Short-Pulse Intrinsic Tunneling Spectroscopy in Bi₂Sr₂CaCu₂O_8+δunder Suppressed Self Heating

Abstract

Short-pulse tunneling spectroscopy on a time scale of 300 ns has been conducted using intrinsic Josephson junctions naturally built in the crystal structure of a slightly underdoped Bi2Sr2CaCu2O8+δ (Bi2212) by fabricating a very small and thin mesa of 6 nm in thickness and less than 5 µm in square width. The results are characterized by a pronounced superconducting peak at 79 meV accompanied by a broad pseudgap at a much higher energy of 125 meV, indicating discrete nature of both energy structures. The temperature rise due to self-heating in a small mesa is numerically calculated based on temperature-dependent thermal conductivity and specific heat for each constituent material. It is found that the temperature rise is less than 2 K for the present experiment, which reinforces that the tunneling spectra obtained represent the genuine superconducting properties of Bi2212.

Method for Measuring Anisotropic Electrical Resistivity

“…It has been known that values for c measured for small and thin mesa structures tend to have a larger value than those obtained for bulk crystals. 6,7) It is stressed here that the present method can probe into a very small portion of a crystal that is more homogeneous and contains less imperfections than bulk crystals. In this sense, the present method can provide a different values for anisotropic resistivity.…”

“…A similar fabrication technique is found in the preparation of a mesa structure of intrinsic Josephson junction stacks for tunneling spectroscopy. 6,7) This method provides an effective means to measure the anisotropic resistivity for a highly anisotropic material of laminar shape or thin film. We have confirmed that this method is sufficiently practical by measuring the in-plane and out-of-plane resistivities of the high-T c superconductor Bi 2 Sr 2 CaCu 2 O 8þ , which we describe as an example at the end of this paper.…”

Terahertz Radiations and Switching Phenomena of Intrinsic Josephson Junctions in High-Temperature Superconductors: Josephson Phase Dynamics in Long- and Short-Ranged Interactions

“…We measured 𝐽 𝑐 and ITS in mesa-structured Bi 1.8 Pb 0.2 Sr 2 CaCu 2 O 8+ 𝛿 (BiPb2212) single crystals and compared the results with those previously obtained in pristine Bi2212 crystals. Figure 3 shows critical current densities in BiPb2212 and Bi2212 and the ratio 𝐽 𝑐 /𝐽 𝐴𝐵 𝑐 in the same carrier doping range [41]. The carrier doping 𝑝 was estimated from precise Hall-effect measurements in thin crystals with the identical nominal composition as the ITS measurements.…”