衬底轨道滤波效应实现大拓扑能带反转的超平铋烯外延生长
Epitaxial Growth of Ultraflat Bismuthene with Large Topological Band Inversion Enabled by Substrate-Orbital-Filtering Effect
摘要：
量子自旋霍尔（QSH）系统有望成为低功耗的自旋电子器件，但其实际应用受到小能隙的极大阻碍。特别是在设计原则的指导下，制备大间隙QSH材料，无论是在科学研究还是实际应用中都是必不可少的。在这里，我们证明了大的原子自旋轨道耦合可以直接利用通过有趣的衬底轨道过滤效应，以产生大的能隙QSH系统，并在Ag（111）上外延合成的超平铋实验实现。理论计算表明，底层衬底选择性地过滤Bi pz轨道远离费米能级，导致具有非零磁量子数的pxy轨道，导致在K点处的约1 eV的大拓扑带隙。通过扫描隧道光谱结合密度泛函理论计算确定了相应的拓扑边缘态。我们的研究结果提供了一般策略来设计大能隙QSH系统，并进一步探索其拓扑相关的物理。
英文摘要：
Quantum spin Hall (QSH) systems hold promises of low-power-consuming spintronic devices, yet their practical applications are extremely impeded by the small energy gaps. Fabricating QSH materials with large gaps, especially under the guidance of design principles, is essential for both scientific research and practical applications. Here, we demonstrate that large on-site atomic spin-orbit coupling can be directly exploited via the intriguing substrate-orbital-filtering effect to generate large-gap QSH systems and experimentally realized on the epitaxially synthesized ultraflat bismuthene on Ag(111). Theoretical calculations reveal that the underlying substrate selectively filters Bi pz orbitals away from the Fermi level, leading pxy orbitals with nonzero magnetic quantum numbers, resulting in large topological gap of ~1 eV at the K point. The corresponding topological edge states are identified through scanning tunneling spectroscopy combined with density functional theory calculations. Our findings provide general strategies to design large-gap QSH systems and further explore their topology-related physics.
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