Prolonged spontaneous emission and dephasing of localized excitons in air-bridged carbon nanotubes

TL;DR

This study reveals intrinsic exciton photophysics in air-bridged carbon nanotubes with significantly prolonged emission and dephasing times, advancing understanding for optoelectronic applications.

Contribution

It provides the first direct measurement of intrinsic exciton emission and decoherence times in ultra-clean, air-bridged carbon nanotubes, surpassing prior extrinsic-effect-limited results.

Findings

Prolonged spontaneous emission time up to 18 ns.

Exciton decoherence time up to 2.1 ps.

Intrinsic exciton dynamics observed in ultra-clean nanotubes.

Abstract

The bright exciton emission of semiconducting carbon nanotubes is appealing for optoelectronic and quantum photonic devices as well as fundamental studies of light-matter interaction in one-dimensional nanostructures. The photophysics of excitons in carbon nanotubes till date is however largely affected by extrinsic effects of the dielectric environment. Here we carried out time-resolved photoluminescence measurements over 14 orders of magnitude for ultra-clean carbon nanotubes bridging an airgap over pillar posts. Our measurements demonstrate a new regime of intrinsic exciton photophysics with prolonged spontaneous emission times up to T1=18 ns, between one to two orders of magnitude better than prior measurements and in agreement with values first hypothesized by theorists about a decade ago. Further we establish for the first time the exciton decoherence times of individual nanotubes in the time-domain and found four-fold prolonged values up to T2=2.1 ps compared to ensemble measurements. These first observations motivate new discussions about the magnitude of the intrinsic dephasing mechanism while the prolonged exciton dynamics is promising for device applications.