Nonlinear Meissner Interferometry

We propose a nonlinear Meissner interferometer in which a high-Q superconducting resonator is excited by the third harmonic generated by the nonlinear Meissner response in a superconducting film. This effect can be used to greatly increase the field amplitude of the nonlinear electromagnetic response and generate a giant third harmonic at GHz frequencies. We calculated the resonance line of the third harmonics B_3ω(T) and showed how the measurements of the temperature dependence of B_3ω(T) can reveal the fundamental mechanisms of the nonlinear Meissner effect and superconducting gap symmetry in conventional and unconventional superconductors.