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The scaling behavior of the charging energy of a quantum dot with asymmetrically adjusted tunnel barriers is measured through the amplitude of the Coulomb oscillations in the thermovoltage. For weak coupling between the dot and the reservoirs, we observe a linear scaling of the effective charging energy when the transmission probability of one tunnel barrier is increased. At higher transmission probabilities, we find a deviation from the linear scaling and a crossover to a constant value. This behavior is caused by the chaotic nature of the electron trajectories within the dot.

We present measurements of the magneto-thermopower fluctuations of a gate-defined, chaotic quantum dot in a (Al,Ga)As-semiconductor heterostructure. Current-heating techniques were employed to build up the necessary temperature difference across the quantum dot for the thermopower measurement. A statistical ensemble is generated by registering the magnetic-field and gate-voltage dependence for a number of slightly different dot sizes. The experimental results are in good agreement with the predicted non-gaussian distribution of the Random Matrix Theory. To our knowledge these are the first transport experiments that directly yield the non-gaussian distribution which are an unambiguous sign for the occurence of chaos.

We demonstrate experimentally and by Monte Carlo simulation that the negative dips which occur at low magnetic fields on both sides of the main signal in nonlocal electron-beam measurements in semiconductor nanostructures result from electrons following classical rebound trajectories. We propose an alternative measurement geometry that eliminates these effects.

This paper reviews recent studies of mesoscopic fluctuations in transport through ballistic quantum dots, emphasizing differences between conduction through open dots and tunneling through nearly isolated dots. Both the open dots and the tunnel-contacted dots show random, repeatable conductance fluctuations with universal statistical proper-ties that are accurately characterized by a variety of theoretical models including random matrix theory, semiclassical methods and nonlinear sigma model calculations. We apply these results in open dots to extract the dephasing rate of electrons within the dot. In the tunneling regime, electron interaction dominates transport since the tunneling of a single electron onto a small dot may be sufficiently energetically costly (due to the small capacitance) that conduction is suppressed altogether. How interactions combine with quantum interference are best seen in this regime., 15 pages, 11 figures, PDF 2.1 format, to appear in "Chaos, Solitons & Fractals"

We report measurements of mesoscopic fluctuations of Coulomb blockade peaks in a shapedeformable GaAs quantum dot. Distributions of peak heights agree with predicted universal functions for both zero and nonzero magnetic fields. Parametric fluctuations of peak height and position, measured using a two-dimensional sweep over gate voltage and magnetic field, yield autocorrelations of height fluctuations consistent with a predicted Lorentzian-squared form for the unitary ensemble. We discuss the dependence of the correlation field on temperature and coupling to the leads as the dot is opened.