講演情報
[20p-A602-9]Elucidating Upconversion Photoluminescence Mechanisms in Air-Suspended Single-Walled Carbon Nanotubes
〇Daichi Kozawa1,2,3, Yuichiro K. Kato1,2 (1.RAP, RIKEN, 2.CPR, RIKEN, 3.MANA, NIMS)
キーワード：
carbon nanotubes、upconversion photoluminescence、phonons
In this study, we elucidate the high-efficiency UCPL in air-suspended single-walled carbon nanotubes (SWNTs). UCPL is detected even in individual SWNTs despite the sizeable energy separation between the emission energy and excitation energy. We conduct power dependence of UCPL intensity and observe linear response, ruling out two-photon excitation as an upconversion source. Our exhaustive exploration of UCPL spectra across various chiralities highlights the universal presence of this upconversion process and energy separation dependence of UCPL intensity. In conducting upconversion photoluminescence excitation (UCPLE) spectroscopy across a broad range of energy separations, we discern UCPLE peaks as sidebands of K-momentum dark excitons where specific phonon modes at the K point are involved [3]. The high efficiency of the upconversion process can be attributed to the one-phonon process and the abundance of low-energy phonons. To better interpret these findings, we develop a physical model of exciton-phonon scattering which successfully reproduces UCPLE spectra. This model also allows for deducing phonon energies and relative amplitudes of matrix element by fit to the UCPLE spectra. Additionally, our model accurately predicts the temperature dependence of UCPLE spectra. By clarifying the complexities of the upconversion phenomena in SWNTs, this study holds the potential to drive development in nanotube-based device applications.