Quantum chaos in microstructures

We report distinct signatures of ‘quantum chaos’ in both open and closed systems. Quantum chaos refers to the quantum signature of systems which classically exhibit chaotic dynamics. In the open case, we measure the line shape of the negative magneto-resistance peak in ballistic cavities fabricated on very high quality heterostructures. We find a striking difference in the line shape for chaotic, stadium cavities versus non-chaotic, circle cavities: Lorentzian versus triangular. In the case of closed systems, we study the distribution of Coulomb blockade conductance peak heights in individual quantum dots. We find a strongly non-Gaussian distribution and a significant difference between the zero and non-zero magnetic fields. While the zero magnetic field distribution is related to the well-known Porter-Thomas distribution of resonance widths in the scattering of neutrons from nuclei, the non-zero magnetic field distribution is completely new and previously unobserved.