Tunneling spectra of underdoped Bi 2 Sr 2 Ca 1− x Y x Cu 2 O 8+δ intrinsic Josephson junctions

Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi2Sr2Ca1 xYxCu2O8+ single crystals with a Tc of 80 K. Tunneling spectra at the temperatures ranging from 4.2 K to 295 K are measured. A pulse technique is used to reduce sample heating for the measurement near pseudogap opening temperature T 280 K. Our experimental results show that the superconducting gap, the peakdip separation, and the pseudogap opening temperature are all increased as compared with those from near optimally doped samples, which requires further theoretical analysis in the future.