Direct visualization of relativistic quantum scars in graphene quantum dots

Area of Science:

• Quantum physics
• Condensed matter physics
• Mesoscopic physics

Background:

• Quantum scars are eigenstates with enhanced probability density along unstable classical periodic orbits.
• They defy ergodicity in chaotic quantum systems, but direct visualization has been challenging.
• Understanding quantum scars is crucial for quantum-classical correspondence.

Purpose of the Study:

• To directly visualize quantum scars in a real quantum system.
• To investigate the nature of quantum scarring in relativistic systems.
• To bridge the gap between theoretical predictions and experimental observations of quantum scars.

Main Methods:

• Utilized in situ graphene quantum dot (GQD) creation.
• Employed a wavefunction mapping technique with scanning tunnelling microscopy.
• Combined classical and quantum simulations for analysis.

Main Results:

• Successfully imaged quantum scars for Dirac electrons in stadium-shaped GQDs with nanometre resolution.
• Observed lemniscate (∞-shaped) and streak-like enhanced probability densities.
• Confirmed these patterns correspond to unstable periodic orbits, providing visual evidence of quantum scarring.

Conclusions:

• Provided the first direct visualization of quantum scars in a relativistic chaotic system.
• Demonstrated the link between observed scar patterns and specific unstable periodic orbits.
• Opened avenues for experimental studies of various quantum scarring phenomena.