What do the phase-sensitive experiments tell us?

TL;DR

This paper clarifies the limitations of phase-sensitive experiments in determining the pairing symmetry of Cooper pairs in cuprate superconductors and proposes a new explanation for observed phenomena.

Contribution

It introduces a novel interpretation of phase-sensitive experiments, emphasizing the distinction between condensate and pairing wavefunctions, and predicts new observable effects.

Findings

Phase-sensitive experiments do not conclusively prove d-wave pairing.

A new theoretical explanation for phase shifts is proposed.

Predictions of observable phenomena based on the new model.

Abstract

The phase-sensitive experiments on cuprate superconductors have told us about the symmetry of the condensate wavefunction. However, they can not determine the pairing symmetry of Cooper pairs. To describe a superconducting state, two wavefunctions are needed, condensate wavefunction and pairing wavefunction. The former describes the entirety movement of the pairs and the latter describes the relative movement of the two electrons within a pair. The $\pi$-phase shift observed in the phase sensitive Josephson measurements can not prove that the pairing state is d-wave. We present here a new explanation and predict some new observable phenomena.