Intrinsically ultrastrong plasmon-exciton interactions in crystallized films of carbon nanotubes

TL;DR

This paper demonstrates that crystallized carbon nanotube films exhibit intrinsically ultrastrong plasmon-exciton interactions, achieving near-record coupling strengths at room temperature, which could enable advanced nanophotonic applications.

Contribution

It introduces a new material platform of crystallized nanotube films with ultrastrong plasmon-exciton coupling, surpassing previous external cavity-based systems.

Findings

Achieved plasmon-exciton coupling strength of 0.5 eV

Crystallized nanotube films have hexagonal structure with ~25 nm domains

Coupling strength is 75% of the exciton energy at room temperature

Abstract

In cavity quantum electrodynamics, optical emitters that are strongly coupled to cavities give rise to polaritons with characteristics of both the emitters and the cavity excitations. 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. 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 represent a milestone in nanomaterials assembly and provide a compelling foundation for high-ampacity conductors, low-power optical switches, and tunable optical antennas.