Conditions for observing Shapiro steps in a Bi2Sr2CaCu2O8+δ high-Tc superconductor intrinsic Josephson junction: Numerical calculations

Abstract

Conditions to observe Shapiro steps clearly and stably are studied for an intrinsic Josephson junction (IJJ) in Bi2Sr2CaCu2O8+δ high-Tc superconductors. The current equation normalized by the critical current Ic(T) is solved fully numerically. In the calculations, the quasiparticle tunneling current is evaluated by using the normalized I−V characteristics obtained within the d-wave symmetry superconducting gap, while the Cooper-pair (CP) one is calculated on the basis of the general way in which the coherent and incoherent CP tunneling currents can be correctly calculated within the d-wave treatment and the current due to thermal noises is also simulated by using normal random numbers. It is found that the product SRshunt of the junction cross section S and the shunt resistance Rshunt, and the critical current density Jc are important junction parameters, and moreover, that the current equation of the IJJ with no shunt resistance depends on only a universal curve μ(i0) as a function of the normalized external dc current i0. Furthermore, the effects of the noise, the normalized CP tunneling currents, the SRshunt product, the normalized amplitude ir of external ac modulation, and the Jc on observing the Shapiro steps are studied. When the IJJ is operated under the condition that the shunt resistance is added and the external ac modulation frequency fr is higher than the plasma frequency fp, it is found that (1) clear and stable Shapiro steps with good responses are obtained within the wide range of ir, (2) the response does not so largely depend on the value of SRshunt, and (3) the response for the high Jc junction is much better than that for the low one.

Source-reported materials — not catalogue approval

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