phase transition from the normal state to the Bose condensed state.

[en] We establish the photonic superfluid theory in waveguides made of self-defocussing polar crystals. In quantum theory it is shown that photons can sense an attractive effective interaction by exchange of virtual optical phonons. Such an interaction leads to the photonic superfluid state, in which a propagating photon pair consists of a combination of two photons with opposite transverse wave vector and spins. The most important property of the photonic superfluid state is that the system of photon pairs evolves without scattering attenuations. The traveling-wave superfluid state has the squeezing property and the soliton effect.

[en] As a model of the cuprate superconductors, we have studied the p hole motion in a planar antiferromagnetic (AFM) background and a c-axis boson field. The indirect coupling between the d spins through the p holes is considered. In a range of the hole concentration, the indirect Cu-Cu interaction enhances the planar AFM coupling though it destroys the weak c-axis AFM order. At higher concentrations, the compensation of the d spins by the p holes occurs. For the the strong p-d exchange coupling, the p holes can pair to form small magnetic bipolarons in the enhanced planar AFM background. The in-plane motion of the bipolarons is independent of the c-axis motion assisted by bosons. The superconducting properties of the cuprate superconductors are determined by a 2+1 dimensional bipolaron Hamiltonian. The results obtained from our model are consistent with the observations on the cuprate superconductors. (orig.)

[en] We find that uniform Bose atomic gases with weak attraction can undergo a Bardeen-Cooper-Schrieffer (BCS) condensation below a critical temperature. In the BCS condensation state, bare atoms with opposite wave vectors are bound into pairs, and unpaired bare atoms are transformed into a new kind of quasi-particles, i.e. the dressed atoms. The atom-pair system is a condensate or a superfluid and the dressed-atom system is a normal fluid. The critical temperature and the effective mass of dressed atoms are derived analytically. The transition from the BCS condensation state to the normal state is a first-order phase transition. (author)

[en] In a Kerr nonlinear blackbody, bare photons with opposite wave vectors and helicities are bound into pairs and unpaired photons are transformed into a different kind of quasiparticle, the nonpolariton. The nonpolariton system constitutes free thermal radiation in the blackbody. The present paper investigates the radiation properties of a Kerr nonlinear blackbody. We found that the spectral energy density and radiation pressure of a Kerr nonlinear blackbody are larger than those of a normal blackbody and that these two quantities are monotonically decreasing functions of the Kerr nonlinear coefficient. Above the transition temperature the photon system is in a normal thermal radiation state, but below the transition temperature it is in a squeezed thermal radiation state. In the transition from the normal to the squeezed thermal radiation state, the phase symmetry of the photon system is spontaneously broken

[en] Highlights: • A LFR which employs CPC, evacuated tubes and uses molten salt as HTF is designed. • 3D optical and thermal models are developed with MCRT and FVM methods. • The optical and thermal performance, the effects of key parameters are studied. • The instantaneous optical efficiency of 65.0% is achieved at normal incidence. • The collector efficiencies are above 46.0% under all the studied conditions. - Abstract: A novel linear Fresnel reflector which employs the evacuated tube, CPC secondary reflector, and uses molten salt as the heat transfer fluid (HTF) was designed and studied in this paper. A 3D optical model was developed to simulate the radiation transmission within the system with Monte Carlo Ray Tracing (MCRT) method. Based on the model, firstly, the optical performance of the systems using cylindrical and parabolic mirrors was compared. Then the local solar flux distribution on the absorber surface and the optical efficiency were computed. Then the effects of the slope error, time and location, etc. were investigated. Finally, the thermal performance was investigated by coupling the MCRT with the Finite Volume Method (FVM). The optical simulation results indicate that the system with optimized cylindrical mirrors can achieve nearly the same performance as the one with parabolic mirrors. The solar flux distribution on the absorber exhibits a non-uniform characteristic which can be improved by using mirrors with proper slope error. The instantaneous optical efficiency of 65.0% at normal incidence and the annual mean optical efficiency which ranges between 55.2% and 34.8% from the equator to N50° can be achieved. The numerical results indicate that the temperature profiles on the absorber follow the non-uniform solar flux. The collector efficiencies are all above 46.0% under the studied conditions. Both the thermal efficiency and the collector efficiency increase with decreasing salt temperature and with increasing radiation. These results suggest that the introduced system is a feasible choice for using molten salt as the HTF in Fresnel system

[en] We develop a numerical model to investigate the localization of surface exciton polaritons in the presence of random roughness and spatial dispersion. The localization criteria are examined. The localization effects are embodied in the large enhancement and rapid decay of the field intensity on the surface. The calculation shows that there is a transition from the localized state to the extended state. It has been found that the localization occurs in a limited frequency range above the resonant frequency of transverse excitons

[en] We study squeezed properties of magnon squeezed thermal spin states by using the distribution of Q function in the ferromagnet. It is found that the distribution of Q function strongly depends on the temperature T and coupling parameter γ. Below the transition temperature T_c, the distribution Q function in the squeezed thermal spin state presents a richer structure than in the normal state. Non-classical effects have been observed. In the transition from the normal to the squeezed thermal spin state, the phase symmetry of the magnon system is spontaneously broken.

[en] We investigate the decay rate of an atom in a two-dimensional optical microcavity in which there exists a Bose-Einstein condensation of photons. It is found that below the critical temperature Tc, the atomic decay rate depends on the absolute temperature T. Especially, at absolute zero temperature almost all photons are in the condensate state, and the atom can be approximately treated as if it is in vacuum. (authors)