Non-Gaussian distribution of nearest-neighbour Coulomb peak spacings in metallic single-electron transistors

The distribution of nearest-neighbour spacings of Coulomb blockade oscillat ion peaks in normal conducting aluminum single-electron transistors is foun d to be non-Gaussian. A pronounced tail to reduced spacings is observed, wh ich we attribute to impurity-specific parametric charge rearrangements clos e to the transistor. Our observation may explain the absence of a Wigner-Dy son distribution in the experimental nearest-neighbour spacing distribution s in semiconductor quantum dots.