Energy-averaged weak localization in chaotic microcavities

We have fabricated ballistic cavities from a two-dimensional GaAs electron gas in which the Fermi energy can be varied independent of cavity shape. For each cavity, we have measured the magnetoconductance $G\left(B\right)\mathrm{}$ of many individual members of an ensemble, with each member labeled by its Fermi energy. We find that $G\left(B\right)\mathrm{}$ of a single ensemble member does not always display the minimum at $B=0\mathrm{}$ which is the signature of weak localization. By averaging over our ensemble, we have obtained the energy-averaged weak-localization effect for each cavity shape. The average result does display the expected minimum at $B=0\mathrm{}$. We compare our results with recent analytical theories and numerical simulations of weak localization in cavities with chaotic classical scattering and find good quantitative agreement.