清华大学材料科学与工程研究院《材料科学论坛》学术报告

报告题目：Microscopic manipulations of the electron correlation and topological properties in SrRuO3 ultrathin films

报告人：王凌飞博士（首尔国立大学研究助理教授）

报告时间：2019年12月30日（周一） 下午3点

报告地点：清华大学逸夫技术科学楼A205学术报告厅

联系人：王轲老师

欢迎广大师生踊跃参加！

报告摘要：

Perovskite-structured SrRuO3 is a prototypical ferromagnetic metal with a Curie temperature of ~ 160 K. Because of its high electrical conductivity and structural stability, SRO epitaxial film has been widely used as an electrode layer for perovskite oxide-based heterostructures and devices.1 Furthermore, a fine balance between the electron-electron correlation and spin-orbit coupling in SrRuO3 gives rise to a variety of exotic physical properties, including itinerant ferromagnetism, non-Fermi liquid electrical transport, magnetic monopoles in momentum space, and tunable magnetic skyrmions.[1]
Here, we will show our recent results about manipulating electron correlation and topological properties in SrRuO3 ultrathin films. In the first part, we will report the discovery of ferroelectrically tunable skyrmions in ultrathin BaTiO3/SrRuO3 bilayer heterostructures.[2] Ferroelectric proximity effect at the heterointerface can trigger a sizable Dzyaloshinskii-Moriya interaction (DMI), thus stabilizing magnetic skyrmions of ~100 nm in diameter. Thanks to the strong coupling between ferroelectric distortion and DMI, we achieved local, switchable, and nonvolatile control of both skyrmion density and stability. In the second part, we will focus on the highly tunable anomalous Hall effect (AHE) in SrRuO3 single layers. By harnessing the step-flow growth of SrRuO3 films, we induced a microscopically-ordered stripe pattern with one-unit-cell differences in film thickness. The associated spatial distribution of momentum-space Berry curvatures enables a unique two-channel AHE. The microscopic fingerprints of the two-channel AHE and skyrmion-induced topological Hall effect were also probed and identified via magnetic force microscopy. At last, we will exploit an atomic-scale metal-insulator transition triggered by surface termination conversion in SrRuO3 ultrathin films. We developed a uniform and effective termination engineering at the SrRuO3(001) surface via a simple water-leaching process. As the surface termination converts from SrO to RuO2, a highly insulating and non-ferromagnetic phase emerges within the topmost SrRuO3 monolayer.[3] These works may offer new paradigms to stimulate and tune exotic functionalities of oxide heterostructures at the microscale.

References:
[1]   Koster, G. et al. Review of Modern Physics, 84, 253 (2012).
[2]   Wang, L. et al. Nature Materials, 17, 1087 (2018).
[3]   Lee, H. -G. et al. Adv.Mater. 1905815 (2019)
 

王凌飞 个人简历：
2008至2013年于中国科学技术大学获凝聚态物理博士学位；
2013至2015年于阿卜杜拉国王科技大学从事博士后研究；
2015至2017年于首尔国立大学从事博士后研究；
2018至今于首尔国立大学担任研究助理教授。

研究方向：
从事氧化物薄膜、异质结和原型器件相关工作，2008年至今以第一作者和通讯作者在Nature Materials、Advanced Materials、Nano letters 等期刊发表文章二十余篇，个人被引超过1400次，H因子17。