Vector Potential Coupling From Outside the Loop Through the Superconducting Shield

We tested whether the Maxwell-Lodge effect, a classical version of the Aharonov-Bohm effect, occurs even when electromagnetic shielding is provided by a superconducting tube. A long, thin superconducting solenoid coil was confined inside a lead tube so that there was no flux leakage from the coil ends. The double semi-circular vector potential coils ensure that 1) there is no local magnetic field at the location of the copper wire in the secondary coil and 2) there is no magnetic flux inside the loop of the secondary coil. Three different materials with different permeability were used for the core. A coaxial wire secondary coil shielded by a lead tube was placed orthogonally to the center of the semicircle of the primary coil. The voltage generated in the secondary coil at 4.2 K was only reduced to about 1/10 of 300 K. This coupling between the primary and secondary coils is due to the vector potential, since it cannot be completely shielded even with a superconducting shield.