| 1. |
- Kaputkina, N.E., et al.
(författare)
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Influence of the magentic field on formation and spectrum of the exciton-polariton in a microcavity
- 2006
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Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 378-380, s. 1049-1050
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic field effect on properties of exciton–polaritons in an optical microcavity and on direct and indirect excitons in single and coupled quantum wells is considered. Magnetic field controls exciton dispersion curve and its intersection with microcavity photon dispersion curve. This gives the possibility to control exciton–polariton formation, polariton splitting and polariton dispersion. Excitons and exciton–polaritons on higher Landau levels are discussed.
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| 2. |
- Lozovik, Yu. E., et al.
(författare)
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Bose condensation of two-dimensional dipolar excitons : Simulation by the quantum Monte Carlo method
- 2008
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 106:2, s. 296-315
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Forskningsöversikt (refereegranskat)abstract
- The Bose condensation of two-dimensional dipolar excitons in quantum wells is numerically studied by the diffusion Monte Carlo simulation method. The correlation, microscopic, thermodynamic, and spectral characteristics are calculated. It is shown that, in structures of coupled quantum wells, in which low-temperature features of exciton luminescence have presently been observed, dipolar excitons form a strongly correlated system.
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| 3. |
- Lozovik, Yu E, et al.
(författare)
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Crystallization and quantum melting of few electron system in a spherical quantum dot : quantum Monte Carlo simulation
- 2003
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Ingår i: Solid State Communications. - : Elsevier Science B.V., Amsterdam.. - 0038-1098 .- 1879-2766. ; 125:2, s. 127-131
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Tidskriftsartikel (refereegranskat)abstract
- Spherical quantum dots with a few charged Fermi particles (electrons or holes) are studied for different total spins. Simulation by quantum path integral Monte Carlo method is performed. The dependence of the electron correlations in the quantum dot is studied at different mean interelectron separation controlled by number of electrons in the quantum dot and by steepness of electron confinement (the latter parameter can be changed by the gate voltage). The cold melting-quantum transition from Wigner crystal-like state (i.e. from regime of strongly correlated electrons) to a Ferad liquid-like state-driven by the steepness of electron confinement is studied. The pair correlation function and radial function characterizing electron quantum delocalization are analyzed.
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| 4. |
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| 5. |
- Lozovik, Yu E, et al.
(författare)
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Structural properties of the condensate in two-dimensional mesoscopic systems of strongly correlated excitons
- 2004
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Ingår i: JETP Letters. - : Springer Science Business Media. - 0021-3640 .- 1090-6487. ; 79:10, s. 473-478
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional mesoscopic Bose system of dipoles in a 2D trap is considered using computer simulation by the quantum path-integral Monte Carlo method. The model describes a rarefied system of spatially indirect excitons in a confining potential. Bose condensation in the system and its superfluid and structural properties are studied over a wide range of interparticle spatial correlations, from an almost ideal Bose gas to the regime of a strongly correlated system. It is found that, at strong interparticle spatial correlations, particles in the condensate form a crystal-like structure. In this case, the spatial correlations of particles in the condensate are less pronounced than the correlations of noncondensed particles. The effect of recurrent crystallization is observed in the regime of strong interparticle correlations.
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| 6. |
- Aiboushev, A. V., et al.
(författare)
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Enhanced luminescence and two-photon absorption of silver nano-clusters
- 2009
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Ingår i: Physica Status Solidi c. - : Wiley. - 1862-6351 .- 1610-1642. ; 6:0, s. S162-S166
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Tidskriftsartikel (refereegranskat)abstract
- Luminescence of silver nanoparticles photo-deposited on titan dioxide nanoparticles of mesoporous film is studied. Luminescence was registered under the two-photon excitation by femto-second laser pulses of Ti:sapphire laser. It was observed that Ag/ TiO2 mesoporous films have high concentration of bright luminescence spots which reveal stability to degradation under long illumination. Various configurations of silver nanoparticles are analyzed to explain the physics of bright luminescence spots ( hot spots). Luminescence intensity reveals hot spots dependence on the polarization of excitation laser pulse. Properties of Ag/TiO2 system can be useful for single molecule spectroscopy and visualization of biological objects. Aapplication of Ag/ TiO2 mesoporous films for Raman scattering spectroscopy de-menstruated for the case of Rhodamine B.
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| 7. |
- Bogdanova, M.V., et al.
(författare)
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Absorption spectra versus field distribution for metal-dielectric three-dimensional photonic crystals
- 2008
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Ingår i: Laser physics. - : Pleiades Publishing Ltd. - 1054-660X .- 1555-6611. ; 18:4, s. 417-423
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Tidskriftsartikel (refereegranskat)abstract
- The absorption spectra of three-dimensional metal-dielectric photonic crystals (PCs) are studied using computer simulation by the finite difference time domain method and the layered Korringa-Kohn-Rostoker method. The band structure of a three-dimensional dielectric PC is obtained by the plane wave expansion method. The explanation of absorption spectra of PC based on its comparison with the band structure and Fabry-Perot resonances inside a PC plate is given. The intensity distribution of an electric field using FDTD inside the metal-dielectric PC for three various structures is analyzed. It is shown that spherical cavities in a dielectric PC "focus" the field inside cavities at certain wavelengths. This leads to an increase of absorption at these wavelengths if metal spheres are located in the centers of those cavities. This effect can be considered as an analogue of the Borrmann effect in X-ray spectroscopy. © 2008 MAIK Nauka.
