Tigran V. Shahbazyan

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We study the role of spin correlations in nonlinear absorption due to transitions from a deep impurity level to states above a Fermi sea. We demonstrate that the Hubbard repulsion between two electrons at the impurity leads to a logarithmic divergence in chi(3) at the absorption threshold. This divergence is a manifestation of the Kondo physics in the(More)
We identify a new mechanism for cooperative emission of light by an ensemble of N dipoles near a metal nanostructure supporting a surface plasmon. The cross talk between emitters due to the virtual plasmon exchange leads to the formation of three plasmonic superradiant modes whose radiative decay rates scale with N, while the total radiated energy is thrice(More)
Using time-resolved pump-probe spectroscopy, we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The(More)
Metal photoluminescence (MPL) originates from radiative recombination of photoexcited core holes and conduction band electrons. In metal nanostructures, MPL is enhanced due to the surface plasmon local field effect. We identify another essential process in plasmon-assisted MPL-excitation of Auger plasmons by core holes-that hinders MPL from small(More)
We develop a microscopic model for fluorescence of a molecule (or semiconductor quantum dot) near a small metal nanoparticle. When a molecule is situated close to metal surface, its fluorescence is quenched due to energy transfer to the metal. We perform quantum-mechanical calculations of energy transfer rates for nanometer-sized Au nanoparticles and find(More)
We study the role of collective surface excitations in the electron relaxation in small metal particles. We show that the dynamically screened electron– electron interaction in a nanoparticle contains a size–dependent correction induced by the surface. This leads to new channels of quasiparticle scattering accompanied by the emission of surface collective(More)
By means of degenerate four-wave mixing (FWM), we investigate the quantum coherence of electron-hole pairs in the presence of a two-dimensional electron gas in modulation–doped GaAs-AlGaAs quantum wells in the quantum Hall effect regime. With increasing magnetic field, we observe a crossover from Markovian to non–Markovian behavior, as well as large jumps(More)
We develop a non–equilibrium many–body theory of the coherent femtosecond 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 with(More)