Wang Feng, Zhang Yuanbo, Tian Chuanshan, Girit Caglar, Zettl Alex, Crommie Michael, Shen Y Ron
Department of Physics, University of California at Berkeley, Berkeley, CA 94720, USA.
Science. 2008 Apr 11;320(5873):206-9. doi: 10.1126/science.1152793. Epub 2008 Mar 13.
Two-dimensional graphene monolayers and bilayers exhibit fascinating electrical transport behaviors. Using infrared spectroscopy, we find that they also have strong interband transitions and that their optical transitions can be substantially modified through electrical gating, much like electrical transport in field-effect transistors. This gate dependence of interband transitions adds a valuable dimension for optically probing graphene band structure. For a graphene monolayer, it yields directly the linear band dispersion of Dirac fermions, whereas in a bilayer, it reveals a dominating van Hove singularity arising from interlayer coupling. The strong and layer-dependent optical transitions of graphene and the tunability by simple electrical gating hold promise for new applications in infrared optics and optoelectronics.
二维石墨烯单分子层和双分子层展现出迷人的电输运行为。通过红外光谱，我们发现它们还具有强烈的带间跃迁，并且其光学跃迁可通过电门控得到显著改变，这与场效应晶体管中的电输运非常相似。带间跃迁的这种门控依赖性为光学探测石墨烯能带结构增添了一个有价值的维度。对于石墨烯单分子层，它直接产生狄拉克费米子的线性能带色散，而在双分子层中，它揭示了由层间耦合产生的主导范霍夫奇点。石墨烯强烈且依赖于层数的光学跃迁以及通过简单电门控实现的可调性为红外光学和光电子学的新应用带来了希望。
