Title: A few recent progresses in understanding the origin of electron gas at SrTiO₃-based heterointerfaces and the discovery of a new type of heterointerface

Speaker: Dr. Yanwu Xie

Time: Thursday, Oct. 17, 10:30 am

Venue: Room 242, East Lecture Building 4-242, Zijingang Campus

Abstract: The electron gas at the heterointerface of LaAlO₃/SrTiO₃ has attracted intense research interests in the past 15 years. However, its origin is still under hot debate. A compromise explanation is to combine an intrinsic scenario of polar-discontinuity-induced electronic reconstruction and an extrinsic scenario of oxygen vacancies in SrTiO₃. Unfortunately, this explanation is still inconsistent with quite a few nontrivial experimental observations, particularly in explaining the electron gases at heterointerfaces other than LaAlO₃/SrTiO₃. In this talk, I will present our recent progresses in understanding the origin of these electron gases. The key point is to take into account the oxygen vacancies in the films grown on SrTiO₃. With this idea, almost all the puzzles observed in previous studies can be well explained. Finally, I will give a short introduction about our newly discovered electron gas at the CaHfO₃/SrTiO₃ heterointerface. This electron gas is different from all the previous ones in that it is insensitive to the termination of SrTiO₃, and extremely robust against polar adsorbates and annealing in oxygen. A preliminary explanation of its origin will be discussed.