Spectral characteristics of conductance fluctuations in ballistic quantum dots

We report on detailed studies of the low-field magnetoconductance fluctuations observed in ballistic GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum dots. The main finding of our study is that the temperature-dependent scaling of the fluctuations is very different from that in disordered systems. In particular, the amplitude of the fluctuations decays exponentially with increasing temperature while the correlation field remains unaltered. We suggest that these results are consistent with the scattering of electrons via geometrical features, and so demonstrate the different nature of electron interference in disordered and ballistic systems. Finally, we discuss our results in relation to recent theoretical predictions for ballistic dots with chaotic geometries, in order to obtain information on the distribution of electronic trajectories in the square dots we study.