二维Su-Schrieffer-Heeger晶格中带隙Dirac锥的观察
Observation of Gapped Dirac Cones in a Two-Dimensional Su-Schrieffer-Heeger Lattice
摘要：
二维矩形晶格中的Su-Schrieffer-Heeger（SSH）模型具有沿特定外围具有拓扑边缘状态的无隙或有隙狄拉克锥。虽然这种简单的模型最近已经在光子/声学晶格和电路中实现，但其在凝聚态系统中的物质实现仍然缺乏。本文利用角分辨光电子能谱和理论计算研究了Ag（001）衬底上矩形Si晶格的原子和电子结构。我们证明了Si晶格在布里渊区拐角处有带隙的狄拉克锥。我们的紧束缚分析表明，狄拉克带可以用一个具有各向异性极化的二维SSH模型来描述。狄拉克锥的能隙由一个方向上的交替跳跃振幅和另一个方向上的交错势能驱动，并具有拓扑边缘态。我们的结果建立了一个理想的平台，探索丰富的物理性质的二维SSH模型。
英文摘要：
The Su-Schrieffer-Heeger (SSH) model in a two-dimensional rectangular lattice features gapless or gapped Dirac cones with topological edge states along specific peripheries. While such a simple model has been recently realized in photonic/acoustic lattices and electric circuits, its material realization in condensed matter systems is still lacking. Here, we study the atomic and electronic structure of a rectangular Si lattice on Ag(001) by angle-resolved photoemission spectroscopy and theoretical calculations. We demonstrate that the Si lattice hosts gapped Dirac cones at the Brillouin zone corners. Our tight-binding analysis reveals that the Dirac bands can be described by a 2D SSH model with anisotropic polarizations. The gap of the Dirac cone is driven by alternative hopping amplitudes in one direction and staggered potential energies in the other one and hosts topological edge states. Our results establish an ideal platform to explore the rich physical properties of the 2D SSH model.
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