Anisotropic behaviours of massless Dirac fermions in graphene under periodic potentials
Anisotropic behaviours of massless Dirac fermions in graphene under periodic potentials
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DOI：
10.1038/nphys890
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发表时间：
2008-03-01
期刊：
影响因子：
19.6
通讯作者：
Louie, Steven G.
中科院分区：
文献类型：
--
作者：
Park, Cheol-Hwan;Yang, Li;Louie, Steven G.
石墨烯的锥形价带和导带产生具有中微子样线性能量色散的电荷载流子，并在这些带相遇的狄拉克点附近表现出手性行为（1-6）。这些特性为新现象的出现和高性能电子器件的开发提供了令人兴奋的机会。然而，用石墨烯制造高质量的器件，通常涉及将其蚀刻成纳米级结构（7-10），已被证明具有挑战性。在这里，我们表明，通过适当图案化的修饰或石墨烯表面上的接触施加的周期性电位导致进一步的意想不到的和潜在有用的电荷载流子行为。由于它们的手性性质，电荷载流子通过这种石墨烯超晶格的传播是高度各向异性的，并且在极端情况下导致群速度在一个方向上降低到零，但在另一个方向上不变。此外，我们表明，石墨烯超晶格中的载流子种类（电子，空穴或开放轨道）的密度和类型对施加的电势非常敏感，并且可以通过改变费米能级来进一步调整它们。以及解决有关石墨烯的手性无质量狄拉克费米子如何在周期性势中传播的基本问题，我们的研究结果表明，从适当设计的周期性表面图案中构建石墨烯电子电路的可能性，而不需要切割或蚀刻。
Graphene's conical valence and conduction bands give rise to charge carriers that have neutrino-like linear energy dispersion and exhibit chiral behaviour near the Dirac points where these bands meet(1-6). Such characteristics offer exciting opportunities for the occurrence of new phenomena and the development of high performance electronic devices. Making high quality devices from graphene, which typically involves etching it into nanoscale structures(7-10), however, has proven challenging. Here we show that a periodic potential applied by suitably patterned modifications or contacts on graphene's surface leads to further unexpected and potentially useful charge carrier behaviour. Owing to their chiral nature, the propagation of charge carriers through such a graphene superlattice is highly anisotropic, and in extreme cases results in group velocities that are reduced to zero in one direction but are unchanged in another. Moreover, we show that the density and type of carrier species ( electron, hole or open orbit) in a graphene superlattice are extremely sensitive to the potential applied, and they may further be tuned by varying the Fermi level. As well as addressing fundamental questions about how the chiral massless Dirac fermions of graphene propagate in a periodic potential, our results suggest the possibility of building graphene electronic circuits from appropriately engineered periodic surface patterns, without the need for cutting or etching.