Coulomb Blockade Peak Spacing Fluctuations in Deformable Quantum Dots: A Further Test of Random Matrix Theory

Abstract

We propose a mechanism to explain the fluctuations of the ground state energy in quantum dots in the Coulomb blockade regime. Employing random matrix theory we show that shape deformations may change the adjacent peak spacing distribution from Wigner-Dyson to nearly Gaussian even in the absence of charging energy fluctuations. The distribution is determined by the average number of anticrossings between successive conductance peaks and the presence or absence of a magnetic field. Our mechanism is tested in a dynamical model whose classical dynamics is chaotic. The results are in good agreement with experiments and apply to spin resolved or spin degenerate states. [S0031-9007(98)06645-9] PACS numbers: 73.23.Hk, 05.45. + b Most phenomena in mesoscopic electronic transport are well understood invoking the picture of a single quantum particle moving coherently in a disordered or complex potential. In the case of semiconductor quantum dots, the complexity of the background or confining potential is manifest in the chaotic nature of the underlying electronic classical dynamics. A large amount of literature [1] indicates that the statistical properties of the spectra of chaotic systems are successfully modeled by random matrix theory (RMT) [2]. When applied to transport in open ballistic quantum dots of irregular shape, this theory predicts a strong universal behavior for the statistical fluctuations of the conductance, similar to that found in disordered systems [3]. Over the last few years, several experiments confirmed this behavior, making open electronic cavities one of the paradigms of quantum chaos [4,5].