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

TL;DR

This paper presents a method to directly measure the electron phase coherence length in a GaAs/GaAlAs quantum network using magnetoconductance oscillations, revealing a temperature dependence consistent with 1D diffusive electron behavior.

Contribution

The study introduces a parameter-free technique to determine the phase coherence length from harmonic analysis of magnetoconductance oscillations in a quantum network.

Findings

Phase coherence length follows a power law T^{-1/3} from 1.3 K to 25 mK.

No saturation of coherence length observed at low temperatures.

Method applicable to 2DEG systems in heterojunctions.

Abstract

The low temperature magnetoconductance of a large array of quantum coherentloops exhibits Altshuler-Aronov-Spivak oscillations which periodicitycorresponds to 1/2 flux quantum per loop.We show that the measurement of the harmonics content in a square networkprovides an accurate way to determine the electron phase coherence length$L\_{\phi}$ in units of the lattice length without any adjustableparameters.We use this method to determine $L\_{\phi}$ in a network realised from a 2Delectron gas (2DEG) in a GaAS/GaAlAs heterojunction. The temperaturedependence follows a power law $T^{-1/3}$ from 1.3 K to 25 mK with nosaturation, as expected for 1D diffusive electronic motion andelectron-electron scattering as the main decoherence mechanism.