钙钛矿氧化物异质界面制备及其超导电性调控研究

Heterointerfaces between perovskite oxides are emerging as one of the most interesting system in condensed-matter physics due to their intriguing physical properties, such as two dimensional electron gas, superconductivity and magnetism. The control of interfacial superconductivity would help to deepen the understanding of unconventional pair mechanism and promote the potential application in the new generation of the electronic devices based on oxide interfaces. In this project, we plan to fabricate perovskite oxide interfaces and modulate its superconducting properties by electrostatic and ferroelectric field effect. We will fabricate two types of superconducting heterointerfaces CaCuO2/SrTiO3 and LaAlO3/SrTiO3 by pulsed laser deposition method. With huge carrier modulation of electrostatic effect of ionic liquid gating technology, the tuning of superconducting properties of both interfaces will be conducted. Meanwhile, we plan to tailor the superconducting properties of CaCuO2/SrTiO3 and LaAlO3/SrTiO3 interface by applying environmentally friendly lead-free ferroelectric layer BaTiO3, respectively. With the aid of first-principles calculations as well the theory of condensed-matter physics, we try to make the well understanding of the nature of electron behaviors in oxide interfaces. Through these studies, we expect to shed some light on searching for novel high-temperature superconducting materials and provide significant insights into the potential application based on oxide interfaces.

钙钛矿氧化物异质界面因呈现出新奇而丰富的物理现象成为当今凝聚态物理学的研究热点之一。界面超导电性的研究和调控对帮助理解非常规超导机制、推动氧化物界面电子学的发展具有重大的意义。本项目拟进行钙钛矿氧化物界面异质的制备和超导电性调控研究，采用脉冲激光沉积技术制备超导的CaCuO2/SrTiO3和LaAlO3/SrTiO3异质界面、借助综合物性测量手段表征界面质量和超导性能，开展静电场和铁电极化场调控界面输运性质研究，结合第一性原理计算和凝聚态理论，深化对氧化物异质界面超导电性的形成机制和规律的理解。为寻找新型高温超导体系、研制新型复杂氧化物异质界面电子学器件进行积极的探索。

钙钛矿氧化物体系中具有较强的电子电荷、轨道、自旋以及晶格声子自由度间的耦合作用，这些自由度间强烈的相互影响在其异质界面结构中表现得尤为显著，故此我们可以简单地通过外场调控单一自由度，就可以在复杂氧化物异质界面体系中实现丰富的量子特性，从而实现全新的量子调控。本项目采用脉冲激光沉积技术制备了高质量的LaAlO3/SrTiO3异质结构、借助原子力显微镜和X射线衍射技术检查了异质结构的形貌和晶体结构，综合物性测量手段表征界面的电输运和磁性质，开展了表面覆盖BaTiO3铁电层的LaAlO3/SrTiO3异质界面制备和铁电场效应界面超导器件工艺研究。取得的主要研究结果如下：1) 获得了具有超导电性的LaAlO3/SrTiO3异质界面结构，超导转变温度为250 mK；2）发现LaAlO3/SrTiO3 界面结构中可能存在铁磁绝缘态的实验证据；3）开发出了满足载流子浓度和界面电导率测试需求的BaTiO3/LaAlO3/SrTiO3霍尔桥微加工工艺。这些研究成果将有助于深化对复杂氧化物异质界面体系中的电子运动行为的客观规律的认知，在今后实现全新的量子调控应用中奠定坚实科学基础。