The low temperature magnetoconductance of a large array of quantum coherent loops exhibits Altshuler-Aronov-Spivak oscillations with a periodicity corresponding to $1/2$ flux quantum per loop. We show that the measurement of the harmonics content provides an accurate way to determine the electron phase-coherence length $L_{\phi }$ in units of the lattice length with no adjustable parameters. We use this method to determine $L_{\phi }$ in a square network realized from a 2D electron gas in a $\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{l}\mathrm{A}\mathrm{s}$ heterojunction, with only a few conducting channels. The temperature dependence follows a power law $T^{-1/3}$ from 1.3 K to 25 mK with no saturation, as expected for 1D diffusive electronic motion and electron-electron scattering as the main decoherence mechanism.

• Received 23 February 2004

DOI:https://doi.org/10.1103/PhysRevLett.93.246804