Emission of the THz waves from large area mesas of superconducting Bi2Sr2CaCu2O8+δ by the injection of spin polarized current

Rectangular Au/Co/Au/Bi2Sr2CaCu2O8+δ (Bi2212) mesa structures with large areas and high thicknesses were fabricated on as-grown Bi2212 single crystals in order to obtain small critical current from as-grown mesas by the injection of spin polarized current and so eliminate the adjustment of doping level for successful THz emission. We have performed c-axis resistance versus temperature (R–T), current–voltage (I–V) characteristics and bolometer measurements. It is the first time that THz emission has been observed from as-grown mesas due to injection of spin polarized current.

► THz emission was achieved from as-grown mesas due to injection of spin polarized current.
► Bump in return branch of I–V curve was observed due to radiation.
► The necessity of adjustment of doping level for THz emission was eliminated.