High harmonic generation in armchair carbon nanotubes

Area of Science:

• Condensed Matter Physics
• Quantum Optics
• Materials Science

Background:

• High-order harmonic generation (HHG) is a key nonlinear optical process.
• Carbon nanotubes (CNTs) exhibit unique electronic properties relevant to light-matter interactions.
• Previous studies explored HHG in 2D materials like graphene.

Purpose of the Study:

• Investigate HHG in armchair single-wall carbon nanotubes (SWNTs) using mid-infrared laser pulses.
• Analyze the dominant harmonic bands and cutoff frequency behavior.
• Compare HHG mechanisms in SWNTs with those in graphene.

Main Methods:

• Theoretical study of HHG in armchair SWNTs.
• Numerical simulations of electron dynamics under intense laser fields.
• Analysis of band structure and van Hove singularities.

Main Results:

• HHG in (n, n) SWNTs is dominated by |m| = n-1 bands.
• The HHG cutoff frequency saturates with laser intensity, similar to graphene.
• SWNT HHG can be modeled as a 1D periodic system, tunable via structural parameters.
• Electron-hole excitation involves non-adiabatic crossing of van Hove singularities, differing from graphene's Dirac point crossing.

Conclusions:

• HHG in SWNTs exhibits 1D characteristics, offering control over high-frequency emission.
• The mechanism shares similarities with graphene but is distinguished by van Hove singularity interactions.
• Structural parameter control is crucial for tailoring HHG in SWNTs for potential applications.