Session XC24 - Josephson Junction Theory.
ORAL session, Friday morning, March 26
Room 172W, GWCC
It has been shown by Aharonov and Bohm that the electromagnetic potentials cause observable interference effects in quantum mechanics. As a result of the gauge invariance, the magnetic flux is quantized in units of hc/|e|, while the potential difference is quantized in units \hbar/e. Meanwhile, the magnetic flux in the Josephson effect is quantized in units of hc/2|e| rather than hc/|e| and the frequency of the alternative current in the alternative Josephson effect is in units of \hbar/2e rather than \hbar/e. It is widely believed that those results are clear evidences of Cooper's pairing in superconductors, where electrons are bound in pairs and the pairs with the charge 2e are the charge carriers in the superconductors. It is shown here in terms of the geometric phase-Barry's phase that the factor of 2 in 2e in the stationary and alternative Josephson effects is an outcome of both the Londons equations and gauge invariance.