Towards quantum plasmonics: excitation of 2D plasmons via coupling with quantum dots and 2D materials

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Towards quantum plasmonics: excitation of 2D plasmons via coupling with quantum dots and 2D materialsThe mutual interplay between photons and plasmon quasiparticles is used in the field of plasmonics to propagate information across surfaces, confine and guide light and use surface plasmon polaritons (SPP) for quantum computing. Collective excitations in low dimensional electron gases, so-called sheet plasmons, provide tunable energies and wavelengths from the THz to the optical regime on a truly nanometer scale, respectively, and are therefore promising. However, compared to the well-established field of SPPs, new concepts are mandatory in order to couple light and to excite sheet-plasmon-polariton quasiparticles.In this proposal, we will study the interaction of sheet plasmons of low dimensional electron gases coupled to other oscillators. Among others, metallic and semiconducting quantum dots (QDs), as well as 2D materials (TMDCs, molecular layers) are used to study plasmon-plasmon and plasmon-exciton excitations on a true nanometer scale. By means of epitaxial graphene, providing a quasi-perfect 2D electron gas system (2DEG), the different interaction schemes are studied in detail by both electron- and photon-assisted excitations. Moreover, the chemical flexibility of epitaxial graphene enable us to use various functionalization schemes, e.g., adsorption of QDs from the liquid phase, adsorption of molecules in vacuum, growth of 2D materials and intercalation of metals. Using high resolution electron energy loss spectroscopy and scanning near-field optical microscopy the coupling and amplification of plasmons is studied in reciprocal and real space. The experiments are supplemented by (multi-tip) scanning tunneling microscopy to control the atomic scale, charge transfer and perform opto-electronic energy conversion experiments on the nanoscale.