Ramp-Edge Josephson Junctions Using Barriers of Various Resistivities(Special Issue on Superconductive Electron Devices and Their Applications)

概要

論文の詳細を見る
We have studied the effect of Ga and Ca substitution in the PrBa_2Cu_3O_δ(PBCO)barrier on the parameters of high-temperature-superconductor ramp-edge Josephson junctions. Pr_<1-x>Ca_xBa_2Cu_3O_δ(X=0.15, 0.3) had reduced bulk barrier resistivity as small as 10mΩcm which was close to the metal-insulator transition. Also, PrBa_2Cu<3-z>Ga_zO_δ, written as GaZ-doped PBCO(Z=0.15, 0.3, 0.6), had enhanced resistivity neater than 1kΩcm at 4.2K. The transport mechanisms in these bulk barriers fitted well with the Mott variable hopping model. The critical current density J_c and normalized junction conductance(R_nA)^<-1> decayed exponentially with almost the same decay length, as the barrier thickness incrased. The decay length depended on the barrier material, and ranged from 1.7nm to 6.5nm for J_c, from 1.9nm to 7.2nm for (R_nA)^<-1>. Because on these experimental results, we conclud that direct tunneling is the dominant transport mechanism for both quasi particles and paired particles in our junctions, while resonant tunneling should be considered as an additional transport mechanism of these two kinds of particles in the junctions with the PBCO-based barriers reported so far. It was also found that Ga doping raised the characteristic voltage V_c while Ca doping reduced it, though the V_c values obtained here were still small compared to the theoretically predicted values. The spacewise metal insulator transition at the interfaces caused by a high density of localized states in the barriers seemed to be responsible for the reduction in V_c. The best V_c value was 0.32mV at 77K and 5, 2mV at 4.2K using a Ga0.6-PBCO barrier. These V_c values are suitable for electronics applications. Furthermore, superconducting-gap-like structures were observed in the junctions with highly resistive Ga-doped PBCO barriers.
社団法人電子情報通信学会の論文
1998-10-25

Ramp-Edge Josephson Junctions Using Barriers of Various Resistivities(Special Issue on Superconductive Electron Devices and Their Applications)

スポンサーリンク

概要

著者

関連論文

スポンサーリンク