The I C R N Value in Intrinsic Josephson Tunnel Junctions in Bi2Sr2CaCu2O8+δ (Bi2212) Mesas

Abstract

The c-axis current-voltage I (V ) characteristics have been obtained on a set of mesas of varying height sculpted on Bi 2 Sr 2 CaCu 2 O 8 + δ (Bi2212) crystals intercalated with HgB 2 . The intercalation, along with the small number of junctions in the mesa, N = 6-30, minimizes the degree of self-heating, leading to a consistent Josephson critical current, I C , among junctions in the mesa. The Bi2212 crystals with a bulk T C = 74 K are overdoped and display negligible pseudogap effects allowing an accurate measure of the normal state resistance, R N . These properties make the mesas nearly ideal for the determination of the Josephson I C R N product. We find I C R N values consistently ∼30% of the quasiparticle gap parameter, /e, which was measured independently using a mechanical contact, break junction technique. The latter was necessitated by higher bias heating effects in the mesas which prevented direct measurements of the superconducting gap. These values are among the highest reported and may represent the maximum intrinsic value for I C R N . The results indicate that the c-axis transport is a mixture of coherent and incoherent tunneling.

Terahertz wave emission from intrinsic Josephson junctions in high-Tcsuperconductors

“…In figure 5, the contact resistance can be seen in our data below T c due to our three-point measurements: it is usually < 5 except for one sample (w = 40 μm). A recent study on 10×10 μm 2 mesas show the contact resistance to be a superconductor-insulator-normal-metal junction that can be expected to be weakly temperature-dependent above T c and diverge at low temperatures [29]. Values range from 0.00015 to 0.0005 cm 2 .…”

Intrinsic tunneling study of underdoped Bi 2 Sr 2− x La x CuO 6+δ superconductors

“…However, intrinsic tunneling studies using IJJs have been severely hampered by the selfheating effect due to the materials' poor thermal conductivity and relatively large current density needed to reach the gap voltage, which is evidenced in both Bi2212 [12−19] and Bi2201 [20−22] IJJs experiments. To solve the problem, many efforts including using intercalated crystals, [12,19] short-pulse measurements, [13,14] and reducing the IJJs sizes [15,17,18] have been made.…”