Current controlled high Tc superconducting switch

When a current is applied above the critical current lc of a superconductor, the material is in its normal state and has a finite resistance. Below lc the material becomes a superconductor with zero resistance. Switching between these two states can be achieved by modulating a current through the sample. Various high Tc superconducting (HTS) line structures have been made. In the normal state these structures are ordinary resistors with resistances ranging from 10 μ to 100 kμ. The critical currents are in the range 10 μA–100 mA. Switching behaviour has been observed in a simple divider circuit using the HTS lines at 77 K. Applications of the current controlled HTS switch to digital and logic circuits are discussed.