Cross-correlated noise measurements are performed in etched AlxGa1-xAs/GaAs based quantum rings in equilibrium at bath temperature of Tbath=4.2 K. The measured white noise exceeds the thermal (Johnson-Nyquist) noise expected from the measured electron temperature Te and the electrical resistance R. This excess part of the white noise decreases as Tbath increases and vanishes for Tbath≥12 K. Excess noise is neither observed if one arm of a quantum ring is depleted of electrons nor in 1D-constrictions that have a length and width comparable to the quantum rings. A model is presented that suggests that the excess noise originates from the correlation of noise sources, mediated by phase-coherent propagation of electrons.
@article{arxiv.1912.04397,
title = {Excess noise in Al${}_\text{x}$Ga${}_\text{1-x}$As/GaAs based quantum rings},
author = {Christian Riha and Sven S. Buchholz and Olivio Chiatti and Andreas D. Wieck and Dirk Reuter and Saskia F. Fischer},
journal= {arXiv preprint arXiv:1912.04397},
year = {2019}
}