Science Diliman, Vol 11, No 2 (1999)

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Evidence of a Normal-State Pseudogap in Bulk Superconducting Tunneling Junctions of YBa2Cu3O7-δ

Leandro Guerra, Mildred Reyes, Ayn Manuel, Roland Sarmago, Arnel Salvador


Planar contact tunneling experiments have been performed on bulk superconducting tunneling junctions of YBa2Cu3O7-δ in the temperature range 77 -295K. A clear depression in the conductance curves measured, attributed to the pseudogap, has been observed in temperatures above Tc (approx. 90K determined from dc resistivity measurements) before disappearing at T*=275K. The width of the pseudogap has been quantitatively measured as Dps, ave = 25.6meV from the differential conductance plots. These results agree with the current understanding of the phenomenology and nature of this pseudogap, namely: (I) the pseudogap value is relatively temperature-independent; (2) the superconducting gap and the pseudogap have the same d-wave nature; and (3) the superconducting gap evolves from the pseudogap.

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