Terahertz generation and chaotic dynamics in single-walled zigzag carbon nanotubes

Area of Science:

• Physics
• Materials Science
• Nonlinear Dynamics

Background:

• Semiconducting carbon nanotubes exhibit unique electronic properties.
• Negative differential velocity in carbon nanotubes can lead to current oscillations.
• Understanding nonlinear dynamics is crucial for advanced electronic devices.

Purpose of the Study:

• To investigate self-sustained terahertz current oscillation and chaotic dynamics in semiconducting single-walled zigzag carbon nanotubes.
• To analyze the influence of external AC voltage on nonlinear oscillatory modes.
• To explore the transitions between periodic and chaotic states.

Main Methods:

• Utilized time-dependent drift diffusion equations for numerical simulations.
• Applied external high-frequency AC voltage superimposed on a DC bias.
• Employed chaos-detecting methods including bifurcation diagrams, phase portraits, first return maps, and Fourier spectra.

Main Results:

• Observed self-sustained terahertz current oscillation driven by negative differential velocity.
• Identified various nonlinear oscillatory modes (periodic and chaotic) under varying AC driving amplitudes.
• Demonstrated complex transitions between periodic and chaotic states controlled by driving amplitude.

Conclusions:

• The competition between natural and external driving oscillations dictates the appearance of different nonlinear modes.
• Carbon nanotubes exhibit rich nonlinear dynamics, including chaos, under specific voltage conditions.
• Bifurcation diagrams effectively illustrate the complex transitions in these systems.