Nanoscale light trapping in graphene/h-BN by sound waves (Vol. 49 No.4)

SAW-driven generation of polaritons in graphene/h-BN on a piezoelectric; Insets: Electric field profile for surface and hyperbolic plasmon-phonon polaritons (SPPP and HPPP)

Graphene plasmonics is a rapidly emerging field exploiting the extreme light confinement provided by the 2D nature of graphene that results in enhanced light-matter interaction. However, a large momentum mismatch needs to be overcome by a photon to couple with a plasmon into a plasmon polariton. In this work, the authors have demonstrated a unique way for exciting polaritons in graphene/h-BN systems on a piezoelectric material by using a surface acoustic wave (SAW) generated by an integrated transducer. The SAW acts as a virtual diffraction grating providing the extra momentum needed to generate propagating polaritons using a simple laser. h-BN is widely used as an ideal substrate for graphene providing it with very high mobility. Moreover, h-BN is a natural hyperbolic insulator (i.e. the dielectric function has opposite sign in the two reststrahlen bands), where graphene plasmons couple strongly to both surface and hyperbolic (waveguided) phonons in h-BN, leading to hybridized surface and hyperbolic plasmon-phonon polaritons. These results pave the way for engineering SAW-driven graphene/h-BN plasmonic devices and metamaterials covering the mid-IR to THz range.

R. Fandan, J. Pedrós, J. Schiefele, A. Boscá, J. Martínez and F. Calle, Acoustically-driven surface and hyperbolic plasmon-phonon polaritons in graphene/h-BN heterostructures on piezoelectric substrates, J. Phys. D: Appl. Phys. 51, 204004 (2018)