Three terminal YBaCuO Josephson device with quasi-particle injection gate

Quasiparticle injection effects in YBa2Cu3Ox-based planar structures at high operating temperatures

“…In previous studies of the injection effect in controlled weak-link structures [2][3][4] narrowest part of the bridge was an order of magnitude larger than the length of the gate. In this case the generated "normal" overheated zone in the gatecontact area propagates along the bridge with thermal speed, yielding a voltage drop proportional to the length of the bridge.…”

“…A current gain of 95 was found in low-T¢ weak-link structures [2,3]. A first study of quasiparticle injection in HTS YBCO/A1 structures shows a current gain of 5-7 at 4.2 K [4].…”

Quasiparticle injection effect of aYBa2Cu3O7−

“…[2][3][4] Previous studies on the nonequilibrium state of high-T c superconductors by quasiparticle injection current, however, have so far not provided useful information, because of the imperfect geometries in these measurements. In previous reports, [5][6][7][8][9] most measurements were performed using samples with cross-line junction geometry. In this geometry, both the injection current and the transport current flow in a YBCO film in parallel, yielding a pairbreaking effect by the injection current itself as well as by the transport current, which made the observed characteristics quite asymmetric with respect to the direction of current flow.…”

“…The observed characteristics were nearly symmetric with respect to the relative direction of the injection current and the film critical current, in contrast to previous reports. [5][6][7][8][9] It is understood that, since J c (J inj ϭ0)ϵJ c0 ӷJ inj (J c ϭ0)ϵJ ic , the quasiparticle injection effect is significantly greater than the current pair-breaking effect for this sample, even if some current spread is taken into account. At 4.2 K the YBCO film critical current (I c ϭ62 mA) was suppressed to zero at critical injection current I inj ϭI ic ϭ30 mA, and the current gain as defined by I c /I ic was about 2.…”

“…5,16 For the injection power of R n I inj 2 , the effective recombination time eff is approximately given by 3.2N(0)⌬ 0 2 bw 1 w 2 d/FR n I inj 2 at low reduced temperatures, by assuming the normalized critical excess quasiparticle number density n c ϭ0.394, 15 where N(0) is the single-spin density of states at the Fermi level, ⌬ 0 is the gap parameter, d is the YBCO film thickness, F is the conversion factor, and b is the ratio of the measured film critical current density to the best one so far reported (Ͼ10 7 A/cm 2 ). The last factor was taken into account because the films did not correspond to the best quality, whose carrier density would be given by N(0)⌬ 0 .…”