Author Correction: Carbon nanotubes as emerging quantum-light sources.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Publisher Correction: Carbon nanotubes as emerging quantum-light sources.

In the version of this Perspective originally published, the x-axis label of Fig. 1d was missing; it should have read 'Wavelength (nm)'. The units of the y axis of Fig. 3b were incorrect; they should have been meV. And the citation of Fig. 3c in the main text was incorrect; it should have been to Fig. 3b. These issues have now been corrected.

Carbon nanotubes as emerging quantum-light sources.

Progress in quantum computing and quantum cryptography requires efficient, electrically triggered, single-photon sources at room temperature in the telecom wavelengths. It has been long known that semiconducting single-wall carbon nanotubes (SWCNTs) display strong excitonic binding and emit light over a broad range of wavelengths, but their use has been hampered by a low quantum yield and a high sensitivity to spectral diffusion and blinking. In this Perspective, we discuss recent advances in the mastering of SWCNT optical properties by chemistry, electrical contacting and resonator coupling towards advancing their use as quantum light sources. We describe the latest results in terms of single-photon purity, generation efficiency and indistinguishability. Finally, we consider the main fundamental challenges stemming from the unique properties of SWCNTs and the most promising roads for SWCNT-based chip integrated quantum photonic sources.

Photoinduced dynamics in cycloparaphenylenes: planarization, electron-phonon coupling, localization and intra-ring migration of the electronic excitation.

Cycloparaphenylenes represent the smallest possible fragments of armchair carbon nanotubes. Due to their cyclic and curved conjugation, these nanohoops own unique photophysical properties. Herein, the internal conversion processes of cycloparaphenylenes of sizes 9 through 16 are simulated using Non-Adiabatic Excited States Molecular Dynamics. In order to analyze effects of increased conformational disorder, simulations are done at both low temperature (10 K) and room temperature (300 K). We found the photoexcitation and subsequent electronic energy relaxation and redistribution lead to different structural and electronic signatures such as planarization of the chain, electron-phonon couplings, wavefunction localization, and intra-ring migration of excitons. During excited state dynamics on a picosecond time-scale, an electronic excitation becomes partially localized on a portion of the ring (about 3-5 phenyl rings), which is not a mere static contraction of the wavefunction. In a process of non-radiative relaxation involving non-adiabatic transitions, the latter exhibits significant dynamical mobility by sampling uniformly the entire molecular structure. Such randomized migration involving all phenyl rings, occurs in a wave-like fashion coupled to vibrational degrees of freedom. These results can be connected to unpolarized emission observed in single-molecule fluorescence experiments. Observed intra-ring energy transfer is subdued for lower temperatures and adiabatic dynamics involving low-energy photoexcitation to the first excited state. Overall our analysis provides a detailed description of photo excited dynamics in molecular systems with circular geometry, outlines size-dependent trends and connotes specific spectroscopic signatures appearing in time-resolved experimental probes.

Strong and ductile colossal carbon tubes with walls of rectangular macropores.

We report a new type of carbon material-porous colossal carbon tubes. Compared with carbon nanotubes, colossal carbon tubes have a much bigger size, with a diameter of between 40 and 100 mum and a length in the range of centimeters. Significantly, the walls of the colossal tubes are composed of macroscopic rectangular columnar pores and exhibit an ultralow density comparable to that of carbon nanofoams. The porous walls of colossal tubes also show a highly ordered lamellar structure similar to that of graphite. Furthermore, colossal tubes possess excellent mechanical and electrical properties.

Single carbon nanotubes probed by photoluminescence excitation spectroscopy: the role of phonon-assisted transitions.

We study light absorption mechanisms in semiconducting carbon nanotubes using low-temperature, single-nanotube photoluminescence excitation spectroscopy. In addition to purely electronic transitions, we observe several strong phonon-assisted bands due to excitation of one or more phonon modes together with the first electronic state. In contrast with a small width of emission lines (sub-meV to a few meV), most of the photoluminescence excitation features have significant linewidths of tens of meV. All of these observations indicate very strong electron-phonon coupling that allows efficient excitation of electronic states via phonon-assisted processes and leads to ultrafast intraband relaxation due to inelastic electron-phonon scattering.

Ultralong single-wall carbon nanotubes.

Since the discovery of carbon nanotubes in 1991 by Iijima, there has been great interest in creating long, continuous nanotubes for applications where their properties coupled with extended lengths will enable new technology developments. For example, ultralong nanotubes can be spun into fibres that are more than an order of magnitude stronger than any current structural material, allowing revolutionary advances in lightweight, high-strength applications. Long metallic nanotubes will enable new types of micro-electromechanical systems such as micro-electric motors, and can also act as a nanoconducting cable for wiring micro-electronic devices. Here we report the synthesis of 4-cm-long individual single-wall carbon nanotubes (SWNTs) at a high growth rate of 11 microm s(-1) by catalytic chemical vapour deposition. Our results suggest the possibility of growing SWNTs continuously without any apparent length limitation.

Low temperature emission spectra of individual single-walled carbon nanotubes: multiplicity of subspecies within single-species nanotube ensembles.

Low-temperature photoluminescence (PL) studies of individual semiconducting single-walled carbon nanotubes reveal ultranarrow peaks (down to 0.25 meV linewidths) that exhibit blinking and spectral wandering. Multiple peaks appear within bands previously assigned to nanotubes of certain chiralities, indicating the existence of numerous subspecies within single-chirality specimens. The sharp PL features show two types of distinctly different shapes (symmetric versus asymmetric) and temperature dependences (weak versus strong), which we attribute to the presence of unintentionally doped nanotubes along with undoped species.