Mode coupling and resonance-induced relaxation in carbon nanotubes

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Vibrational mode relaxation in low-dimensional materials is crucial for thermal transport and nanomechanical resonator design.
• Understanding intrinsic relaxation dynamics is essential for controlling mechanical coherence.

Purpose of the Study:

• Investigate intrinsic relaxation dynamics of armchair carbon nanotubes (CNTs) under single-mode excitation.
• Provide a symmetry-based description of the vibrational spectrum at the Brillouin-zone center.
• Uncover the mechanisms governing intermodal coupling and energy redistribution.

Main Methods:

• Employed molecular dynamics (MD) simulations combined with Floquet stability analysis.
• Classified zone-center modes by azimuthal quantum number and inversion parity.
• Utilized the theory of bushes of normal modes and constructed monodromy matrices.

Main Results:

• Identified symmetry-based selection rules for intermodal coupling and early-time energy redistribution.
• Discovered that multiwave resonances (three-wave and four-wave processes) are the primary drivers of excited mode relaxation.
• Demonstrated that Floquet multipliers accurately predict resonance-induced instabilities and relaxation times.

Conclusions:

• Established a unified microscopic understanding of intrinsic relaxation in CNTs.
• Highlighted the critical role of multiwave resonances in vibrational mode decay.
• Suggested strategies for designing nanoscale systems with robust vibrational modes and controlled intermodal coupling.