The current-phase relation in Josephson junctions

TLDR

This review provides a theoretical basis for understanding the current‑phase relation (CΦR) of the dc Josephson effect in various superconducting junctions. The authors review recent theoretical developments on how deviations from the sinusoidal CΦR arise, and describe a method that measures electrical currents in junctions with coupling energies smaller than thermal energy. The review introduces a new experimental tool for measuring the CΦR and demonstrates its importance for fundamental physics and practical applications through several examples.

Abstract

This review provides a theoretical basis for understanding the current-phase relation (C\ensuremath{\Phi}R) for the stationary (dc) Josephson effect in various types of superconducting junctions. The authors summarize recent theoretical developments with an emphasis on the fundamental physical mechanisms of the deviations of the C\ensuremath{\Phi}R from the standard sinusoidal form. A new experimental tool for measuring the C\ensuremath{\Phi}R is described and its practical applications are discussed. The method allows one to measure the electrical currents in Josephson junctions with a small coupling energy as compared to the thermal energy. A number of examples illustrate the importance of the C\ensuremath{\Phi}R measurements for both fundamental physics and applications.