外场对拓扑相变氧化物薄膜物性的调控研究进展

Research progress of control of physical properties of topological phase change oxide films by external field

钙钛矿型过渡金属氧化物在外场激励下可以通过得失氧离子发生显著的结构拓扑相变,同时伴随着输运、磁性、光学等物性的巨大变化,是近年来被重点关注的研究体系,在固态氧化物燃料电池、氧气传感器、催化活性、智能光学窗口以及神经形态计算器件中具有巨大的应用前景.本工作回顾了近年来国内外研究小组在拓扑相变氧化物薄膜及其物性调控方面的工作进展,详细介绍了这类典型薄膜材料在应力场、电场、光场、温度场等外场激励下呈现出的新奇物性,并讨论了其基本物理机制.本综述旨在进一步认识此类材料中的电荷、晶格、轨道等量子序之间的微观耦合机制及其与宏观物性的关联,相关研究有望为基于功能氧化物的高灵敏度、弱场响应的电子器件提供新材料、新途径和新思路.

Perovskite transition-metal oxides can undergo significant structural topological phase transition between perovskite structure,brownmillerite structure,and infinite-layer structure under the external field through the gain and loss of the oxygen ions,accompanied with significant changes in physical properties such as transportation,magnetism,and optics.Topotactic phase transformation allows structural transition without losing the crystalline symmetry of the parental phase and provides an effective platform for utilizing the redox reaction and oxygen diffusion within transition metal oxides,and establishing great potential applications in solid oxide fuel cells,oxygen sensors,catalysis,intelligent optical windows,and neuromorphic devices.In this work,we review the recent research progress of manipulating the topological phase transition of the perovskitetype oxide films and regulating their physical properties,mainly focusing on tuning the novel physical properties of these typical films through strong interaction between the lattice and electronic degrees of freedom by the action of external fields such as strain,electric field,optical field,and temperature field.For example,a giant photoinduced structure distortion in SrCoO2.5 thin film excited by photons is observed to be higher than any previously reported results in the other transition metal oxide films.The SrFeO2 films undergo an insulatorto-metal transition when the strain state changes from compressive state to tensile state.It is directly observed that perovskite SrFeO3 nanofilament is formed under the action of electric field and extends almost through the brownmillerite SrFeO2.5 matrix in the ON state and is ruptured in the OFF state,unambiguously revealing a filamentary resistance switching mechanism.Utilizing in situ electrical scanning transmission electron microscopy,the transformation from brownmillerite SrFeO2.5 to infinite-layer SrFeO2 under electric field can be directly visualized with atomic resolution.We also clarify the relationship between the microscopic coupling mechanism and the macroscopic quantum properties of charges,lattices,orbits,spin,etc.Relevant research is expected to provide a platform for new materials,new approaches and new ideas for developing high-sensitivity and weak-field response electronic devices based on functional oxides.These findings about the topological phase transition in perovskite oxide films can expand the research scope of material science,and have important significance in exploring new states of matters and studying quantum critical phenomena.