System for fast time-resolved measurements of c-axis quasiparticle conductivity in intrinsic Josephson junctions of Bi2Sr2CaCu2O8+δ

A wide-band cryogenic amplifier measurement system for time-resolved four-point current-voltage (I-V)-characteristic measurements on Bi2Sr2CaCu2O8+δ mesa structures is described. We present measurements which demonstrate the importance of self-heating on ∼50 ns time scales. Such heating is likely to have been very significant in many previously published measurements, where the reported nonlinear I-V characteristics have been used to derive superconducting energy gaps.