Quantum Coherence at Low Temperatures in Mesoscopic Systems: Effect of Disorder

TL;DR

This study investigates how disorder affects quantum coherence in mesoscopic GaAs/AlGaAs systems, revealing different behaviors of phase coherence time across diffusive, semi-ballistic, and localized regimes.

Contribution

It introduces an ion implantation technique to tune disorder in 2D electron gases and explores phase coherence behavior across various transport regimes.

Findings

Phase coherence time follows a power law in the diffusive regime.

In the semi-ballistic regime, coherence time becomes independent of diffusion.

Localized regime shows diverging coherence time with decreasing temperature.

Abstract

We study the disorder dependence of the phase coherence time of quasi one-dimensional wires and two-dimensional (2D) Hall bars fabricated from a high mobility GaAs/AlGaAs heterostructure. Using an original ion implantation technique, we can tune the intrinsic disorder felt by the 2D electron gas and continuously vary the system from the semi-ballistic regime to the localized one. In the diffusive regime, the phase coherence time follows a power law as a function of diffusion coefficient as expected in the Fermi liquid theory, without any sign of low temperature saturation. Surprisingly, in the semi-ballistic regime, it becomes independent of the diffusion coefficient. In the strongly localized regime we find a diverging phase coherence time with decreasing temperature, however, with a smaller exponent compared to the weakly localized regime.