The anomalous Darwin term, one of the recently derived relativistic corrections to the conventional theory of superconductivity, is analyzed in detail. This analysis leads to the prediction of unusual types of fluctuations, of relativistic origin, in superconductors. An alternative derivation of the anomalous Darwin term, much simpler than that given originally, is presented and used to clarify some puzzling features of the original derivation. The question of observability of the anomalous Darwin term and the relativistic fluctuations is discussed and the relation to the conventional Darwin term and to earlier proposed superconducting Darwin terms is clarified.

• Received 27 July 2000

DOI:https://doi.org/10.1103/PhysRevB.63.052503