Imaging how fluctuations destroy superconductivity in two dimensions
Abstract
Two-dimensional superconductors test our understanding of quantum phases. Low-temperature "anomalous metal" states are widely observed where conventional theories predict only superconducting or insulating ground states. In model systems based on proximity-coupled Josephson junction arrays, the critical temperature falls far faster with decreasing normal-state conductance than predicted by existing models. Whether these observations indicate a new quantum phase, a need to refine models of disorder and fluctuations, or both remains unresolved. Using scanning magnetic susceptometry, we image the local superfluid phase stiffness ρs in gate-tunable Josephson junction arrays consisting of epitaxial Al islands on an InAs quantum well. Across six arrays and more than two orders of magnitude in the zero-temperature phase stiffness ρs0, the diamagnetic critical temperature Tc,φ is suppressed more strongly than can be explained solely by thermal phase fluctuations, scaling approximately as Tc,φ∝ρs00.3. While ρs is remarkably uniform at high carrier densities, at low carrier densities we find that anomalous metal transport emerges together with large-scale inhomogeneity that transport alone cannot directly detect. These results are inconsistent with a classical XY description within standard junction models, instead pointing to quantum fluctuations that suppress superconductivity throughout the superconducting phase and amplify inhomogeneity near the superconductor-insulator transition, producing anomalous metal behavior.
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BibTeX
@misc{horn2026imaging,
title = {{Imaging how fluctuations destroy superconductivity in two dimensions}},
author = {Logan Bishop-Van Horn and Teng Zhang and Sara Metti and Tyler Lindemann and Michael J. Manfra and Kathryn A. Moler},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2609.28837},
eprint = {2609.28837},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.28837},
}
RIS
TY - UNPB
TI - Imaging how fluctuations destroy superconductivity in two dimensions
AU - Logan Bishop-Van Horn
AU - Teng Zhang
AU - Sara Metti
AU - Tyler Lindemann
AU - Michael J. Manfra
AU - Kathryn A. Moler
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2609.28837
UR - https://arxiv.org/abs/2609.28837
AB - Two-dimensional superconductors test our understanding of quantum phases. Low-temperature "anomalous metal" states are widely observed where conventional theories predict only superconducting or insulating ground states. In model systems based on proximity-coupled Josephson junction arrays, the critical temperature falls far faster with decreasing normal-state conductance than predicted by existing models. Whether these observations indicate a new quantum phase, a need to refine models of disorder and fluctuations, or both remains unresolved. Using scanning magnetic susceptometry, we image the local superfluid phase stiffness ρ_s in gate-tunable Josephson junction arrays consisting of epitaxial Al islands on an InAs quantum well. Across six arrays and more than two orders of magnitude in the zero-temperature phase stiffness ρ_s0, the diamagnetic critical temperature T_c,φ is suppressed more strongly than can be explained solely by thermal phase fluctuations, scaling approximately as T_c,φ∝ρ_s0^0.3. While ρ_s is remarkably uniform at high carrier densities, at low carrier densities we find that anomalous metal transport emerges together with large-scale inhomogeneity that transport alone cannot directly detect. These results are inconsistent with a classical XY description within standard junction models, instead pointing to quantum fluctuations that suppress superconductivity throughout the superconducting phase and amplify inhomogeneity near the superconductor-insulator transition, producing anomalous metal behavior.
ER -