Screening is limited in single-walled carbon nanotubes because of their one-dimensional nature, and the strong Coulomb interactions result in optical spectra dominated by excitons with binding energies lager than half an eV. Also because of the limited screening, a charged carrier can be bound to an exciton to form a trion that is stable at room temperature. In particular, air-suspended nanotubes exhibit pronounced effects because of reduced environmental screening [1,2], where adsorption and desorption of molecules on the surface of nanotubes can readily modulate such interactions.

Here we show that large screening effects on excitonic energies can cause laser-induced optical bistability [3]. Molecular desorption can occur with sufficient heating by laser, which in turn results in significant blueshift of exciton emission wavelength. When the excitation is detuned to a higher energy shoulder of the E22 absorption resonance, we observe abrupt transition and hysteretic behavior of emission wavelength in the excitation power dependence. We explain the bistability by simultaneous shifts of absorption and emission resonances, and perform time-resolved measurements to obtain relevant time scales.

Work supported by JSPS (KAKENHI JP26610080, JP16H05962), The Canon Foundation, and MEXT (Photon Frontier Network Program, Nanotechnology Platform).

[1] T. Uda, M. Yoshida, A. Ishii, Y. K. Kato, Nano Lett. 16, 2278 (2016).
[2] M. Yoshida, A. Popert, Y. K. Kato, Phys. Rev. B 93, 041402(R) (2016).
[3] T. Uda, A. Ishii, Y. K. Kato, in preparation.