Ultrafast nonlinear optical response of the quantum Hall system

The quantum Hall effects (QH) arise in a cold 2D electron gas (2DEG) subject to a perpendicular magnetic field. They result from Coulomb correlations among the 2DEG that populates the highly degenerate Landau level (LL) states. Here we study the coherent nonlinear optical response of the QH system. Recent ultrafast four-wave-mixing (FWM) experiments indicate an important role of the magnetoplasmon (MP) collective excitations of this incompressible fluid.