Influence of Exciton Dimensionality on Spectral Diffusion of Single-Walled Carbon Nanotubes

Abstract

We study temporal evolution of photoluminescence (PL) spectra from individual single-walled carbon nanotubes (SWCNTs) at cryogenic and room temperatures. Sublinear and superlinear correlations between fluctuating PL spectral positions and line widths are observed at cryogenic and room temperatures, respectively. We develop a simple model to explain these two different spectral diffusion behaviors in the framework of quantum-confined Stark effect (QCSE) caused by surface charges trapped in the vicinity of SWCNTs. We show that the wave function properties of excitons, namely, localization at cryogenic temperature and delocalization at room temperature, play a critical role in defining sub- and superlinear correlations. Room temperature PL spectral positions and line widths of SWCNTs coupled to gold dimer nanoantennas on the other hand exhibit sublinear correlations, indicating that excitonic emission mainly originates from nanometer range regions and excitons appear to be localized. Our numerical simulations show that such apparent localization of excitons results from plasmonic confinement of excitation and an enhancement of decay rates in the gap of the dimer nanoantennas.

Quantum dot-like excitonic behavior in individual single walled-carbon nanotubes

“…Note the red shift with increasing excitation power in Fig. 3 is a sign of quantum confined Stark effect (QCSE) as in 0D quantum emitters3132. Similarly we observed spectra with two peaks emerging above the original peak and an extra one at lower energy (shown in the SI), again indicating exciton localization.…”

Strain-Induced Trapping of Indirect Excitons in MoSe2/WSe2 Heterostructures

“…A representative PL spectrum of the heterostructure from a nanopillar site (Figure d) shows several discrete narrow peaks superimposed on the broad IX emission. Time-dependent PL spectral sequence of the peaks highlighted in Figure d shows significant PL spectral diffusion and blinking (Figure e), both characteristic of quantum emitters subject to local electric field flucturations. − We also investigate the effect of the nanopillar geometries on the IX emission by keeping a constant nanopillar height of 85 nm and varying their diameters from 50 to 300 nm. We find that in the height-to-diameter aspect ratio range of 0.3 to 0.8, distinct narrow IX peaks can be well resolved, although there is no clear correlation between the number of narrow peaks per site and the nanopillar aspect ratio.…”

Ubiquity of Exciton Localization in Cryogenic Carbon Nanotubes

“…As for the nanotube in Figure 2 a, we assigned the chirality to individual CNTs of our experiments using their room temperature PL emission energy 2 , 32 and allowing energy offsets of the order of 10–20 meV to account for the tube-to-tube variations in the effective dielectric environment 37 − 39 which may stem from an inhomogeneous tube coverage by surfactant, 15 water-filling of CNTs dispersed from aqueous suspensions, 40 or local charges in the nearby substrate. 35 , 41 , 42 …”