Tunneling spectra of underdoped Bi₂Sr₂Ca_1-xY_xCu₂O_8+\delta intrinsic Josephson junctions

Mesa-structured submicron intrinsic Josephson junctions are successfully fabricated and well characterized on underdoped Bi₂Sr₂Ca_1-xY_xCu₂O_8+\deltasingle crystals with a T_c 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.