SURFER · Superconducting and ferroelectric two-dimensional electron gases (2DEGs) at oxide interfaces.

In the project “SURFER”, we will demonstrate the coexistence of antagonistic properties namely superconductivity (SC) and ferroelectricity (FE)” and the enhancement of superconducting transition temperature (TC) through coupling with FE in oxide two-dimensional electron gases (2DEGs). So far, this coupling has almost only been observed in bulk oxides and in thin films of doped SrTiO3 (STO) where no ferroelectric switching is possible due to the three-dimensional distribution of carriers. The origin of SC and enhanced TC due to coupling between FE and SC is still not clarified, which might be because only one material (STO) system has been studied. In SURFER, we aim to realize ferroelectric and superconducting oxide 2DEGs with enhanced superconducting properties that are also switchable with FE present in these systems. With this aim, we will explore three new oxide 2DEG systems that have not been studied so far which will be fabricated based on different ferroelectric materials (1. STO thin films. 2. BaTiO3, and 3. Niobium (Nb)-substituted KTaO3) by growing on top a thin metal or oxide overlayer. In addition to the experimental realization of oxide 2DEGs hosting such interesting properties, this project will also help us to gain a clear understanding about the origin of SC and enhanced TC, due to FE and SC coupling in oxides which is a longstanding question by investigating the properties of these material systems in detail.