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Plasmon modes of spatially separated double-layer graphene

2009; American Physical Society; Volume: 80; Issue: 20 Linguagem: Inglês

10.1103/physrevb.80.205405

1550-235X

E. H. Hwang, S. Das Sarma,

Topological Materials and Phenomena

We derive the plasmon dispersion in doped double-layer graphene (DLG), made of two parallel graphene monolayers with carrier densities ${n}_{1}$ and ${n}_{2}$, respectively, and an interlayer separation of $d$. The linear chiral gapless single-particle energy dispersion of graphene leads to DLG plasmon properties with several unexpected experimentally observable characteristic features such as a nontrivial influence of an undoped $({n}_{2}=0)$ layer on the DLG plasmon dispersion and a strange influence of the second layer even in the weak-coupling $d\ensuremath{\rightarrow}\ensuremath{\infty}$ limit. At long wavelengths $(q\ensuremath{\rightarrow}0)$, the density dependence of the plasma frequencies is different from the usual two-dimensional (2D) electron system with quadratic energy dispersion. Our predicted DLG plasmon properties clearly distinguish graphene from the extensively studied usual parabolic 2D electron systems.