Abstract
We theoretically study the optical response of single-walled carbon nanotubes (SWNTs) under high-intensity laser irradiation. Due to the quasi-one-dimensional structure of SWNTs, the Coulomb interaction between excitons is enhanced relative to the bulk. As a result, excitons can be ionized to electrons and holes by the Auger ionization process under high-intensity laser irradiation. Taking into account the effect of Auger-ionized carriers, we calculate absorption spectra by solving the Bethe–Salpeter equation in the tight-binding approximation. We found that Auger-ionized carriers induce a band-gap renormalization and a bleaching of excitons, leading to a nonlinear optical response. Our calculation reveals the strong influence of Auger-ionized carriers on excitons under high-intensity laser irradiation, which may unravel the recently observed nonlinear behavior of photoluminescence emission spectra.
Highlights
Electron Hole properties of single-walled carbon nanotubes (SWNTs) by considering many-body effects of excitons induced by the surrounding electron–hole carriers
Before we present below the calculated absorption spectra, we first briefly describe the implications of the theory described in the previous section
Assuming that all the excitons lost in the Auger process are ionized to form electron–hole carriers, we can roughly estimate the ionized carrier density to be of order of the 10−3 nm−1 for a 1 μm long SWNT, which is derived by subtracting the exciton number at the pump fluence where the saturation starts from the one at the pump fluence where the decline starts
Summary
Electron Hole properties of SWNTs by considering many-body effects of excitons induced by the surrounding electron–hole carriers. Dissociation is unlikely to be induced by thermal agitation because excitons have large binding energies in SWNTs. Instead, we focus on the fact that the Auger process can dissociate excitons into ionized electron–hole pairs. Our calculations demonstrate that Auger-ionized carriers can give rise to a nonlinear optical response, which may be the origin of the interesting behavior observed under intense laser irradiation.
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