强电子关联的镍基和银基超薄异质结的计算模拟和材料设计

Correlated-electron oxide heterostructures remain research focus of condensed matter physics and material physics in recent years, and they have great potential applications in microelectronics, data storage and sensor technology. Heterostructure interfaces often give rise to novel physical phenomena not exhibited by the bulk constituents, due to the rearrangement of charge, spins, orbitals, lattice and the resulting rebalancing of their mutual interactions. Thus interface can be exploited to modify electronic structure and to tailor novel properties and behaviors. Based on density functional theory, maximally-localized Wannier function method, and the state-of-the-art dynamical mean-field theory, the main research contents are included: 1) Tuning of structural confinement, deformation, chemical modification and spontaneous polarization on the electronic structures of Ni-based and Ag-based ultra-thin heterostructures. According to band characteristics around the Fermi level, we pick out the (001) heterostructures with potential superconductivity and the (111) heterostructures with abundant band topology. 2) For the elected typical heterostructure configurations, the reasonable low energy effective Hamiltonians are constructed, then many body calculation methods are used to study the influence of electron correlation on electronic structure, the Fermi surface and magnetic properties, in order to provide theoretical support for preparation of Ni-based and Ag-based heterostructures with superconductivity and d-band correlated topological phase. 3) In view of practical application, modulation of electric field on electronic structure of the Ni-based and Ag-based heterostructures are also studied.

关联电子氧化物异质结是凝聚态物理和材料物理近年来的研究热点，在微电子、数据存储和传感器技术等方面有很大的应用前景。界面周围电荷、自旋、轨道和晶格的重新组合，会修改费米面附近的电子结构，达到控制材料物理性质的目的，使异质结呈现出完全不同于体结构单元的新的物理相。联合密度泛函理论、最大局域化瓦尼尔函数方法和动力学平均场理论，我们拟研究的主要内容包括：1)研究结构受限、结构形变、化学组分修改、自发极化对镍基和银基超薄异质结电子结构的调控。基于费米面附近能带特征分别找出有超导潜力的(001)取向的异质结构型和有丰富d电子能带拓扑性质的(111)取向的异质结构型。2)对选出的代表性构型，合理构建出低能有效哈密顿，使用多体计算方法研究关联效应对电子结构、费米面和磁性的影响，为具备超导电性和d带关联拓扑相的异质结材料的制备提供理论支持。3)从应用的角度，研究外电场对镍基和银基超薄异质结电子结构的调制。

铜酸盐等高温超导体的发现引起了人们对其它过渡族金属复合材料超导电性的探索。因为镍和银都是元素周期表上铜的近邻元素，镍基或银基的关联电子氧化物异质结构成为凝聚态物理和材料物理近年来的研究热点。联合密度泛函理论、最大局域化瓦尼尔函数方法和多体计算方法，我们研究了结构受限、结构形变、化学组分修改、自发极化对镍基和银基超薄异质结电子结构的调控。基于费米面附近能带特征找出了有高温超导潜力和d电子能带拓扑特性的异质界面构型。对其中的代表性结构，构建出相应的p-d模型哈密顿，比较得到的紧束缚参数和铜酸盐超导材料的异同，从中寻找规律。最后，使用多体计算方法研究关联效应对电子结构、费米面和磁性的影响。我们的研究为具备超导电性和关联拓扑相的人工异质界面结构材料的制备提供理论支持。在理论模拟的同时，我们也积极地和强磁场实验团队开展相关材料物性的合作研究。目前在本项目资助下，团队在国际核心期刊上发表SCI论文8篇，另有2篇在投。