Direct measurement of the phase-coherence length in a GaAs/GaAlAs square network

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 GaAs/GaAlAs 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.