Nodal phase correlation and macroscopic quantum effects in superconducting rings

Abstract

We introduce the new concept of "nodal phase correlation" (NPC) into many-particle quantum mechanics. NPC is a particular quantum correlation among particles, which is important for current-carrying states of isolated systems. Mathematically it is characterized by a definite relation in configuration space between the phase and the modulus of the many-particle wave function. We illustrate the significance of NPC by showing the crucial role it plays in magnetic flux quantization and in certain macroscopic interference effects in superconducting rings. To this end we partly rederive the theory of these phenomena. Our method is based on the BCS theory. We critically examine previous work, in particular the single-particle pairing theory, which is considered to be a standard approach to magnetic flux quantization. This theory does not give rise to NPC. We are able to show that the corresponding many-particle wave function is in fact unrealistic and not consistent with the BCS theory of superconductivity.