InOx films that are less disordered than those exhibiting direct quantum superconductor-insulator transitions feature quantum superconductor-metal transitions tuned by magnetic field. Resistance data across this superconductor-metal transition obey activated scaling, with critical exponents suggesting that the transition is governed by an infinite-randomness critical point in the universality class of the random transverse-field Ising model in two dimensions. The transition is accompanied by quantum Griffiths effects. This unusual behavior is expected for systems with quenched disorder in the presence of ohmic dissipation. Disorder leads to the formation of large rare regions which are locally ordered superconducting puddles dispersed in a metallic matrix. Their dissipative dynamics causes the activated scaling, as predicted by a renormalization group theory.
Bibliographical noteFunding Information:
The work at Minnesota was financially supported by the National Science Foundation under grants no. DMR-1209578 and no. DMR-1704456. Portions of this work were conducted in the Minnesota Nano Center, which is supported by the National Science Foundation through the National Nano Coordinated Infrastructure Network (NNCI) under grant no. ECCS-1542202. T.V. acknowledges support by the National Science Foundation under grants no. DMR-1506152, no. DMR-1828489, no. PHY-1125915, and no. PHY-1607611.
The authors would like to thank R. Fernandes, B. Spivak, and S. Kivelson for helpful discussions. He also acknowledges hospitality of the Kavli Institute for Theoretical Physics, Santa Barbara, and the Aspen Center for Physics, where parts of the work were performed.
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- Quantum Griffiths effects
- Quenched disorder
- Superconductor-metal transitions