OBSERVATION OF PSEUDOGAP IN BI2SR2CACU2O8-CRYSTALS WITH ELECTRON-TUNNELING SPECTROSCOPY(DELTA SINGLE)

We report electron tunneling evidence for a pseudogap in the normal st ate excitation spectrum of as-grown Bi2Sr2CaCu2O8+delta (Bi2212) singl e crystals. The normalized conductance curves show that the gap struct ure does not disappear at T-c but at much higher temperature T; the l ower bound of T is within 110 K to 150 K for the investigated three j unctions. The result gives a support for the existence of paired carri ers in the normal state of cuprate superconductor Bi2212.