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| 8. |
- Lozovik, Yu E, et al.
(författare)
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Coherent phases and magnetoexcitons in graphene
- 2009
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Ingår i: PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE. - : Wiley. - 1862-6300. ; 206:5, s. 927-930
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Tidskriftsartikel (refereegranskat)abstract
- Unique band structure peculiarities of graphene imply that near Fermi level electrons are described by two-dimensional Dirac equation for massless particles. We investigate how these peculiarities manifest in electron-hole pairing and properties of indirect magnetoexcitons in two spatially separated, independently gated graphene layers. For electron-hole pairing, we derive asymptotical expressions for the gap in energy spectrum and discuss system behavior at various controlling parameters. We derive dispersion relations for magnetoexcitons and their effective-mass decompositions, and also discuss a possibility of magnetoexcitonic super-fluidity. The systems under consideration can reveal coherent properties, dissipationless currents and Josephson phenomena at room temperature.
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| 9. |
- Lozovik, Yu. E., et al.
(författare)
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Superfluidity of two-dimensional excitons in flat and harmonic trapsI. L.
- 2007
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Ingår i: Physics Letters A. - : Elsevier BV. - 0375-9601 .- 1873-2429. ; 366:4-5, s. 487-492
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Tidskriftsartikel (refereegranskat)abstract
- Superfluid exciton density and superfluid transition (crossover) temperature are calculated for 2D excitons in large-size flat and harmonic traps. A generalized local density approximation for the Kosterlitz–Thouless theory is developed
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| 10. |
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| 11. |
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| 12. |
- Willander, Magnus, 1948, et al.
(författare)
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Fundamentals and properties of zinc oxide nanostructures: optical and sensing applications
- 2008
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Ingår i: Superlattices and Microstructures. - : Elsevier BV. - 0749-6036 .- 1096-3677. ; 43:4, s. 352-61
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we will give an overview of the status of catalytic growth and of low-temperature chemical growth of ZnO nanostructures performed in our laboratory. Particularly results employing different substrates will be discussed. The second part deals with structural and optical properties of ZnO nanorods. The results from high resolution transmission electron microscope (HRTEM), scanning electron microscope (SEM), photoluminescence (PL), Cathodoluminescence (CL), and Electroluminescence (EL), on single nanowires will be shown. Our results on surface morphology, bulk and the position of the catalyst as well as the optical properties including UV emission, lasing and white emission will all be presented and discussed. In the third part experimental results from electroluminescence of ZnO nanorods on different substrates in the UV in addition to excellent white light emission obtained from samples grown at low temperature are to be given and discussed. Finally the sensing of molecules in water by ZnO nanorods will be discussed from a theoretical point of view. Also fundamental properties of polaritons and excitons in ZnO nanostructures are to be highlighted.
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| 13. |
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| 14. |
- Willander, Magnus, 1948, et al.
(författare)
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Solid and soft nanostructured materials: fundamentals and applications
- 2005
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Ingår i: Microelectronics Journal. - : Elsevier BV. - 0026-2692. ; 36:11, s. 940-949
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Tidskriftsartikel (refereegranskat)abstract
- The scientific work worldwide on nanostructured materials is extensive as well as the work on the applications of nanostructured materials. We will review quasi two-, one- and zero-dimensional solid and soft materials and their applications. We will restrict ourselves to a few examples from partly fundamental aspects and partly from application aspects. We will start with trapping of excitons in semiconductor nanostructures. The subjects are: physical realizations, phase diagrams, traps, local density approximations, and mesoscopic condensates. From these fundamental questions in solid nanomaterials we will move to trapping of molecules in water using nanostructured electrodes. We will also discuss how to manipulate water (create vortices) by nanostructure materials. The second part deals with nanorods (nano-wires). Particularly we will exemplify with ZnO nanorods. The reason for this is that ZnO has: a very strong excitons binding energy (60 meV) and strong photon–excitons coupling energy, a strong tendency to create nanostructures, and properties which make the material of interest for both optoelectronics and for medical applications. We start with the growth of crystalline ZnO nanorods on different substrates, both crystalline (silicon, silicon carbide, sapphire, etc) and amorphous substrates (silicon dioxide, plastic materials, etc) for temperatures from 50 °C up to 900 °C. The optical properties and crystalline properties of the nanorods will be analyzed. Applications from optoelectronics (lasers, LEDs, lamps, and detectors) are analyzed and also medical applications like photodynamic cancer therapy are taken up. The third part deals with nano-particles in ZnO for sun screening. Skin cancer due to the exposure from the sun can be prevented by ZnO particles in a paste put on the exposed skin.
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