Spin-polarized quasiparticle injection into YBCO

FET-type devices have been fabricated by using trilayers of Nd0.7Sr0.3MnO3 (NSMO) or LaNiO, (LNO) (gate)/ LaAlO3 (LAO) (barrier) / Yba2Cu3O7 (YBCO) (channel) in order to investigate effect of quasiparticle injection into YBCO. Here, NSMO and LNO were used as gate electrodes for injection of spin-polarized and spin-unpolarized quasiparticles into the superconducting channel, respectively. When injecting along the c-axis of YBCO, the critical current was suppressed with spin-polarized qiiasiparticles 30 times more efficiently than with spin-unpolarized quasiparticles. Differential current gain, defîned as a differential change of the critical current to injection current change, has been achieved up to ∼ 16 for c-axis YBCO. If the response time is limited by quasiparticle relaxation time of ∼ 10 ps, the device may be useful for fast electronics. Preliminary high-speed measurements indicate that part of the critical current suppression may be caused by quasiparticle injection, not all by heating. When injecting along a-axis, no significant dependence on quasiparticle polarization was observed. Other superconductors such as Pr1.85Ce0.15CuO4 (PCCO) and Pbln have been tested in similar devices for comparison. © 1999 IEEE.