All-YBa2Cu3O7 trilayer tunnel junctions with Sr2AlTaO6 barrier

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Abstract
A new barrier material, Sr2AlTaO6, was employed in fabricating all‐YBa2Cu3O7 trilayer tunnel junctions using in situ coevaporation and sputtering deposition. It was found that the superior material properties of Sr2AlTaO6 allow the use of a very thin barrier layer. A dramatic increase in the quasiparticle density of states at the YBa2Cu3O7 superconductive gap was observed for the first time from thin‐film all‐YBa2Cu3O7 devices. Well‐defined gap structures were observed at temperatures up to 47 K. The tunneling characteristics are consistent with the typical superconductor‐insulator‐superconductor behavior. The temperature dependence of the superconductive gap is compared with the BCS theory.