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We utilize the short pulse interlayer tunneling spectroscopy on a 60 ns time scale for the Bi2Sr2CaCu2O8+δ system. The results indicate that the influence of self-heating is negligible up to an injection current density of ∼60 kA/cm2 and an injection power areal density of ∼90 kW/cm2. By means of this technique, we are able to observe the superconducting gap, the pseudogap, and the dip-and-hump structure precisely with little influence from the self-heating.

Interlayer tunneling spectra, the Josephson critical current density J c , and the normal tunneling resistance have been measured simultaneously for intrinsic Josephson junctions in Bi 2 Sr 2 CaCu 2 O 8+δ over a wide range of doping using a small mesa structure and a short-pulse technique. It is found that J c decreases by nearly two orders of magnitude in the underdoped region. Experimental J c is found to show a significant deviation from the theoretical estimates. In order to interpret the result, we propose a model in which the superconducting order parameter is inhomogeneous in k space rather than in real space. Based on this model, quasiparticle current-voltage characteristics are calculated, giving a qualitative agreement with the experiment.

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