TEMPERATURE-DEPENDENCE OF PHASE BREAKING IN BALLISTIC QUANTUM DOTS

Ballistic conductance fluctuations are measured in a zero-dimensional (0D) GaAs quantum dot and are used to measure the phase coherence life time tau(phi)(T) based on a semiclassical ''extra lead'' model of phas e breaking. Above 300 mK, the measured tau(phi) decreases as a power l aw, tau(phi)(T) = a(T [K])-zeta, with zeta similar to 1.2 and a simila r to 3.5 X 10(-11) s, and appears to saturate below this temperature. Variance of fluctuations increases from zero with dot conductance for few conducting channels in the leads, then saturates once several chan nels are open. Above 150 mK, variance decreases with temperature as a power law with an exponent between -1.2 and -1.6 depending on [g].