The knowledge of the surface resistance R s of superconducting thin film at microwave and terahertz (THz) regions is significant to design, make and assess superconducting microwave and THz electronic devices. In this paper we reported the R s of MgB 2 films at microwave and THz measured with sapphire resonator technique and the time-domain THz spectroscopy, respectively. Some interesting results are revealed in the following: (1) A clear correlation is found between R s and normal-state resistivity right above T c, ρ 0, i.e., R s decreases almost linearly with the decrease of ρ 0. (2) A low residual R s, less than 50 μΩ at 18 GHz is achieved by different deposition techniques. In addition, between 10 and 14 K, MgB 2 has the lowest R s compared with two other superconductors Nb 3Sn and the high-temperature superconductor YBa 2Cu 3O 7-δ(YBCO). (3) From THz measurement it is found that the R s of MgB 2 up to around 1 THz is lower than that of copper and YBCO at the temperature below 25 K. (4) The frequency dependence of R s follows ω n , where ω is angular frequency, and n is power index. However, n changes from 1.9 at microwave to 1.5 at THz. The above results clearly give the evidences that MgB 2 thin film, compared with other superconductors, is of advantage to make superconducting circuits working in the microwave and THz regions.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics