Ultra-narrow-band near-infrared thermal exciton radiation in intrinsic one-dimensional semiconductors

Abstract

Thermal radiation is the most primitive light emission phenomenon of materials. Broadband radiation from red-hot materials is well known as the kick-starter phenomenon of modern quantum physics in the early twentieth century; even nowadays, its artificial control plays a central role in modern science and technology. Herein, we report the fundamental thermal radiation properties of intrinsic one-dimensional semiconductors and metals, which have not been elucidated because of significant technical challenges. We observed narrow-band near-infrared radiation from semiconducting single-walled carbon nanotubes at 1000–2000 K in contrast to its broadband metallic counterpart. We confirm that the ultra-narrow-band radiation is enabled by the thermal generation of excitons that are hydrogen-like neutral exotic atoms comprising mutually bound electrons and holes. Our findings uncover the robust quantum correlations in intrinsic one-dimensional semiconductors even at 2000 K; additionally, the findings provide an opportunity for excitonic optothermal engineering toward the realization of efficient thermophotovoltaic energy harvesting.

Strength of carbon nanotubes depends on their chemical structures

“…Broadband Rayleigh scattering spectroscopy was employed to determine the nanotube structures (Fig. 2b; see Methods and Supplementary Table 1) 26,27 . Then, the individual structure-defined nanotubes were picked up with a micro fork (Fig.…”

“…Rayleigh spectroscopy has been used previously as a powerful method to probe the optical transitions in the photon energy range above 1.2 eV, which is limited by the detectable range of commonly used silicon-based detectors 33,35–40 . Since the lack of spectral information below 1.2 eV often yields uncertainties in the nanotube structure assignment 35,38,39 , we expanded the detection range to 0.8 eV using a near-infrared detector, which reduced the uncertainties and yielded considerable improvements in the accuracy and efficiency of the structure assignment process (broadband Rayleigh spectroscopy) 27 . Supplementary Fig.…”

Theory of exciton thermal radiation in semiconducting single-walled carbon nanotubes

“…A SWCNT is a cylindrically rolled-up graphene sheet, and it is regarded as a quasi-one-dimensional (1D) system with a pronounced quantum confinement effect. Narrowband near-infrared thermal radiation from an individual semiconducting SWCNT was recently reported [37]. This was enabled by the thermal generation of excitons, which are exotic atoms composed of a mutually bound electron-hole pairs.…”

“…For a semiconductor photonic crystal, both the photonic bandgap and the electronic bandgap make strong contributions to fine spectral control [18][19][20]. The use of exciton resonance in semiconducting single-walled carbon nanotubes (SWCNTs) has also been recently proposed as a new approach [37]. A SWCNT is a cylindrically rolled-up graphene sheet, and it is regarded as a quasi-one-dimensional (1D) system with a pronounced quantum confinement effect.…”

“…In addition, the exciton resonance is tunable by control of the structure (the diameter and/or chiral angle), which is specified by two integers known as the chiral indices (n, m). Furthermore, SWCNT excitons and SWCNTs themselves are stable even at temperatures as high as 2000 K [37], due to their large binding energies [38][39][40] and stable s p 2 covalent bonding [42], respectively. These features are quite promising for the use of SWCNTs under high-temperature conditions.…”