Universal slow plasmons and giant field enhancement in atomically thin quasi-twodimensional metals

Nature Communications 11,1013, (2020)

Universal slow plasmons and giant field enhancement in atomically thin quasi-twodimensional metals

Felipe H. da Jornada,Lede Xian,Angel Rubio, Steven G. Louie

Plasmons depend strongly on dimensionality: while plasmons in three-dimensional systems start with finite energy at wavevector q = 0, plasmons in traditional two-dimensional (2D) electron gas disperse as ωp∼√q. However, besides graphene, plasmons in real, atomically thin quasi-2D materials were heretofore not well understood. Here we show that the plasmons in real quasi-2D metals are qualitatively different, being virtually dispersionless for wavevectors of typical experimental interest. This stems from a broken continuous translational symmetry which leads to interband screening; so, dispersionless plasmons are a universal intrinsic phenomenon in quasi-2D metals. Moreover, our ab initio calculations reveal that plasmons of monolayer metallic transition metal dichalcogenides are tunable, long lived,able to sustain field intensity enhancement exceeding 107, and localizable in real space(within ~20 nm) with little spreading over practical measurement time. This opens the possibility of tracking plasmon wave packets in real time for novel imaging techniques in atomically thin materials.

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This work was supported by the Center for Computational Study of Excited-State Phenomena in Energy Materials (C2SEPEM) funded by the U.S. Department of Energy,Office of Basic Energy Sciences under Contract No. DE-AC02-05CH11231 at LawrenceBerkeley National Laboratory, as part of the Computational Materials Sciences Program,which provided for theory development, code implementation, and calculations. Computational resources were provided by the National Energy Research Scientific Computing Center (NERSC), which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by the National Science Foundation under Grant No. ACI-1053575. We acknowledge financial support from the European Research Council (ERC-2015-AdG-694097). The Flatiron Institute is a division of the Simons Foundation. The authors thank D. Basov, D.Y. Qiu, and H.S. Sen for helpful discussions.

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