We report the intriguing dynamics of a potassium ion interacting with a 16 Å carbon nanotube. The ion induces a strong dielectric response in the nanotube wall that can be described through a self-consistent tight-binding method. The polarization of the nanotube was found to play a critical role in the ion-nanotube interaction, which exhibits a low access barrier of only $1.05\mathrm{kcal}/\mathrm{mol}$ and a deep, attractive well with a depth of about $30\mathrm{kcal}/\mathrm{mol}$. An ion bound in the nanotube is predicted to oscillate at a frequency of about 0.4 terahertz, dragging the electrons of the nanotube along. Besides its appealing nature in low-dimensional physics, such a nano-oscillator may serve as a room temperature terahertz wave detector.

• Received 4 July 2005

DOI:https://doi.org/10.1103/PhysRevLett.95.246801