Nonlocal dynamic response and level crossings in quantum-dot structures

Very small quantum-dot structures containing 210 to 25 electrons per dot have been prepared starting from modulation-doped AlGaAs/GaAs heterostructures. The far-infrared response consists of a set of resonances which split, in a magnetic field B, into branches with negative and positive B dispersion. The intersection of these resonances, in classical analogy edge magnetoplasmons, leads to an anticrossing of the dispersions. This resonant coupling is induced by nonlocal interaction which becomes important at small dimensions.