Direct Observation of Phase Oscillation Modes in Josephson-coupled   Layered Superconductors
  We have proposed to employ the microwave S parameters method to measure phase oscillation modes (POMs) in Josephson coupled-layered superconductors. For the first time, in SmBa2Cu3O7 (SmBCO) and YBa2Cu3O7-b (YBCO) at 77 K we have directly observed some POMs far below the Josephson plasma frequency. A series of discrete modes have been observed and discussed qualitatively in the POMs. The method may be a powerful and flexible tool in this field. 
Z. Y. Lai, X. Yao, X. H. Zeng, H. Zheng, W. Z. Shen, X. Y. Chen, and   H. G. Shen