Terahertz surface impedance of thin YBa2Cu3O7 superconducting films

Using coherent terahertz time‐domain spectroscopy, we measure the surface impedance of 500‐A‐thick unpatterned superconducting YBa2Cu3O7 films in the normal and the superconducting state. Both real and imaginary parts of the surface impedance are measured simultaneously from the amplitude and phase changes of the terahertz bandwidth pulses transmitted through the superconducting films.