The magnetic-field-tuned quantum superconductor-insulator transitions of disordered amorphous indium oxide films are a paradigm in the study of quantum phase transitions and exhibit power-law scaling behavior. For superconducting indium oxide films with low disorder, such as the ones reported on here, the high-field state appears to be a quantum-corrected metal. Resistance data across the superconductor-metal transition in these films are shown here to obey an activated scaling form appropriate to a quantum phase transition controlled by an infinite-randomness fixed point in the universality class of the random transverse-field Ising model. Collapse of the field-dependent resistance vs temperature data is obtained using an activated scaling form appropriate to this universality class, using values determined through a modified form of power-law scaling analysis. This exotic behavior of films exhibiting a superconductor-metal transition is caused by the dissipative dynamics of superconducting rare regions immersed in a metallic matrix, as predicted by a recent renormalization group theory. The smeared crossing points of isotherms observed are due to corrections to scaling which are expected near an infinite-randomness critical point, where the inverse disorder strength acts as an irrelevant scaling variable.
Bibliographical noteFunding Information:
The authors would like to thank R. Fernandes and S. Kivelson for helpful discussions. The work at Minnesota was 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 Award No. ECCS-1542202. T.V. acknowledges support by the National Science Foundation under Grants No. DMR-1506152, No. PHY-1125915, and No. PHY-1607611. 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.