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arXiv 1102.3032cond-mat.mes-hallcond-mat.dis-nn
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具有结构化外电势的石墨烯纳米带的能隙

Energy gap in graphene nanoribbons with structured external electric potentials

W. Apel, G. Pal, L. Schweitzer

摘要:

研究了石墨烯锯齿形纳米带的电子性质。利用狄拉克-费米子方法,我们计算了无限长的纳米线的有限宽度$w$,终止于Dirichlet边界条件在横向上的能谱。我们表明,一个结构化的外部电位,作用于带的边缘区域内,可以诱导光谱间隙,从而开关的nanoriginates从金属绝缘行为。这种效应的基本机制是外部电势对自旋波函数的选择性影响,自旋波函数本质上是拓扑的,并且沿着石墨烯纳米颗粒的边界定位。在该单粒子描述中,可获得的最大能隙是$E_{\rm max}\propto π\hbar v_{\rm F}/w$,即,对于$w=$ 15 nm,$\approx 0.12$ \,eV。在紧束缚晶格模型下,数值研究了边缘无序对能隙的稳定性以及无序对双端电导的影响。我们发现,能隙持续,只要施加的外部有效电位大于$\simeq 0.55\times W$,其中$W$是一个衡量的无序强度。我们认为,即使在没有光谱间隙的情况下,也存在由于局域化效应引起的传输间隙。

英文摘要:

The electronic properties of graphene zig-zag nanoribbons with electrostatic potentials along the edges are investigated. Using the Dirac-fermion approach, we calculate the energy spectrum of an infinitely long nanoribbon of finite width $w$, terminated by Dirichlet boundary conditions in the transverse direction. We show that a structured external potential that acts within the edge regions of the ribbon, can induce a spectral gap and thus switches the nanoribbon from metallic to insulating behavior. The basic mechanism of this effect is the selective influence of the external potentials on the spinorial wavefunctions that are topological in nature and localized along the boundary of the graphene nanoribbon. Within this single particle description, the maximal obtainable energy gap is $E_{\rm max}\propto π\hbar v_{\rm F}/w$, i.e., $\approx 0.12$\,eV for $w=$15\,nm. The stability of the spectral gap against edge disorder and the effect of disorder on the two-terminal conductance is studied numerically within a tight-binding lattice model. We find that the energy gap persists as long as the applied external effective potential is larger than $\simeq 0.55\times W$, where $W$ is a measure of the disorder strength. We argue that there is a transport gap due to localization effects even in the absence of a spectral gap.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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