Optical N-plasmon: Topological hydrodynamic excitations in Graphene from repulsive Hall viscosity

TL;DR

This paper introduces the concept of optical N-plasmons in graphene, revealing topologically protected edge excitations driven by repulsive Hall viscosity, with potential applications in topological photonic devices.

Contribution

It proposes the existence of optical N-plasmons as topologically protected edge states in graphene, driven by repulsive Hall viscosity, and demonstrates their unique properties and tunability.

Findings

Optical N-plasmons exhibit distinct dispersion and edge profiles from trivial plasmons.

The work demonstrates a topological hydrodynamic circulator based on optical N-plasmons.

Optical N-plasmons can be tuned via dielectric environment without losing topological protection.

Abstract

Edge states occurring in Chern and quantum spin-Hall phases are signatures of the topological electronic band structure in two-dimensional (2D) materials. Recently, a new topological electromagnetic phase of graphene characterized by the optical N-invariant has been proposed. Optical N-invariant arises from repulsive Hall viscosity in hydrodynamic many-body electron systems, fundamentally different from the Chern and Z2 invariants. In this paper, we introduce the topologically protected edge excitation -- optical N-plasmon of interacting many-body electron systems in the topological optical N-phase. These optical N-plasmons are signatures of the topological plasmonic band structure in 2D materials. We demonstrate that optical N-plasmons exhibit fundamentally different dispersion relations, stability, and edge profiles from the topologically trivial edge magneto plasmons. Based on the optical N-plasmon, we design an ultra sub-wavelength broadband topological hydrodynamic circulator, which is a chiral quantum radio-frequency circuit component crucial for information routing and interfacing quantum-classical computing systems. Furthermore, we reveal that optical N-plasmons can be effectively tuned by the neighboring dielectric environment without breaking the topological properties. Our work provides a smoking gun signature of repulsive Hall viscosity and opens practical applications of topological electromagnetic phases of two-dimensional materials.