Surface plasmons induce topological transition in graphene/α-MoO₃ heterostructures

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanophotonics

Background:

• Hyperbolic polaritons in van der Waals materials exhibit unique light-matter interactions due to opposite signs of permittivity along principal axes.
• Topological transitions of these polaritons, from open hyperbolas to closed curves, alter physical properties and are crucial for integrated technologies.
• Electronically tunable topological transitions remain undemonstrated, limiting their application in advanced devices.

Purpose of the Study:

• To demonstrate a doping-induced topological transition in hyperbolic polaritons.
• To investigate plasmon-phonon hybridization in graphene/α-MoO3 heterostructures for tunable polariton modes.
• To explore the potential of these heterostructures for novel nanophotonic and quantum devices.

Main Methods:

• Fabrication of graphene/α-MoO3 heterostructures.
• Utilized scanning near-field optical microscopy (SNOM) to image and characterize hybrid polaritons.
• Investigated doping effects to induce topological transitions.

Main Results:

• Successfully demonstrated a doping-induced topological transition in hyperbolic polaritons within graphene/α-MoO3 heterostructures.
• Characterized hybrid polariton modes, showing tunability from surface waves to bulk waveguide modes.
• Observed an exceptional point resulting from anisotropic plasmon-phonon coupling, enabling mode transition.

Conclusions:

• Graphene/α-MoO3 heterostructures enable electronically tunable topological transitions in hyperbolic polaritons via plasmon-phonon hybridization.
• The demonstrated tunability and control over polariton modes open avenues for dynamical topological transitions and directional coupling.
• These findings inspire the development of new nanophotonic and quantum devices with unprecedented functionalities.