Weak localization and chaos in ballistic quantum dots

Ballistic fluctuations due to coherent mode mixing dominate magnetotransport in the dot at milli Kelvin temperatures. As the temperature is increased and Ohmic behavior is established in the dot, the shape of the weak localization (WL) peak follows the linear dependence predicted by the semi-classical theory for regular electron billiards. This temperature sets a limit above which these predictions can be observed at a single device. The shape of the WL peak is quite robust to the rounding of the QPC openings, whereas a relatively small rounding of corners inside the dot (which is thought to be caused by varying of the the gate voltage) is sufficient to destroy regular motion of the electrons in the nominally square dot. This may explain a transition from the linear to the Lorentzian dependence of the WL peak (the latter is characteristic for chaotic billiards in the semiclassical picture) which was detected in the recent experiments. The probability density distribution inside the dot is visualized and analyzed.