High transition temperature superconducting surface acoustic wave devices

Thin films of high transition temperature superconducting YBa2Cu3O7−δ (YBCO) have been deposited onto YZ-cut LiNbO3 and photolithographically patterned into surface acoustic wave (SAW) devices operating at 50 and 100 MHz center frequencies. Both devices show sharp improvement in SAW transduction efficiency as temperatures are lowered to the superconducting transition temperature of the YBCO electrodes. The magnitude of the improvement is directly dependent on the normal state resistance of the YBCO, and in one case was as high as 12 dB. In both cases, the amplitude change over the entire temperature range is matched nearly exactly by the derived ideal electrode behavior predicted from the aperture width, substrate radiation resistance, and YBCO electrode sheet resistance.