悬浮石墨烯纳米收缩体的量子化电导
Quantized conductance of a suspended graphene nanoconstriction
摘要：
石墨烯电子学中尚未探索的领域是通过石墨烯纳米结构的量子弹道输运领域。高迁移率石墨烯制备的最新进展有望导致该领域许多新的量子力学效应的实验验证和/或发现。示例是由于特定石墨烯边缘的影响，例如石墨烯纳米管的锯齿形边缘处的自旋极化以及石墨烯谷电子学领域中谷自由度的使用8。作为这个方向的第一步，我们提出了在零磁场和4.2 K温度下，在高迁移率悬浮石墨烯弹道纳米收缩中，在2e^2/h的整数倍处观察量子化电导。这种量子化在高于60 mT的磁场下演化为石墨烯的典型量子霍尔效应。电压偏置光谱揭示了前两个子带之间的能量间隔为8毫电子伏。在低至~0.2T的磁场下，在0.6 2e^2/h处出现的显著特征类似于在GaAs-AlGaAs二维电子气中量子点接触中观察到的“0.7异常”，可能起源于电子-电子相互作用。
英文摘要：
A yet unexplored area in graphene electronics is the field of quantum ballistic transport through graphene nanostructures. Recent developments in the preparation of high mobility graphene are expected to lead to the experimental verification and/or discovery of many new quantum mechanical effects in this field. Examples are effects due to specific graphene edges, such as spin polarization at zigzag edges of a graphene nanoribbon and the use of the valley degree of freedom in the field of graphene valleytronics8. As a first step in this direction we present the observation of quantized conductance at integer multiples of 2e^2/h at zero magnetic field and 4.2 K temperature in a high mobility suspended graphene ballistic nanoconstriction. This quantization evolves into the typical quantum Hall effect for graphene at magnetic fields above 60mT. Voltage bias spectroscopy reveals an energy spacing of 8 meV between the first two subbands. A pronounced feature at 0.6 2e^2/h present at a magnetic field as low as ~0.2T resembles the "0.7 anomaly" observed in quantum point contacts in a GaAs-AlGaAs two dimensional electron gas, having a possible origin in electron-electron interactions.
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