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condensation (BEC) in a binary mixture of Bose gases.The effective potential, which preserves the Goldstonetheorem, is found in the Hartree-Fock (HF)approximation. This quantity is then used to considerthe equation of state (EOS) and the phase transition ofthe system.Người trình bày: Lê Viết Hòa30. Electronic band structure of GrapheneSuperlatticesPhạm Công Huy, Nguyễn Hải ChâuElectronic band structure of graphene superlattices witha Kronig-Penney-like potential has been in detailsanalyzed. Using the T-matrix approach, we derived theexpression of energy as a function of the wavevector andstudied the dependence of the miniband structure on theother parameters. The anisotropic behaviors of masslessDirac fermions are investigated. The group velocity isanisotropically renormalized, while it is unchanged atall for states with wavevector in one direction but isreduced to zero in another. This implies several usefulapplications in nanoscale electronic devides. We alsoshowed that new Dirac points are generated anddemonstrated that the number of them is controlled bythe strength and period of potential which has dramaticconsequences on electronic properties of system.Người trình bày: Phạm Công Huy31. Electroluminescence from intersubband cavitypolariton states in the mid-infrared domain.Thành phố Đồng Hới (03- 06/8/2009) Trang 39/ 102PiereJouytrong coupling appears when photons are confined withan electronic transition of the same energy. In this regime,the energy diagram is strongly modified and replaced bypolariton states dispersion. We recently demonstratedElectric-field tunable electroluminescence fromintersubband transitions in a quantum well via the strongcoupling of the electronic transitions with an opticalcavity mode in the mid-infrared domain. The deviceconsists of a quantum cascade structure embedded in aplanar metal-dielectric microcavity where electrons can beresonantly injected at different energies, thanks to thepolariton dispersion curve. The electroluminescencetuning shows a strong far field angular dependence inaccordance with the conservation of the in-planemomentum. Our experiment illustrates that it is possibleto connect quantum optics and electronic transport insemiconductor heterostructuresNgười trình bày: Piere Jouy32. Improved light trapping in silicon nanowiresolar cellsBenedict O’ DonnellConcerns over the sustainability of our current methodsfor generating electricity are spurring the development ofphotovoltaic solar energy conversion. Most solar panelssold today are made from high purity crystalline silicon,making them expensive compared to conventional energysources. Over the past thirty years, research on thin-filmshas brought a new generation of photovoltaic cells, madeThành phố Đồng Hới (03- 06/8/2009) Trang 40/ 102