Transverse electric graphene plasmons are generally weakly confined in the direction perpendicular to the graphene plane. They are featured by a skin depth δ, namely the penetration depth of their evanescent fields into the surrounding environment, much larger than the wavelength λ in free space (e.g., δ > 10λ). The weak spatial confinement of transverse electric graphene plasmons is now the key drawback that limits their practical applications. Here we report the skin depth of TE graphene plasmons can be largely decreased down to the subwavelength scale (e.g., δ < λ/10) in negative refractive-index environments. The underlying mechanism originates from the different existence conditions for TE graphene plasmons in negative and positive refractive-index environments. To be specific, their existence in negative (positive) refractive-index environments requires Im(σ_s) > 0 (Im(σ_s) < 0) and lies in the frequency range of ħω/μ_c < 1.667 (ħω/μ_c > 1.667), where σ_s and μ_c are the surface conductivity and chemical potential of monolayer graphene, respectively.

横向石墨烯等离子体激元通常在垂直于石墨烯平面的方向上被弱地限制。它们的特征是皮肤深度δ，即它们的e逝场进入周围环境的穿透深度，比自由空间中的波长λ大得多（例如δ  > 10λ）。现在，横向电石墨烯等离子体激元的空间限制较弱，这是限制其实际应用的主要缺点。在这里，我们报道TE石墨烯等离子体激元的趋肤深度可以大大降低至亚波长范围（例如，δ  <  λ/ 10）在负折射率环境中。潜在的机理源自在负和正折射率环境中TE石墨烯等离子体激元的不同存在条件。具体而言，它们在负（正）存在折射率的环境需要IM（σ_小号）> 0（IM（σ_小号）<0）和在于频率范围Hω / μ _ç  <1.667（Hω / μ _Ç  > 1.667），其中σ_小号和μ _ç分别是表面导电性和单层石墨烯的化学势。