Abstract
We explore the manifestation of quantum fluctuations across the superconductor-insulator transition (SIT) in three different local measurements: the two-particle density of states , compressibility , and diamagnetic susceptibility revealed through their local maps. The map of displays growing fluctuations upon increasing temperature as well as upon tuning the quantum tuning parameter , as expected, but remarkably, these fluctuations persist well below as the SIT is approached, indicating the quantum nature of these fluctuations. The map of paints a similar picture when tuned via , but in contrast to , we find a fundamental difference in its evolution with temperature, providing a complementary local probe to . , obtained using maximum entropy analytic continuation of Monte Carlo simulations on 2D quantum Josephson junction arrays, shows strongly diminished zero-energy spectral weight in nearly-insulating islands, correlating with regions of suppressed . We discuss the experimental implications of our results for scanning Josephson spectroscopy, compressibility, and scanning SQUID measurements in the context of quantum fluctuations.
- Received 28 February 2019
- Revised 31 March 2019
DOI:https://doi.org/10.1103/PhysRevB.99.144516
©2019 American Physical Society