Title：‘Unconventional’ Superconductivity in Oxide Quantum Materials and Heterostructures

Speaker：Danfeng Li, Department of Applied Physics, Stanford University

Date：June 8, 9：30AM

Tencent meeting：Meeting ID: 217 338 908；Link：https://meeting.tencent.com/s/FOtsGNzUoH2Q

Abstract：Developing new techniques to design and discover novel quantum materials and architectures poses an exciting frontier in condensed-matter research. In particular, synthesis of additional superconductors, especially those with unusual symmetries of superconducting order parameters and/or exotic pairing mechanisms, opens new doors to future applications in quantum devices. In this seminar, I will present research efforts on atomic-scale growth and engineering of such unconventional superconductors in complex oxide heterostructures, built on two extraordinary examples: SrTiO₃and nickelates. In the first part, I will elucidate the “polar catastrophe” scenario as the origin of the two-dimensional electron system at the celebrated LaAlO₃/SrTiO₃interfaces and discuss low-dimensional superconductivity in the related heterostructures. I will also review the on-going investigations on the nature of SrTiO₃superconductivity and their implications. In the second part, I will present the recent observation of superconductivity in an infinite-layer nickelate compound [D. Li et al., Nature 572, 624 (2019)] and the study of its superconducting phase diagram. This system is of particular interest due to its potential relationship with the high-T_ccuprate superconductors, in that they share a similar crystal structure and starting electronic configuration. I will also highlight the key aspects of its electronic and magnetic structures, which are inherently distinct from cuprates. Finally, I will suggest how new applications of kinetic-based synthetic approaches in oxide heterostructures provide a broad opportunity to create novel quantum systems in previously inaccessible ways.