Critical magnetodynamics in quantum dot arrays

Abstract

Arrays of coupled quantum dots are analysed by employing the randomly jumping interacting moments model including quantum fluctuations due to the discrete level structure, ferromagnetic inter-dot coupling and disorder. The respective magnetic state equation and phase diagram are found to indicate an existence of spinodal regions and critical points. In vicinity of such points magnetic induction shows jerky behaviour displayed as erratic discontinuities associated with avalanches of the dot magnetization. The model predicts some universal scaling properties for magnetic noise. On the basis of such properties we suggest and test model-independent analytical tools employed in order to specify, quantify and analyse the system with respect to the observed magnetic structure. Some specific features for arrays of dots with singlet-triplet transitions are discussed.