Large-scale modulation in the superconducting properties of thin films due to domains in the SrTiO3 substrate

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Scanning superconducting quantum interference device measurements reveal large-scale modulations of the superfluid density and the critical temperature in superconducting Nb, NbN, and underdoped YBa2Cu3O7-delta films deposited on SrTiO3 (STO). We show that these modulations are a result of the STO domains and domain walls, forming below the 105 K structural phase transition of STO. We found that the flow of normal current, measured above the superconducting transition, is also modulated over the same domain structure, suggesting a modified carrier density. In clean STO, domain walls remain mobile down to low temperatures. Modulated superconductivity over mobile channels offers the opportunity to locally control superconducting properties and better understand the relations between superconductivity and the local structure.
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