# Long-lived domain wall plasmons in gapped bilayer graphene

## TL;DR

This paper predicts the existence of long-lived, tunable plasmons along topological domain walls in gapped bilayer graphene, offering a new platform for low-dissipation plasmonic applications.

## Contribution

It introduces the concept of domain wall plasmons in bilayer graphene, highlighting their exceptional lifetimes and unique properties distinct from bulk plasmons.

## Key findings

- Domain wall plasmons can propagate at zero bulk density.
- These plasmons have lifetimes up to a few picoseconds at room temperature.
- They exhibit tunable frequencies and sub-wavelength confinement.

## Abstract

Topological domain walls in dual-gated gapped bilayer graphene host edge states that are gate- tunable and valley polarized. Here we predict that plasmonic collective modes can propagate along these topological domain walls even at zero bulk density, and possess a markedly different character from that of bulk plasmons. Strikingly, domain wall plasmons are extremely long-lived, with plasmon lifetimes that can be orders of magnitude larger than the transport scattering time in the bulk. While most pronounced at low temperatures, long domain wall plasmon lifetimes persist even at room temperature with values up to a few picoseconds. Domain wall plasmons possess a rich phenomenology including a wide range of frequencies (up to the mid-infrared), tunable sub-wavelength electro-magnetic confinement lengths, as well as a valley polarization for forward/backward propagating modes. Its unusual features render them a new tool for realizing low-dissipation plasmonics that transcend the restrictions of the bulk.