Supercurrent mediated by helical edge modes in bilayer graphene.

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Bilayer graphene encapsulated in WSe2 exhibits a weak topological phase with helical edge states.
• This system is tunable and offers a platform for studying topological superconductivity without magnetic fields.

Purpose of the Study:

• To investigate topological superconductivity in a tunable bilayer graphene-tungsten diselenide heterostructure.
• To explore the emergence and effects of helical edge states in a Josephson geometry.

Main Methods:

• Coupling helical edges of the heterostructure to a superconductor.
• Utilizing superconducting quantum interferometry to analyze Josephson junctions.
• Theoretical modeling to explain observed phenomena.

Main Results:

• Observed suppression of critical current in Josephson geometry due to bulk gap inversion and helical states.
• Detected an even-odd effect in the Fraunhofer interference pattern within the inverted gap phase.
• Confirmed the effect arises from helical modes connecting sample edges.

Conclusions:

• The observed even-odd effect is a signature of helical modes in the topological phase.
• The suppression of the critical current and interference pattern demonstrate the topological nature of the inverted gap.
• This work highlights the potential of engineered heterostructures for realizing novel quantum phenomena.