Phonon lateral confinement enables thermal rectification in asymmetric single-material nanostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Thermal rectification (TR) is crucial for thermal management.
• Existing TR mechanisms are typically observed in macroscopic heterojunctions.

Purpose of the Study:

• To elucidate the fundamental mechanism of thermal rectification in asymmetric graphene nanoribbons (GNRs).
• To investigate the role of lateral confinement in enabling TR at the nanoscale.
• To explore the potential of other asymmetric nanostructures as thermal rectifiers.

Main Methods:

• Molecular dynamics simulations to study TR in GNRs of varying widths.
• Solving the heat diffusion equation to analyze heat transport in bulk materials.
• Phonon spectra analysis to understand the underlying physical mechanisms.

Main Results:

• TR in asymmetric GNRs is driven by phonon confinement, a new mechanism distinct from macroscopic systems.
• TR diminishes with increasing GNR width, becoming negligible in bulk materials.
• Phonon lateral confinement enables TR through spectral overlap, space-dependent thermal conductivity, and edge localization.

Conclusions:

• Lateral phonon confinement is essential for achieving significant thermal rectification in single-material nanostructures.
• Asymmetric nanostructures like nanowires, thin films, and quantum dots are promising candidates for high-performance thermal rectifiers.