We have performed momentum dependent electron energy-loss studies of the electronic excitations in sexithiophene and compared the results to those from parent oligomers. Our experiment probes the dynamic structure factor S(q, ω) and we show that the momentum dependent intensity variation of the excitations observed can be used to extract the size of the electron-hole pair created in the excitat...

We report on the excitation energy dependence of the inner ring in the exciton emission pattern. The contrast of the inner ring is found to decrease with lowering excitation energy. Excitation by light tuned to the direct exciton resonance is found to effectively suppress excitation-induced heating of indirect excitons and facilitate the realization of a cold and dense exciton gas. The excitati...

We demonstrate the possibility of room-temperature, thermal equilibrium Bose-Einstein condensation (BEC) of exciton-polaritons in a multiple quantum well (QW) system composed of InGaAs quantum wells surrounded by InP barriers, allowing for the emission of light near telecommunication wavelengths. The QWs are embedded in a cavity consisting of double slanted pore (SP2) photonic crystals composed...

In the framework of effective mass approximation, negative and positive trions, exciton, biexciton states are investigated in strongly prolate ellipsoidal quantum dots by variational method. Since dot has a character, all excitonic complexes considered quasi-one-dimensional. As such system, analytical solution does not exist for many-particle problem, it is solved The trial variation functions ...

A theoretical model to determine the properties of an exciton confined in a semiconductor quantum box with rectangular potential is presented. We have used two-band and effective mass approximation. The approach includes considerable analytic phase makes it possible reduce numerical calculations. According new formulation, limit cases for bulk two-dimensional structure are deduced, good agreeme...

Excitonic effects are crucial to optical properties, and the exciton binding energy E(b) in technologically important semiconductors varies from merely a few meV to about 100 meV. This large variation, however, is not well understood. We investigate the relationship between the electronic band structures and exciton binding energies in semiconductors, employing first-principles calculations bas...

The exciton binding energy (EBE) in CdSe quantum dots (QDs) has been determined using X-ray spectroscopy. Using X-ray absorption and photoemission spectroscopy, the conduction band (CB) and valence band (VB) edge shifts as a function of particle size have been determined and combined to obtain the true band gap of the QDs (i.e., without an exciton). These values can be compared to the excitonic...

We present a first-principles calculation of the optical properties of armchair-edged graphene nanoribbons (AGNRs) with many-electron effects included. The reduced dimensionality of the AGNRs gives rise to an enhanced electron-hole binding energy for both bright and dark exciton states (0.8-1.4 eV for GNRs with width approximately 1.2 nm) and dramatically changes the optical spectra owing to a ...

We evaluate binding energies of trions X±, excitons bound by a donor or acceptor charge X^{D(A)}, and overcharged acceptors or donors in two-dimensional atomic crystals by mapping the three-body problem in two dimensions onto one particle in a three-dimensional potential treatable by a purposely developed boundary-matching-matrix method. We find that in monolayers of transition metal dichalcoge...