Intraband and intersubband many-body effects in the nonlinear optical response of single-wall carbon nanotubes

Abstract

We report on the nonlinear optical response of a mono-chiral sample of (6,5) single-wall carbon nanotubes by means of broad-band two-color pump-probe spectroscopy with selective excitation of the S11 excitons. By using a moment analysis of the transient spectra, we show that all the nonlinear features can be accurately accounted for by elementary deformations of the linear absorption spectrum. The photo-generation of S11 excitons induces a broadening and a blue shift of both the S11 and S22 excitonic transitions. In contrast, only the S11 transition shows a reduction of oscillator strength, ruling out population up-conversion. These nonlinear signatures result from many-body effects, including phase-space filling, wave-function renormalization and exciton collisions. This framework is sufficient to interpret the magnitude of the observed nonlinearities and stress the importance of intersubband exciton interactions. Remarkably, we show that these intersubband interactions have the same magnitude as the intraband ones and bring the major contribution to the photo-bleaching of the S22 excitonic transition upon S11 excitation through energy shift and broadening.

Probing the ultrafast dynamics of excitons in single semiconducting carbon nanotubes

“…We note that for delay times between 10 and 100 ps the pump-probe transients could also be described by the t −1/2 decay reported in TA literature attributed to EEA 19 , 25 . This decay function, however, cannot describe the initial time dependence.…”

“…Since the discovery of SWCNTs a large number of studies addressed the excited state dynamics of SWCNTs on the ensemble level. By probing transient changes in the sample's transmission and not relying on spontaneous emission, these studies revealed the dynamics of a larger series of photoinduced states including biexcitons and trions as well as triplet excitons 2,13,[16][17][18][19][20][21][22] . In TA, the main signal contributions result from ground state bleaching related to phase-space filling, stimulated emission and absorption from photo-generated states.…”

“…For very high fluences a cross-over between diffusion and reaction-limited EEA at about 3 ps was reported 25 . For longer time scales several TA studies describe the exciton dynamics only by t −1/2 decay that results from the diffusive character of non-radiative decay at charged impurities 30 or two-particle interactions leading to EEA 19,25 without the exponential decay components as observed in timeresolved PL experiments [7][8][9][10] .…”

Hot Exciton Relaxation and Exciton Trapping in Single-Walled Carbon Nanotube Thin Films

“…A spectroscopic tool that can distinguish different excited states and quantify the rate of energy dissipation is critical to understand these processes. Transient absorption spectroscopy and time-resolved photoluminescence spectroscopy have been widely used to study the excited state dynamics in s-SWCNTs. ,,,− However, distinguishing different excited states using these methods can be challenging. Important quantities such as the amount of excess energy carried by hot excitons cannot be obtained directly using these techniques.…”

Diffusive and Unimolecular Nonradiative Decay of Excited States in Doped Carbon Nanotubes

“…15,22,23 Such models were particularly successful in describing the dependence of fluorescence quantum yields in SWNTs on nanotube length, 15,[23][24][25][26] the effect of impurities on PL-imaging of SWNTs 27,28 or the influence of diffusive exciton transport on NR decay observed in time-domain investigations of exciton dynamics. 22,[29][30][31][32] Moreover, localization of excess charge carriers has also been instrumental for the interpretation of Breit-Wigner-Fano resonances in the IR spectra of doped SWNTs. 33,34 Here, we present findings in favor of inhomogeneous NR decay of excitons and trions in doped s-SWNTs.…”