Imaging and Simulation of Surface Plasmon Polaritons on Layered 2D MXenes

Two-dimensional transition metal carbides and nitrides, commonly known as MXenes, are a novel class of 2D materials with high free carrier densities, making them highly attractive candidates for plasmonic 2D materials. In this study, we use multiphoton photoemission electron microscopy (nP-PEEM) to directly image the plasmonic near fields of multilayers of the prototypical MXene, Ti3C2Tx, with mixed surface terminations (Tx = F, O, and OH). Photon-energy dependent nP-PEEM reveals a dispersive surface plasmon polariton between 1.4 eV and 1.9 eV on MXene flakes thicker than 30 nm and waveguide modes above 1.9 eV. Combining experiments with finite difference time domain (FDTD) simulations, we reveal the emergence of a visible surface plasmon polariton in MXenes, opening avenues for exploration in polaritonic phenomena in MXenes in the visible portion of the electromagnetic spectrum.