Novel Phases of Transition-Metal Oxides in Heterostructured and Superoxygenated Thin Films

异质结构和超氧化薄膜中过渡金属氧化物的新相

• 批准号: RGPIN-2020-06830
• 负责人: Wei, John
• 金额: $ 1.75万
• 依托单位: University of Toronto
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=718175
• 关键词: Novel; Phases; Transition; Metal; Oxides

Transition--metal oxides (TMOs) have been a wellspring of quantum--ordered electronic phenomena, ranging from high critical-temperature (Tc) superconductivity to colossal magnetoresistance and multiferroism. This wide range of phenomena reflects the complex interplay among various types of electronic order. The high sensitivity of this interplay to chemical doping, lattice strain and electromagnetic fields produces rich electronic phase diagrams. Recent advances in epitaxial growth of oxide thin films have enabled different TMOs with perovskite--based crystal structures to be combined into heterostructures with atomically--sharp interfaces. This "Legoland" approach to oxide synthesis allows the interplay between different electronic phases from different TMOs to be tuned by varying the chemical makeup, length scale and lattice strain of each consitutent oxide. More recently, atomic--scale electron microscopy and spectroscopy studies have observed intergrowths of exotic structural phases in several TMO heterostructures and in thin films annealed in ultrahigh-pressure oxygen. The formation of these exotic TMO phases is attributed to either heteroepitaxial strain or to enhanced oxidation, indicating that the thermodynamic phase stability of TMO thin films is vastly different than in bulk materials. Guided by these new paradigms, my proposed research aims to generate and to detect novel electronic and structural phases of TMOs in heterostructured and superoxygenated thin films. The materials I will focus on are cuprates, manganites, nickelates, ruthenates and iridates, the latter having strong spin--orbit coupling that is crucial for the formation of topological electronic phases. Multilayer and unilayer thin films will be grown using pulsed laser deposition, and characterized by electrical transport, x-ray diffraction and x--ray absorption spectroscopy. To identify the novel TMO phases, several atomic--scale microscopy and spectroscopy probes will also be used: 1) scanning transmission electron microscopy; 2) electron energy-loss spectroscopy; 3) d-wave Andreev reflection spectroscopy; 4) scanning tunneling spectroscopy. My general goals are: 1) to discover novel TMO phases with enhanced lattice complexity and electronic properties by by--passing known thermodynamic limitations; and 2) to realize exotic interfacial and hybrid phenomena by heterostructurally integrating known phases of TMOs. For the superoxygenation projects, a central objective is to further raise the Tc of cuprates by further increasing their lattice complexity. For the heterostructure projects, a major milestone is to achieve spin--triplet and topological superconductivity using the proximity effect. Successful generation and detection of these novel TMO phases and phenomena will enable them to be harnessed for quantum electronic devices, particularly in the emerging field of superconducting spintronics as well as strain--based and topology--based electronics.

过渡金属氧化物（TMOs）一直是量子有序电子现象的源泉，从高临界温度（Tc）超导性到巨磁电阻和多铁性。这种广泛的现象反映了各种类型的电子秩序之间复杂的相互作用。这种相互作用对化学掺杂、晶格应变和电磁场的高灵敏度产生了丰富的电子相图。