Quantum fluctuations in thin superconducting wires of finite length

In one dimensional wires, fluctuations destroy superconducting long-range order and stiffness at finite temperatures; in an infinite wire, quasi-long range order and stiffness survive at zero temperature if the wire's dimensionless admittance $\mu$ is large, $\mu > 2$. We analyze the disappearance of this superconductor-insulator quantum phase transition in a finite wire and its resurrection due to the wire's coupling to its environment characterized through the dimensionless conductance $K$. Integrating over phase slips, we determine the flow of couplings and establish the $\mu$--$K$ phase diagram.Comment: 4 pages, 2 figure

Reply to the Comment on 'Quantum Phase Slips and Transport in Ultra-Thin Superconducting Wires'

We reply to the recent Comment [cond-mat/9702231] by J.-M. Duan. Our point of view is markedly different on every issue raised. Much of the disagreement can be traced to a different preception of experimentally relevant length scales. i) We explain the difference between our formulation, which rests on a microscopic basis, and the phenomenological one of the author. ii) Our renormalization scheme is fundamentally right, as the "log(log)" interaction appears only in wires of astronomical lengths. iii) The tunneling barrier is profoundly reduced by the kinetic inductance. iv) We do make an appropriate comparison to the data on the thinnest available wires.Comment: 1 page Revte

Quantum Phase Slips in Superconducting Nanowires

We have measured the resistance vs. temperature of more than 20 superconducting nanowires with nominal widths ranging from 10 to 22 nm and lengths from 100 nm to 1050 nm. With decreasing cross-sectional areas, the wires display increasingly broad resistive transitions. The data are in very good agreement with a model that includes both thermally activated phase slips close to Tc and quantum phase slips (QPS) at low temperatures, but disagree with an earlier model based on a critical value of R_n/Rq. Our measurements provide strong evidence for QPS in thin superconducting wires.Comment: 9 pages, 3 figure