We show that optical two-dimensional (2D) spectroscopy can recover ultrafast heterogeneous dynamics of closely spaced delocalized exciton states from a molecular exciton manifold characterized by a single absorption band. The complete experimental third-order nonlinear optical response from room-temperature J-aggregates in liquid phase is reproduced for the first time with self-consistent Frenk...

The hydrodynamic equations for indirect excitons in the double quantumwells are studied taking into account 1) a possibility of an exciton condensed phase formation, 2) the presence of pumping, 3) finite value of the exciton lifetime, 4) exciton scattering by defects. The threshold pumping emergence of the periodical exciton density distribution is found. The role of localized and free exciton ...

We report on original nonlinear spectral hole-burning experiments in single wall carbon nanotubes that bring evidence of pure dephasing induced by exciton-exciton scattering. We show that the collision-induced broadening in carbon nanotubes is controlled by exciton-exciton scattering as for Wannier excitons in inorganic semiconductors, while the population relaxation is driven by exciton-excito...

We propose a physical mechanism which enables permanent Rabi oscillations in driven-dissipative condensates of exciton-polaritons in semiconductor microcavities subjected to external magnetic fields. The method is based on stimulated scattering of excitons from the incoherent reservoir. We demonstrate that permanent non-decaying oscillations may appear due to the parity-time symmetry of the cou...

Measurements of exciton transport using frequency-domain nearly degenerate four-wave mixing ~NDFWM! show a failure of Fick’s law and near-ballistic excitonic motion for scale lengths less than 10 mm. A solution of the Boltzmann transport equation assuming a simple momentum-changing collision model is in agreement with the observed NDFWM line shapes and apparent subquadratic dependence on invers...

The exciton binding energy serves as a critical criterion for identification of the nature of elementary excitations (neutral excitons versus a pair of charged carriers) in semiconductor materials. An exciton binding energy of 0.41 eV is determined experimentally for a selected nanotube type, the (8,3) tube, confirming the excitonic nature of the elementary excitations. This determination is ma...

The complexity induced by the Coulomb interaction between electrons determines the noninstantaneous character of exciton-exciton collisions. We show that the exciton-photon coupling in semiconductor microcavities is able to alter the exciton dynamics during collisions strongly affecting the effective scattering rates. Our analysis clarifies the origin of the great enhancement of parametric gain...

Electron-hole exchange interaction provides transverse (T) and longitudinal (L) characters of exciton. In homogeneous bulk crystal, exciton states are classified into T and L modes, and the T-mode exciton is optically active. However, T-mode exciton confined in quantum dot is optically forbidden. We classify exciton states confined in spherical and cylindrical quantum dots into L, T, and LT-mix...

Due to the long lifetime of indirect ~interwell! excitons, exciton condensation ~analogous to the BoseEinstein condensation of bosons! is expected to occur in coupled quantum wells ~CQW’s!. The critical conditions for the exciton condensation have been predicted to be strongly improved by high magnetic field perpendicular to the well plane. We present results of experimental study of transport ...

The photoluminescence (PL) and absorption experiments have been performed in GaSe slab with incident light polarized perpendicular to c-axis of sample at 10 K. An obvious energy difference of about 34 meV between exciton absorption peak and PL peak (the highest energy peak) is observed. By studying the temperature dependence of PL and absorption spectra, we attribute it to energy difference bet...