Fig. 2: Near-field infrared imaging of hybrid plasmon-phonon modes.
From: Surface plasmons induce topological transition in graphene/α-MoO3 heterostructures
a, b Near-field amplitude image of a WOx/graphene/α-MoO3 heterostructure with ~0.60 eV hole doping in graphene from charge transfer with the WOx monolayer. The experimental polariton wavefront displays the characteristic elliptical shape from finite-difference time-domain simulations shown in panel b to the right. c Near-field amplitude image and, d simulated wavefront of a defect in bare α-MoO3 launching hyperbolic wavefronts—in contrast to the closed wavefront in a where [001] modes appear after the topological transition caused by plasmon-phonon hybridization. e Line profiles extracted along the white dashed lines in a showing both [100] and [001] modes. Black dashed lines align the first peaks. f [100] Line profiles extracted from either side of the WOx edge (white dashed line) in g. Wavelengths of [100] modes increase as a result of plasmon-phonon hybridization upon doping.
