Electronic ground state properties of Coulomb blockaded quantum dots

Conductance through quantum dots at low temperature exhibits random but repeatable fluctuations arising from quantum interference of electrons. The observed fluctuations follow universal statistics arising from the underlying universality of quantum chaos. Random matrix theory (RMT) has provided an accurate description of the observed universal conductance fluctuations (UCF) in “open” quantum dots (device conductance ≥e 2/h). The focus of this thesis is to search for and decipher the underlying origin of similar universal properties in “closed” quantum dots (device conductance ≤e2/ h). A series of experiments is presented on electronic ground state properties measured via conductance measurements in Coulomb blockaded quantum dots. The statistics of Coulomb blockade (CB) peak heights with zero and non-zero magnetic field measured in various devices agree qualitatively with predictions from Random Matrix Theory (RMT). The standard deviation of the peak height fluctuations for non-zero magnetic field is lower than predicted by RMT; the temperature dependence of the standard deviation of the peak height for non-zero magnetic field is also measured. The second experiment summarizes the statistics of CB peak spacings. The peak spacing distribution width is observed to be on the order of the single particle level spacing, Δ, for both zero and non-zero magnetic field. The ratio of the zero field peak spacing distribution width to the non-zero field peak spacing distribution width is ∼1.2; this is good agreement with predictions from spin-resolved RMT predictions. The standard deviation of the non-zero magnetic field peak spacing distribution width shows a T−1/2 dependence in agreement with a thermal averaging model. The final experiment summarizes the measurement of the peak height correlation length versus temperature for various quantum dots. The peak height correlation length versus temperature saturates in small quantum dots, suggesting spectral scrambling after adding a small number of electrons. Larger devices show saturation to a higher value suggesting that the larger devices are less prone to spectral scrambling. Enhanced correlation, arising possibly from pairs of CB peaks with similar peak heights, is observed in all dots at low temperature.