Condensed-Matter Physics & Materials Science Seminar

Carbon nanotubes (CNTs) have remarkable optical properties due to
the electron-hole confinement in 1D, with important implications in
nanophotonics. The absorption spectra is dominated by excitons,
which properties depend on the dielectric constant of the embedding
material [1]. The exciton-phonon interactions determines the fast
decay of second E22 exciton and leads to a phonon sideband signature
200-210 meV above the zero-phonon line, which provides a signature
of the excitonic character [2]. We calculate the exciton radiative
lifetime, which in turn determines the efficiency of opto-electronic
CNT devices. We predict an unusual nonmonotonic temperature
dependence, due to optically inactive "dark" exciton bands below the
optically active "bright" exciton [3]. The dark exciton can be
"brightened" by the applied magnetic field [4]. The field
accelerated carriers can efficiently produce excitons via the impact
excitation scattering mechanism, which produces locally high density
of excitons giving rise to the ultra bright nano light sources
[5,6]. The electric field leads to the exciton ionization, Stark
shift of the exciton energy, and Franz-Keldysh oscillations in the
absorption spectra [7].