Insights on dilute superconductivity in SrTiO₃ from electron tunneling spectroscopy

The origin of superconductivity in the oxide semiconductor SrTiO₃ has remained an open question for more than 50 years. Tunneling spectroscopy, which directly probes the electronic structure of the material, is a powerful technique to study superconductivity and pairing interactions. We have developed an approach using atomically designed interfaces to realize high-quality tunneling junctions, enabling the first high-resolution examination of the systematic carrier density evolution of the intrinsic electronic structure in SrTiO₃. I will discuss our experimental results examining the strength of the electron-phonon coupling, the structure of the superconducting gap, and the role of intrinsic spin-orbit coupling. These results provide insight on the nature of the highly mobile polaronic carriers and the superconducting condensate which they form.