Graduate Institute of Applied Physics, National Taiwan University, Taipei 106, Taiwan.
Nanoscale Res Lett. 2013 Aug 22;8(1):360. doi: 10.1186/1556-276X-8-360.
We have performed magnetotransport measurements on multilayer epitaxial graphene. By increasing the driving current I through our graphene devices while keeping the bath temperature fixed, we are able to study Dirac fermion heating and current scaling in such devices. Using zero-field resistivity as a self thermometer, we are able to determine the effective Dirac fermion temperature (TDF) at various driving currents. At zero field, it is found that TDF ∝ I≈1/2. Such results are consistent with electron heating in conventional two-dimensional systems in the plateau-plateau transition regime. With increasing magnetic field B, we observe an I-independent point in the measured longitudinal resistivity ρxx which is equivalent to the direct insulator-quantum Hall (I-QH) transition characterized by a temperature-independent point in ρxx. Together with recent experimental evidence for direct I-QH transition, our new data suggest that such a transition is a universal effect in graphene, albeit further studies are required to obtain a thorough understanding of such an effect.
我们对多层外延石墨烯进行了磁输运测量。通过在保持浴温不变的情况下增加通过石墨烯器件的驱动电流 I，我们能够研究这些器件中的狄拉克费米子加热和电流缩放。使用零场电阻率作为自温度计，我们能够确定在不同驱动电流下的有效狄拉克费米子温度（TDF）。在零场时，发现 TDF∝I≈1/2。这些结果与传统二维系统中在平台-平台过渡区的电子加热一致。随着磁场 B 的增加，我们观察到测量的纵向电阻率 ρxx 中存在一个与 I 无关的点，这相当于具有 ρxx 中与温度无关的点的直接绝缘-量子霍尔（I-QH）转变。结合最近关于直接 I-QH 转变的实验证据，我们的新数据表明，这种转变是石墨烯中的一种普遍现象，尽管需要进一步的研究来全面理解这种效应。
