Phase breaking in ballistic quantum dots: A correlation field analysis

We use a novel technique to determine the phase breaking time τ_φ of electrons in ballistic quantum dots, from the aperiodic fluctuations observed in their low-temperature magnetoconductance. At temperatures below 100 mK, roughly similar values of τ_φ are obtained in both sizes of dot studied, suggesting a strong materials-related influence on τ_φ. Analysing the temperature-dependent characteristics of the fluctuations, τ_φ is found to scale roughly inversely with temperature close to 1 K, reminiscent of electron-electron scattering in two-dimensional disordered systems. At much lower temperatures, however, a saturation in τ_φ is observed, and is thought to result from a transition from two-to zero-dimensional transport, which occurs as the discrete level structure of the dot becomes resolved.