Poisson and Wigner-Dyson distributions of conductance fluctuations in quantum cavities

We investigate the statistical properties of conductance fluctuations in quantum cavities when the underlying classical dynamics is either regular or chaotic. Regardless of the dynamics, the correlation magnetic field of the conductance fluctuations in ballistic cavities increases linearly with the lead width, in contrast to its independence on the lead width in diffusive conductors. The linear increase is a consequence of electrons staying shorter in the cavity for wider leads. The probability distributions of the magnetic field and energy spacings between the nearest-neighbor peaks and dips in the conductance are found to be described by the Poisson distribution for regular quantum cavities and by the Wigner-Dyson distribution for chaotic quantum cavities. We also examine the influence of dephasing in the quantum cavities on the statistical behavior.