Coulomb Interaction Engineering at YBa$_{2}$Cu$_3$O$_{7-\delta }$-SrTiO$_{3}$ 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 $$T_c$$T c . To check this hypothesis, we investigated structural and transport properties of YBa $$_{2}$$2 Cu $$_{3}$$3 O $$_{7-\delta }$$7 - δ (YBCO) thin films sandwiched between SrTiO $$_{3}$$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 $$T_c$$T c up to $$\Delta$$Δ T $$\approx$$≈ 20 K was observed at these interfaces in case of underdoped YBCO films.