INTRINSIC FLUCTUATIONS IN SUPERCONDUCTING RINGS CONTAINING ONE-DIMENSIONAL WEAK LINKS

The Langer-Ambegaokar statistical theory of dissipative fluctuations in narrow superconducting channels is extended to describe the quantum transitions of a closed superconducting ring containing a long one-dimensional weak-link section. The external magnetic flux e linking the loop is the independent thermo-dynamic variable. Based upon the Ginzburg-Landau free energy, the theory is expected to accurately describe single-quantum transitions for T near but slightly below Tc. Data reported by Lukens and Good-kind for thin-film Sn rings are reasonably consistent with the theory, but more definitive experimental tests are required. © 1969 The American Physical Society.