Microwave emission due to anisotropic quasiparticle injection into an ErBa/sub 2/Cu/sub 3/O/sub y/ superconductor

We report the observation of microwave emission and the dc measurements on tunnel injection of quasiparticles into a ErBa/sub 2/Cu/sub 3/O/sub y/ (EBCO) thin film using the samples with antenna geometry which are nearly free from the parallel overlapping effect of the injector current and the thin film current. The injector consists of two EBCO/insulator/Au (S/I/N) gate junctions. The samples were fabricated by lift-off photolithography technique. The microwave emission intensity from the junction was measured under the condition of broadband non-resonant matching using a superheterodyne radiometric receiver at frequencies f/sub REC/=36 GHz and 47 GHz. The detected microwave emission power increased nearly linearly with the injection current. The emitted power was greater for the higher receiving frequency. The observed maximum emitted broad band spectrum power at frequency f/sub REC/=47 GHz was about 10 pW for an integrating time of 1 sec. The phenomenon is discussed in terms of the nonequilibrium dynamics together with the ionic nature of oxide superconductor.