Kavli Institute of Nanoscience, Delft University of Technology, Delft, the Netherlands.
Max Planck Institute for Chemical Physics of Solids, Dresden, Germany.
Nat Mater. 2023 May;22(5):576-582. doi: 10.1038/s41563-023-01498-0. Epub 2023 Mar 16.
Quantum materials can display physical phenomena rooted in the geometry of electronic wavefunctions. The corresponding geometric tensor is characterized by an emergent field known as the Berry curvature (BC). Large BCs typically arise when electronic states with different spin, orbital or sublattice quantum numbers hybridize at finite crystal momentum. In all the materials known to date, the BC is triggered by the hybridization of a single type of quantum number. Here we report the discovery of the first material system having both spin- and orbital-sourced BC: LaAlO/SrTiO interfaces grown along the [111] direction. We independently detect these two sources and probe the BC associated to the spin quantum number through the measurements of an anomalous planar Hall effect. The observation of a nonlinear Hall effect with time-reversal symmetry signals large orbital-mediated BC dipoles. The coexistence of different forms of BC enables the combination of spintronic and optoelectronic functionalities in a single material.
量子材料可以表现出源于电子波函数几何结构的物理现象。相应的几何张量的特征是出现了一种被称为 Berry 曲率（BC）的外场。当具有不同自旋、轨道或次晶格量子数的电子态在有限晶体动量处杂化时，通常会产生大的 BC。在迄今为止已知的所有材料中，BC 是由单一类型量子数的杂化引发的。在这里，我们报告了第一个具有自旋和轨道源 BC 的材料系统的发现：沿 [111] 方向生长的 LaAlO/SrTiO 界面。我们独立地检测到这两个来源，并通过对反常平面霍尔效应的测量来探测与自旋量子数相关的 BC。具有时间反演对称性的非线性霍尔效应的观测表明存在大的轨道介导 BC 偶极子。不同形式的 BC 的共存使得在单个材料中组合 spintronic 和光电功能成为可能。
