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Thursday, March 28

Theoretical Studies of Oxide Heterostructures

Zhicheng Zhong, Institute of Solid State Physics, Vienna University of Technology
Materials Science and Technology Division, Materials Theory Group, Seminar
11:00 AM — 12:00 PM, Chemical and Material Sciences Building (4100), Room J-302
Contact: Satoshi Okamoto (okapon@ornl.gov), 865.576.1317

Abstract

In 2004, Ohtomo and Hwang found a metallic interface with high carrier mobility between two insulating perovskite oxides, LaAlO3(LAO) and SrTiO3(STO). This interface continues to attract much attention with reports that it can be conducting, strong spin-orbit coupled, magnetic, or even superconducting. In contrast to the striking experimental observations, the physical origin of this metallic behavior is still the subject of intense debate. Two types of doping mechanisms are proposed to account for the conducting behavior: pure charge transfer or the creation of oxygen vacancies and other defects. There is experimental support for both mechanisms, but some critical evidence is also missing. In this talk I will present a single framework that can naturally reconcile these two doping mechanisms as well as the corresponding experimental evidence.

In addition, I will present our theory of spin-orbit coupling (SOC) at LAO interfaces and STO surfaces. We find that LAO/STO has peculiar SOC properties arising from the multi-orbitals character which are absent in the standard single-band description as for the nearly free two-dimensional electron gas in semiconductor heterostructures.