Quantum chaos in GaAs/AlxGa1-xAs microstructures

We review clear signatures of "quantum chaos" observable in both open and c losed systems realized in GaAs/AlxGa1-xAs microstructures. In open ballisti c billiards where scattering dynamics determine the characteristics of quan tum transport, we find a striking difference in the shape of the negative m agneto-resistance peak for transport through chaotic, stadium cavities-Lore ntzian line shape, versus non-chaotic, circle cavities-unusual triangular l ine shape. In a nearly closed system of individual quantum dot single-elect ron-transistors, the distribution of the height of Coulomb blockade conduct ance peaks is strongly non-Gaussian and sensitive to the absence or presenc e of a magnetic field. Even though our findings are in substantial agreemen t with the prediction of Random Matrix Theory, there exist evidence that de viations can occur due to the effect of electron-electron interaction, Last ly, we briefly summarize recent observations of pairing effect in ultra-sma ll quantum dots associated with the spin degree of freedom.