Intrinsically Ultrastrong Plasmon-Exciton Interactions in Crystallized Films of Carbon Nanotubes*

We show that carbon nanotubes can be crystallized into chip-scale, two-dimensionally ordered films and that this new material enables intrinsically ultrastrong emitter-cavity interactions: rather than interacting with external cavities, nanotube excitons couple to the near-infrared plasmon resonances of the nanotubes themselves [1]. Our polycrystalline nanotube films have a hexagonal crystal structure, ~25 nm domains, and a 1.74 nm lattice constant. With this extremely high nanotube density and nearly ideal plasmon-exciton spatial overlap, plasmon-exciton coupling strengths reach 0.5 eV, which is 75% of the bare exciton energy and a near record for room-temperature ultrastrong coupling. Crystallized nanotube films provide a compelling foundation for high-ampacity conductors, low-power optical switches, and tunable optical antennas.
[1] Ho et al, Proc. Natl. Ac. Sci., accepted (2018)