Coulomb blockade thermometry beyond the universal regime

TL;DR

This paper extends Coulomb blockade thermometry beyond the universal regime by numerically analyzing large junction arrays, showing improved accuracy at very low temperatures despite charge offset effects.

Contribution

It demonstrates that large junction arrays can maintain primary thermometry capabilities even with device parameter variations and charge offsets.

Findings

Simulations agree with experimental conductance data at submillikelvin temperatures.

Large arrays extend the primary thermometry regime beyond the universal limit.

Charge offset effects are mitigated in larger arrays, improving low-temperature accuracy.

Abstract

The charge localization of single electrons on mesoscopic metallic islands leads to a suppression of the electrical current, known as the Coulomb blockade. When this correction is small, it enables primary electron thermometry, as it was first demonstrated by Pekola et al. (Phys. Rev. Letters, 73, 2903 [1994]). However, in the low temperature limit, random charge offsets influence the conductance and limit the universal behavior of a single metallic island. In this work, we numerically investigate the conductance of a junction array, and demonstrate the extension of the primary regime for large arrays, even when the variations in the device parameters are taken into account. We find that our simulations agree well with measured conductance traces in the submillikelvin electron temperature regime.