Biomedical subjects

T V Shahbazyan

Publications and source records attributed to T V Shahbazyan.

4 recordsLinked to original sources

PubMed2007

Coherent acoustic vibration of metal nanoshells.

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 modulation amplitude is significantly stronger, and the period is longer than that in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.

Acoustics↗

PubMed2006

Two-electron linear intersubband light absorption in a biased quantum well.

We point out a novel manifestation of many-body correlations in the linear optical response of electrons confined in a quantum well. Namely, we demonstrate that along with the conventional absorption peak at a frequency omega close to the intersubband energy delta, there exists an additional peak at frequency h omega approximately = 2delta. This new peak is solely due to electron-electron interactions, and can be understood as excitation of two electrons by a single photon. The actual peak line shape is comprised of a sharp feature, due to excitation of pairs of intersubband plasmons, on top of a broader band due to absorption by two single-particle excitations. The two-plasmon contribution allows us to infer intersubband plasmon dispersion from linear absorption experiments.

Journal Article↗

PubMed2000

Spin correlations in nonlinear optical response: light-induced Kondo effect.

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 nonlinear optical response of Fermi sea systems. We also show that, for off-resonant pump excitation, the pump-probe spectrum exhibits a narrow peak below the linear absorption onset. Remarkably, the light-induced Kondo temperature, which governs the shape of the Kondo-absorption spectrum, can be tuned by varying the intensity and frequency of the pump.

Journal Article↗

PubMed2000

Femtosecond coherent dynamics of the fermi-edge singularity and exciton hybrid.

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 that, for off-resonant pump excitation, the pump-probe spectrum undergoes a striking transformation, with a time-dependent exchange of oscillator strength between the Fermi-edge singularity and exciton peaks. This effect originates from the many-body electron-hole correlations which determine the dynamical response of the Fermi sea.

Journal Article↗