How Close Can One Approach the Dirac Point in Graphene Experimentally?
How Close Can One Approach the Dirac Point in Graphene Experimentally?
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DOI：
10.1021/nl301922d
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发表时间：
2012-09-01
期刊：
影响因子：
10.8
通讯作者：
Gorbachev, Roman V.
中科院分区：
文献类型：
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作者：
Mayorov, Alexander S.;Elias, Daniel C.;Gorbachev, Roman V.
对石墨烯作为模型系统感兴趣的理论家经常提出上述问题，特别是在相对论量子物理的背景下。我们通过描述载流子迁移率达到几个 10(6) cm(2) V-1 s(-1) 的悬浮器件中的电子传输以及在低于 5 mT 的场中发生朗道量子化来提供实验答案。观察到的电荷不均匀性低至约 10(8) cm(-2)，从而允许每个微米级器件具有少量电荷载流子的中性状态。在液氦温度以上，此类器件的电子特性是固有的，仅受热激发控制。这使得狄拉克点可以在 1 meV 内接近，这是当前由剩余电荷不均匀性设定的极限。低于 1 K 时没有观察到绝缘态的迹象，这确定了可能带隙的上限。
The above question is frequently asked by theorists who are interested in graphene as a model system, especially in context of relativistic quantum physics. We offer an experimental answer by describing electron transport in suspended devices with carrier mobilities of several 10(6) cm(2) V-1 s(-1) and with the onset of Landau quantization occurring in fields below 5 mT. The observed charge inhomogeneity is as low as approximate to 10(8) cm(-2), allowing a neutral state with a few charge carriers per entire micrometer-scale device. Above liquid helium temperatures, the electronic properties of such devices are intrinsic, being governed by thermal excitations only. This yields that the Dirac point can be approached within 1 meV, a limit currently set by the remaining charge inhomogeneity. No sign of an insulating state is observed down to 1 K, which establishes the upper limit on a possible bandgap.