X. Tian, Q. Gu, J. Duan, R. Chen, H. Liu, Y. Hou and J. Chen
Nanoscale 10, 6288 (2018)
We realized the real-space imaging of Luttinger-liquid plasmons in semiconducting single-walled carbon nanotubes (s-SWCNTs) and studied the effects of chemical-doping-induced charge carrier density modulation on plasmons. Using scattering-type scanning near-field optical microscopy (s-SNOM), we compared the Luttinger-liquid plasmonic behavior in pre- and post-HNO3-doped SWCNTs. Raman measurements revealed that the physical mechanism is P-type doping. Through HNO3 doping, we effectively increased the charge carrier density in s-SWCNTs and achieved quantum plasmons simultaneously with strong confinement (l0⁄lp ≈ 70) and high quality factor (Q ≈ 20). The combination of high quality factor and strong subwavelength confinement in Luttinger-liquid plasmons is critical to the future application of plasmonic devices.