The quantum behavior of superconducting nanowires may essentially depend on the employed experimental setup. Here we investigate a setup that enables passing equilibrium supercurrent across an arbitrary segment of the wire without restricting fluctuations of its superconducting phase. The low-temperature physics of the system is determined by a combined effect of collective soundlike plasma excitations and quantum phase slips. At $T=0$ the wire exhibits two quantum phase transitions, both being controlled by the dimensionless wire impedance $g$. While thicker wires with $g>16$ stay superconducting, in the thinnest wires with $g<2$ the supercurrent is totally destroyed by quantum fluctuations. The intermediate phase with $2<g<16$ is characterized by two different correlation lengths demonstrating superconductinglike behavior at shorter scales combined with vanishing superconducting response in the long scale limit.

• Received 22 May 2019
• Revised 15 July 2019

DOI:https://doi.org/10.1103/PhysRevB.100.014520