Controllable Complex Oxide Hetero-interfaces
1材料科學工程系, 交通大學, 新竹, Taiwan
2物理所, 中央研究院, 台北, Taiwan
3電子物理系, 交通大學, 新竹, Taiwan
* presenting author:朱英豪,
Interfaces have emerged as key focal points of current condensed matter science. In complex correlated oxides, heterointerfaces provide a powerful route to create and manipulate the charge, spin, orbital, and lattice degrees of freedom. The most common interfaces that have been explored are artificially constructed heterointerfaces. The interaction of these degrees of freedom at the heterointerface has resulted in a number of exciting discoveries including the observation of a 2-D electron gas-like behavior at LaAlO3-SrTiO3 interfaces, the emergence of the ferromagnetism in a superconducting material at YBa2Cu3O7-x-La0.7Ca0.3MnO3 interfaces and induced ferromagnetism at BiFeO3- La0.7Sr0.3MnO3 interfaces. Among them, the interface of YBa2Cu3O7-x-La0.7Ca0.3MnO3 heterostructures has been intensively studied to understand the proximity effect between ferromagnets and superconductors. One key question has yet to be addressed in this prominent YBa2Cu3O7-x-La0.7Ca0.3MnO3 system: does termination type play an important role in determining the superconducting and magnetic properties? In this talk, we present our studies of YBa2Cu3O7-x-La0.7Ca0.3MnO3 heterostructures with two distinct types of interfacial termination, thus suggesting control of thin film growth at the nanocale. The superconducting and magnetic properties exhibit different responses depending on the type of termination. Based on X-ray scattering, we have found that the magnetic interaction only happens at a particular termination. Cross-sectional scanning tunneling microscopy has been used to study the proximity effect. We found that the competition of superconductor and ferromagnet is different at the two distinct interfaces. Moreover, in the push for practical applications, it is desirable to have the ability to control the interface functionalities by an external stimulus. Therefore we also present our studies of LaAlO3-SrTiO3 interfaces as a model system for controlling functionalities by an external stimulus. Two pathways including non-volatile ferroelectric control and visible-light control of the metal-insulator transition will be demonstrated. These studies open a new avenue to design and engineer new functional oxide interfaces.

Keywords: heterointerface, complex oxides, epitaxial