Coulomb Interaction Engineering at YBa2Cu3O7-δ-SrTiO3 Interface.

It has been proposed by Müller and Shengelaya that underdoped ultrathin layers of copper-oxide high-temperature superconductors (HTSs) sandwiched between high-dielectric-constant insulator layers could manifest increased superconducting critical temperature T c . To check this hypothesis, we investigated structural and transport properties of YBa 2 Cu 3 O 7 - δ (YBCO) thin films sandwiched between SrTiO 3 (STO) layers. Scanning transmission electron microscopy (STEM) showed that a high-quality interface is formed between YBCO and the top STO layers. An increase of T c up to Δ T ≈ 20 K was observed at these interfaces in case of underdoped YBCO films. [ABSTRACT FROM AUTHOR]