Significantly enhanced superconductivity in monolayer FeSe films on SrTiO3(001) via metallic δ-doping

Abstract Superconductivity transition temperature (Tc) marks the inception of a macroscopic quantum phase-coherent paired state in fermionic systems. For two-dimension superconductivity, electrons condense into coherent superfluid at Tc, which is usually lower than pairing temperature, between intrinsic physics including Berezinskii-Kosterlitz-Thouless and pseudogap are hotly debated. In case monolayer FeSe superconducting films on SrTiO3(001), although (Tp) revealed to be 65–83 K by spectroscopy characterization, measured zero-resistance (${T}_{c}^0$) limited 20 K. Here, we report significantly enhanced superconductivity δ-doping Eu or Al SrTiO3(001) surface, ${T}_{c}^0$ 12 with narrowed width ΔTc ∼ 8 K, compared non-doped samples. Using scanning tunneling microscopy/spectroscopy measurements, demonstrate lowered work function δ-doped-SrTiO3(001) surface enlarged gaps improved morphology/electronic homogeneity. Our provides practical route enhance 2D interface engineering.