Tigran V. Shahbazyan

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We study finite-size effects in surface-enhanced Raman scattering (SERS) from molecules adsorbed on small metal particles. Within an electromagnetic description of SERS, the enhancement of the Raman signal originates from the local field of the surface plasmon resonance in a nanoparticle. With decreasing particle sizes, this enhancement is reduced due to(More)
We develop a theory describing the effects of many–particle Coulomb correlations on the coherent ultrafast nonlinear optical response of semiconductors and metals. Our approach is based on a mapping of the nonlinear optical response of the " bare " system onto the linear response of a " dressed " system. The latter is characterized by effective(More)
We study the energy spectrum of a system of localized states coupled to a 2D electron gas in strong magnetic field. If the energy levels of localized states are close to the electron energy in the plane, the system exhibits a kind of collective behavior analogous to the Dicke effect in optics. The latter manifests itself in " trapping " of electronic states(More)
A new theoretical approach for the calculation of optical properties of complex solutions is proposed. It is based on a dielectric matrix εm with included small metallic inclusions (less than 3 nm) of spherical shape. We take into account the mutual interactions between the inclusions and the quantum finite-size effects. On the basis of the effective medium(More)
We study theoretically the coherent nonlinear optical response of doped quantum wells with several subbands. When the Fermi energy approaches the exciton level of an upper subband, the absorption spectrum acquires a characteristic double-peak shape originating from the interference between the Fermi-edge singularity and the exciton resonance. We demonstrate(More)
We study theoretically the ultrafast nonlinear optical response of quantum well excitons in a perpendicular magnetic field. We show that for magnetoex-citons confined to the lowest Landau levels, the third-order four-wave-mixing (FWM) polarization is dominated by the exciton-exciton interaction effects. For repulsive interactions, we identify two regimes in(More)
We develop a non–equilibrium many–body theory of the coherent femtosec-ond nonlinear optical response of the Fermi edge singularity. We study the role of the dynamical Fermi sea response in the time–evolution of the pump–probe spectra. The electron–hole correlations are treated nonperturbatively with the time–dependent coupled cluster cxpansion combined(More)
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