Department of Physics, Stevens Institute of Technology, Hoboken, New Jersey 07030, USA.
Nat Commun. 2013;4:2152. doi: 10.1038/ncomms3152.
The bright exciton emission of carbon nanotubes is appealing for optoelectronic devices and fundamental studies of light-matter interaction in one-dimensional nanostructures. However, to date, the photophysics of excitons in carbon nanotubes is largely affected by extrinsic effects. Here we perform time-resolved photoluminescence measurements over 14 orders of magnitude for ultra-clean carbon nanotubes bridging an air gap over pillar posts. Our measurements demonstrate a new regime of intrinsic exciton photophysics with prolonged spontaneous emission times up to T1=18 ns, about two orders of magnitude better than prior measurements and in agreement with values hypothesized by theorists about a decade ago. Furthermore, we establish for the first time exciton decoherence times of individual nanotubes in the time domain and find fourfold prolonged values up to T2=2.1 ps compared with ensemble measurements. These first observations motivate new discussions about the magnitude of the intrinsic dephasing mechanism while the prolonged exciton dynamics is promising for applications.
碳纳米管的明亮激子发射对于光电设备和一维纳米结构中光与物质相互作用的基础研究很有吸引力。然而，迄今为止，碳纳米管中激子的光物理性质在很大程度上受到了外在因素的影响。在这里，我们在空气隙上的支柱柱之间桥接的超洁净碳纳米管上进行了 14 个数量级的时间分辨光致发光测量。我们的测量结果表明，存在一种新的本征激子光物理状态，其自发发射时间延长至 T1=18 ns，比以前的测量结果好两个数量级，与大约十年前理论家假设的值一致。此外，我们首次在时域内建立了单个碳纳米管的激子退相干时间，并发现与整体测量相比，其值延长了四倍，达到 T2=2.1 ps。这些首次观察结果激发了关于本征退相干机制幅度的新讨论，而延长的激子动力学则为应用提供了广阔的前景。
