Large terahertz electric dipole of a single graphene quantum dot

Abstract

Graphene has recently emerged as an important material for optoelectronic applications owing to its unique properties. Here, we show that graphene is also appealing for the development of THz quantum optics when used for quantum dots. In particular, we demonstrate a large electric dipole of length d≈230 nm in a single graphene quantum dot, corresponding to an amplitude of ≈10μeV for the THz field. This estimate is done using transport measurements under coherent THz illumination and the well-established photon-assisted tunneling phenomenon for a spectral range larger than 100 GHz. Such large THz electric dipole for a quantum system that involves single-electron tunneling is suitable for future quantum optics experiments using graphene quantum dots strongly coupled to a THz cavity.