Electron Collimation in Twisted Bilayer Graphene via Gate-Defined Moiré Barriers

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Electronics

Background:

• Graphene p-n junctions enable electrostatic control of electron trajectories, similar to optical circuits.
• Twisted-bilayer graphene (tBLG) hosts novel correlated electronic phases, offering new avenues for quantum electronics research.
• Understanding and controlling electron flow in tBLG is crucial for developing advanced quantum devices.

Purpose of the Study:

• To demonstrate electron collimation in twisted-bilayer graphene (tBLG) using gate-defined moiré barriers.
• To investigate the role of moiré superlattice band-insulator gaps in controlling electron flow.
• To assess the efficiency of collimation by tuning junction properties and measuring transport.

Main Methods:

• Fabrication of a tBLG device with gate-defined moiré barriers.
• Utilizing the band-insulator gap of the moiré superlattice for electron collimation.
• Tuning single junctions to create combinations of pseudo and tunnel barriers.
• Measuring transport through two consecutive moiré collimators separated by 1 μm.

Main Results:

• Successful demonstration of electron collimation in tBLG via moiré barriers.
• Improved collimation efficiency achieved by tuning junction properties.
• Evidence of electron collimation in tBLG despite realistic twist-angle inhomogeneity.

Conclusions:

• Gate-defined moiré barriers effectively collimate electron flow in tBLG.
• This method provides a new tool for probing correlated electronic phases in tBLG.
• The demonstrated electron collimation in tBLG holds promise for future quantum electronic devices.