Optically Induced Circular Currents and Giant Inverse Faraday Effect in 2D Electron Liquid for Tunable Absorption of THz radiation

S.O. Potashin, V. Yu. Kachorovskii, M.S. Shur
Rensselaer Polytechnic Institute,
United States

Keywords: terahertz technology, plasmonics, inverse Faraday effect, tunable absorber


We show that a small conducting nanosphere or a nanoring embedded into or placed in the vicinity of the two-dimensional electron fluid (2DEL) and subjected to a circularly polarized electromagnetic radiation induces “twisted'' plasmonic oscillations in the adjacent 2DEL. The oscillations are rectified due to the hydrodynamic nonlinearities leading to the helicity sensitive circular dc current and to a magnetic moment. This hydrodynamic Inverse Faraday Effect (HIFE) can be observed at room temperature in different materials including silicon. The HIFE is dramatically enhanced by using a periodic array of the nanospheres forming a resonant plasmonic coupler. Such a coupler exposed to a circularly polarized wave converts the entire 2DEL into a vortex state. Hence, the twisted plasmonic modes support resonant plasmonic-enhanced gate-tunable optical magnetization. Due to the interference of the plasmonic and Drude contributions, the resonances have an asymmetric Fano-like shape. These resonances present a signature of the 2DEL properties not affected by contacts and interconnects and, therefore, providing the most accurate and complete information about the 2DEL properties. In particular, the width of the resonances encodes direct information about the momentum relaxation time and viscosity of the 2DEL. For typical parameters of 2DEL, the vortex state is achieved at THz frequencies and this system could enable THz detectors, mixers, frequency multipliers, and resonant tunable absorbers.