Tailoring Pure Valley-Zeeman Spin-Orbit Coupling in WSe_{2}-Encapsulated Monolayer Graphene

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Phenomena

Background:

• Van der Waals heterostructures offer tunable electronic properties through proximity effects.
• Controlling spin-orbit coupling (SOC) in graphene is crucial for spintronic applications.
• Experimental realization of predicted quantum interference effects in encapsulated graphene has been challenging.

Purpose of the Study:

• To experimentally achieve and investigate pure valley-Zeeman spin-orbit coupling in monolayer graphene.
• To explore the influence of twisted transition metal dichalcogenide encapsulation on graphene's electronic properties.
• To demonstrate the tunability of proximity-induced spin-orbit coupling.

Main Methods:

• Encapsulation of monolayer graphene between two parallel twisted tungsten diselenide (WSe₂) monolayers.
• Investigation of electronic properties using quantum Hall effect measurements under magnetic fields.
• Analysis of Landau level reordering and degeneracy changes.

Main Results:

• Observation of pure valley-Zeeman spin-orbit coupling in encapsulated graphene.
• Symmetry-enforced reordering of Landau levels due to competition between valley-Zeeman and cyclotron energies.
• Transition from symmetry-broken to fourfold degenerate states in the quantum Hall effect, exhibiting integer and half-integer sequences.
• Demonstration of complete quenching of proximity SOC by tuning the encapsulation geometry.

Conclusions:

• Twisted WSe₂ encapsulation provides a platform for engineering pure valley-Zeeman SOC in graphene.
• The observed Landau level reordering offers insights into quantum interference and symmetry effects.
• Tunable proximity SOC opens avenues for designing novel electronic and spintronic devices.