Enhancement of the critical current of intrinsic Josephson junctions by carrier injection

Abstract

We present a study of the doping effect by carrier injection of high-T c superconducting Bi-based whiskers. The current was injected in the c-axis direction, i.e., perpendicular to the superconducting planes. Superconducting properties were investigated systematically as a function of the doping level. The doping level of one and the same sample was changed by current injection in very small steps from an underdoped state up to a slightly overdoped state. We have observed that T c versus log (j c ) exhibits a dome-shaped characteristic, which can be fitted by a parabola. As T c versus carrier concentration has a parabolic form, too, it can be concluded that the critical current density j c increases exponentially with the doping level. The electron-trapping mechanism is interpreted in the framework of Phillips' microscopic theory. In addition, the Joule heating effect in the intrinsic Josephson junction (IJJ) was controlled by carrier injection, and the effect of the non-equilibrium quasiparticle on the I-V curves of the IJJs was also discussed.

Interlayer tunneling spectroscopy of mixed-phase BSCCO superconducting whiskers

“…It can be clearly seen that the carrier injection effect caused an increase of I c , while Δ s decreased with increased doping level. This increase of I c is in good agreement with our earlier study [30] and also with several studies in the literature indicating that the c-axis critical current density, J c , changes exponentially with the doping level or oxygen excess δ [31][32][33]. Moreover, we observe that the J c values that can be calculated from figure 8(b) lie in the range J c = (4.7-6.4) × 10 2 A cm −2 , which all fall into the underdoped regime [29].…”

“…Doping of the crystal stack by carrier injection led to an increase of ∼24% for the I c of the IJJs, but the doping inhomogeneity for the different junctions was preserved. The doping inhomogeneity among the junctions in the underdoped regime is a well-known scenario, and it gradually disappears as the doping rate approaches the overdoped regime [7,30]. Additionally, it can be seen that the voltage value, at which superconductivity disappeared, shifted to lower values.…”

Tuning THz emission properties of Bi2Sr2CaCu2O8+δintrinsic Josephson junction stacks by charge carrier injection

“…For small stacks, with lateral dimensions of a few μm consisting of some 10 IJJs, it was shown that the charge carrier concentration can be changed reversibly in situ by heavy current injection [62][63][64][65]. The effect is different from electromigration and oxygen diffusion and presumably related to the (un)filling of charge traps in the insulating layers [62,63].…”