Hsu C-C, Teague M L, Wang J-Q, Yeh N-C
Department of Physics, California Institute of Technology, Pasadena, CA 91125, USA.
Kavli Nanoscience Institute, California Institute of Technology, Pasadena, CA 91125, USA.
Sci Adv. 2020 May 8;6(19):eaat9488. doi: 10.1126/sciadv.aat9488. eCollection 2020 May.
The existence of nontrivial Berry phases associated with two inequivalent valleys in graphene provides interesting opportunities for investigating the valley-projected topological states. Examples of such studies include observation of anomalous quantum Hall effect in monolayer graphene, demonstration of topological zero modes in "molecular graphene" assembled by scanning tunneling microscopy, and detection of topological valley transport either in graphene superlattices or at bilayer graphene domain walls. However, all aforementioned experiments involved nonscalable approaches of either mechanically exfoliated flakes or atom-by-atom constructions. Here, we report an approach to manipulating the topological states in monolayer graphene via nanoscale strain engineering at room temperature. By placing strain-free monolayer graphene on architected nanostructures to induce global inversion symmetry breaking, we demonstrate the development of giant pseudo-magnetic fields (up to ~800 T), valley polarization, and periodic one-dimensional topological channels for protected propagation of chiral modes in strained graphene, thus paving a pathway toward scalable graphene-based valleytronics.
与石墨烯中两个不等价谷相关的非平凡贝里相位的存在为研究谷投影拓扑态提供了有趣的机会。此类研究的例子包括在单层石墨烯中观测反常量子霍尔效应、通过扫描隧道显微镜组装的“分子石墨烯”中拓扑零模式的证明，以及在石墨烯超晶格或双层石墨烯畴壁中检测拓扑谷输运。然而，所有上述实验都涉及机械剥离薄片或逐个原子构建等不可扩展的方法。在此，我们报告一种在室温下通过纳米尺度应变工程操纵单层石墨烯中拓扑态的方法。通过将无应变的单层石墨烯放置在精心设计的纳米结构上以诱导全局反演对称性破缺，我们展示了巨大的赝磁场（高达约800 T）、谷极化以及用于手性模式在应变石墨烯中受保护传播的周期性一维拓扑通道的形成，从而为基于石墨烯的可扩展谷电子学铺平了道路。
