Laboratory for Topological Quantum Matter and Spectroscopy (B7), Department of Physics, Princeton University, Princeton, NJ 08544, USA.
Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ 08854 USA.
Sci Adv. 2017 Mar 24;3(3):e1501692. doi: 10.1126/sciadv.1501692. eCollection 2017 Mar.
Engineered lattices in condensed matter physics, such as cold-atom optical lattices or photonic crystals, can have properties that are fundamentally different from those of naturally occurring electronic crystals. We report a novel type of artificial quantum matter lattice. Our lattice is a multilayer heterostructure built from alternating thin films of topological and trivial insulators. Each interface within the heterostructure hosts a set of topologically protected interface states, and by making the layers sufficiently thin, we demonstrate for the first time a hybridization of interface states across layers. In this way, our heterostructure forms an emergent atomic chain, where the interfaces act as lattice sites and the interface states act as atomic orbitals, as seen from our measurements by angle-resolved photoemission spectroscopy. By changing the composition of the heterostructure, we can directly control hopping between lattice sites. We realize a topological and a trivial phase in our superlattice band structure. We argue that the superlattice may be characterized in a significant way by a one-dimensional topological invariant, closely related to the invariant of the Su-Schrieffer-Heeger model. Our topological insulator heterostructure demonstrates a novel experimental platform where we can engineer band structures by directly controlling how electrons hop between lattice sites.
凝聚态物理中的工程晶格，如冷原子光学晶格或光子晶体，可以具有与自然发生的电子晶体根本不同的性质。我们报告了一种新型的人工量子物质晶格。我们的晶格是由拓扑和非拓扑绝缘体交替的薄膜构成的多层异质结构。异质结构中的每个界面都有一组拓扑保护的界面态，通过使层足够薄，我们首次展示了界面态在层间的杂交。通过这种方式，我们的异质结构形成了一个新兴的原子链，其中界面充当晶格位置，界面态充当原子轨道，正如我们通过角分辨光发射光谱测量所看到的那样。通过改变异质结构的组成，我们可以直接控制晶格位置之间的跃迁。我们在超晶格能带结构中实现了拓扑和非拓扑相。我们认为，超晶格的能带结构可以通过一个与 Su-Schrieffer-Heeger 模型的不变量密切相关的一维拓扑不变量来显著地描述。我们的拓扑绝缘体异质结构展示了一个新的实验平台，我们可以通过直接控制电子在晶格位置之间的跃迁方式来设计能带结构。
