Phase Diagrams of Superconducting Complex Oxides Studied via Electrostatic Tuning

Prof. Carlos A. R. Sa de Melo

School of Physics,
Georgia Institute of Technology

I discuss possible temperature versus filling factor phase diagrams of ultra-thin films or surfaces of bulk complex oxide superconductors, which are modeled via an extended attractive Hubbard model that allows pairing in three singlet channels: local s-wave, extended s-wave and d-wave. I will describe the accessible phases in the temperature versus filling factor phase diagram, which can change substantially depending on the ratio between local and near-neighbor attractions, producing regions with pure s-wave and d-wave symmetries, as well as regions with mixed s-wave and d-wave symmetries.  Some of the possible superconducting phases spontaneously break time reversal symmetry, and could be visited by changing temperature and/or filling factor. Lastly, I characterize some of the accessible phases via their superfluid density tensor and penetration depth, which might be measurable in the ultra-thin film or surface configuration.