Designer Dirac fermions and topological phases in molecular graphene
Designer Dirac fermions and topological phases in molecular graphene
复制标题
DOI：
10.1038/nature10941
复制
发表时间：
2012-03-15
期刊：
影响因子：
64.8
通讯作者：
Manoharan, Hari C.
中科院分区：
文献类型：
--
作者：
Gomes, Kenjiro K.;Mar, Warren;Manoharan, Hari C.
单层石墨烯中无质量狄拉克费米子的观察产生了一个新的科学和技术领域，寻求利用固态材料中相对论行为的电荷载流子（1）。在越来越多的狄拉克材料中，包括双层石墨烯、拓扑绝缘体的表面态和铁基高温超导体，都已经研究和提出了无质量和有质量的狄拉克费米子。由于这种物理学的可及性取决于新材料的合成，因此对狄拉克准粒子的探索已经扩展到人工系统，例如包含超冷原子的晶格（2-4）。在这里，我们报告了狄拉克费米子在一个完全可调的凝聚态系统中的出现-分子石墨烯-通过在铜表面的传统二维电子系统上对一氧化碳分子进行原子操作组装而成（5）。使用低温扫描隧道显微镜和光谱学，我们将二维狄拉克方程的对称性嵌入到电子晶格中，然后可视化和塑造所产生的基态。这些实验表明，系统中存在线性分散的无质量准粒子，并伴有石墨烯的态密度特征。然后，我们调整晶格位置之间的量子隧穿局部调整传播电子的相位增量。晶格扭曲的空间纹理产生原子级尖锐的p-n和p-n-p结器件，具有二维控制狄拉克费米子密度和赋予狄拉克粒子质量的能力（6-8）。此外，我们在局部和全局应用标量势和矢量势来产生拓扑上不同的基态，并最终产生嵌入规范场（9-12），其中狄拉克电子对存在于其参考系中但不存在于实验室系中的“伪”电场和磁场作出反应。我们证明了这些规范场产生的朗道能级可以达到相对论磁量子极限，这在天然石墨烯中是无法达到的。分子石墨烯提供了一种使用定制的纳米结构在凝聚态物质中合成奇异拓扑电子相的通用手段。
The observation of massless Dirac fermions in monolayer graphene has generated a new area of science and technology seeking to harness charge carriers that behave relativistically within solid-state materials(1). Both massless and massive Dirac fermions have been studied and proposed in a growing class of Dirac materials that includes bilayer graphene, surface states of topological insulators and iron-based high-temperature superconductors. Because the accessibility of this physics is predicated on the synthesis of new materials, the quest for Dirac quasi-particles has expanded to artificial systems such as lattices comprising ultracold atoms(2-4). Here we report the emergence of Dirac fermions in a fully tunable condensed-matter system-molecular graphene-assembled by atomic manipulation of carbon monoxide molecules over a conventional two-dimensional electron system at a copper surface(5). Using low-temperature scanning tunnelling microscopy and spectroscopy, we embed the symmetries underlying the two-dimensional Dirac equation into electron lattices, and then visualize and shape the resulting ground states. These experiments show the existence within the system of linearly dispersing, massless quasi-particles accompanied by a density of states characteristic of graphene. We then tune the quantum tunnelling between lattice sites locally to adjust the phase accrual of propagating electrons. Spatial texturing of lattice distortions produces atomically sharp p-n and p-n-p junction devices with two-dimensional control of Dirac fermion density and the power to endow Dirac particles with mass(6-8). Moreover, we apply scalar and vector potentials locally and globally to engender topologically distinct ground states and, ultimately, embedded gauge fields(9-12), wherein Dirac electrons react to 'pseudo' electric and magnetic fields present in their reference frame but absent from the laboratory frame. We demonstrate that Landau levels created by these gauge fields can be taken to the relativistic magnetic quantum limit, which has so far been inaccessible in natural graphene. Molecular graphene provides a versatile means of synthesizing exotic topological electronic phases in condensed matter using tailored nanostructures.