Quenching of Infrared-Active Optical Phonons in Nanolayers of Crystalline Materials by Graphene Surface Plasmons

Optical phonons are fundamental excitations in many solid-state materials and have crucial influences on numerous material properties. Therefore, achieving extrinsic control of optical phonon properties, such as the phonon frequency, lifetime and population, may lead to new ways of tailoring various material properties relevant to key technological applications. Here, we experimentally demonstrate that infrared-active optical phonons in thin (tens of nm) layers of crystalline materials such as III-V semiconductors can be significantly quenched by a monolayer graphene. The optical phonon quenching effect is attributed to the ultrafast decay of optical phonons into resonant graphene surface plasmons at a rate which is significantly higher than the intrinsic decay rate of optical phonons due to lattice anharmonicity. Our results point to a new approach to engineering optical phonon properties and potentially other related material properties. Such an approach can be applied to a wide range of materials with infrared-active optical phonons.