Publication Type:Journal Article
Source:IEEE Transactions on Applied Superconductivity, Volume 9, Number 2 PART 3, p.3640-3643 (1999)
Keywords:Critical current density (superconductivity), Critical current suppression, Differential current gain, Electric current measurement, Electromagnetic wave polarization, Electron transport properties, Electron tunneling, Gate electrodes, High temperature superconductors, Lanthanum aluminate, lanthanum compounds, Lanthanum niobate, multilayers, Neodymium compounds, Neodymium strontium manganate, Relaxation processes, Spin polarized quasiparticle injection, Superconducting channel, Superconducting devices, Yttrium barium copper oxides, Yttrium barium cuprates
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.
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