Microwave radiometry of a quantum-critical, hybrid Josephson array
Abstract
Arrays of Josephson junctions can be tuned through anomalous metallic, quantum-critical, and insulating regimes. We introduce a new experimental probe, capturing microwave radiation across all three regimes, using a two-dimensional array of superconductor-semiconductor hybrid Josephson junctions as a model system. Our approach allows in-situ calibration of the sample's circuit parameters and provides isolation from measurement back-action effects. We measure the radiation temperature of the anomalous metal, and find that it is hotter than both the quantum-critical and insulating regimes. We further show that the anomalous-metallic regime is more susceptible to additional heating than other regimes, explaining its emergence in otherwise thermalized systems. Turning to the quantum-critical regime, we discover nonlinear scaling of radiative noise with applied bias, consistent with theoretical predictions of universal non-equilibrium behavior at quantum critical points.
Cite
@article{arxiv.2409.09835,
title = {Microwave radiometry of a quantum-critical, hybrid Josephson array},
author = {Kristen W. Léonard and Anton V. Bubis and Melissa Mikalsen and William F. Schiela and Bassel H. Elfeky and William M. Strickland and Duc Phan and Javad Shabani and Andrew P. Higginbotham},
journal= {arXiv preprint arXiv:2409.09835},
year = {2026}
}
Comments
10+11 pages, 6+13 figures