Topological edge modes in non-Hermitian plasmonic waveguide arrays

Area of Science:

• Condensed matter physics
• Photonics
• Materials science

Background:

• Topological edge modes in non-Hermitian systems are crucial for robust light transport.
• Graphene's tunable properties offer potential for novel photonic devices.
• Parity-time (PT) symmetry breaking is key in non-Hermitian photonics.

Purpose of the Study:

• To investigate topological edge modes of surface plasmon polaritons (SPPs) in graphene.
• To explore the role of gain and loss in controlling these modes.
• To demonstrate deep-subwavelength light confinement and control.

Main Methods:

• Utilizing graphene pair arrays with alternating gain and loss.
• Analyzing the emergence of topological edge modes at the interface of distinct arrays.
• Investigating the influence of parity-time (PT) symmetry breaking.
• Tuning graphene's chemical potential to control beam diffraction.

Main Results:

• Topological edge modes were observed in the non-Hermitian graphene system.
• Gain and loss were shown to control propagation loss and field distributions.
• Beam diffraction was successfully steered by tuning the chemical potential.
• Deep-subwavelength confinement of SPPs to ~λ/70 was achieved.
• Modes were also realized in lossy graphene waveguides without gain.

Conclusions:

• The study demonstrates a promising approach for robust light transport.
• The findings pave the way for optical switches on a deep-subwavelength scale.
• Non-Hermitian graphene systems offer versatile control over photonic properties.