STATISTICS OF COULOMB-BLOCKADE PEAK SPACINGS

Distributions of Coulomb blockade peak spacings are reported for large ensembles of both unbroken (magnetic field B = 0) and broken (B not e qual 0) time-reversal symmetry in GaAs quantum dots. Both distribution s are symmetric and roughly Gaussian with a width of similar to 2%-6% of the average spacing, with broad, non-Gaussian tails. The distributi on is systematically wider at B = 0 by a factor of similar to 1.2 +/- 0.1. No even-odd spacing correlations or bimodal structure in the spac ing distribution is found, suggesting an absence of spin degeneracy. T here is no observed correlation between peak spacing and peak height.