Mechanically-tunable bandgap closing in 2D graphene phononic crystals

Area of Science:

• Condensed Matter Physics
• Materials Science
• Acoustics

Background:

• Phononic crystals are engineered structures that control the propagation of mechanical vibrations.
• Tunable phononic devices are crucial for advanced applications in acoustics and quantum technologies.
• Existing phononic systems often lack robust tunability and real-world applicability.

Purpose of the Study:

• To design and simulate a phononic crystal with tunable mechanical conductivity.
• To demonstrate a phononic transistor capable of switching between insulating and conductive states.
• To explore the potential of this system for phonon logic and mechanical quantum applications.

Main Methods:

• Simulations of a phononic lattice under varying biaxial and uniaxial tension.
• Design of a finite-sized graphene-based phononic crystal device tuned by gate voltage.
• Analysis of acoustic transmission measurements to probe bandgap closing and phononic bandgap persistence.

Main Results:

• A tunable phononic bandgap was identified and controllable via tension uniaxiality.
• The system demonstrated a high on/off ratio (10^5) for MHz-phonons, functioning as a phononic transistor.
• The phononic bandgap remained robust against surface contaminants and tension variations.

Conclusions:

• The proposed tunable phononic crystal offers a novel approach to controlling mechanical vibrations.
• This system serves as a mechanical analogue to a metal-insulator transition, enabling tunable coupling.
• The device is a promising extension for phonon logic applications and mechanical quantum systems.