Tunable excitons in bilayer graphene
Tunable excitons in bilayer graphene
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DOI：
10.1126/science.aam9175
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发表时间：
2017-11-17
期刊：
影响因子：
56.9
通讯作者：
McEuen, Paul L.
中科院分区：
文献类型：
--
作者：
Ju, Long;Wang, Lei;McEuen, Paul L.
激子是固体材料中电子和空穴的束缚态，在绝缘体和半导体的光学特性中起着关键作用。在这里，我们报告了利用六方氮化硼封装的高质量双层石墨烯光电流光谱观察双层石墨烯（BLG）中的激子。我们观察到两个突出的激子共振，具有窄的线宽，可在中红外到太赫兹范围内调谐。这些激子遵循与传统半导体不同的光学选择规则，并具有电子伪自旋圈数为2的特征。外部磁场诱导谷激子的大分裂，对应于g因子约为20。这些发现为探索电可调石墨烯系统中具有伪自旋结构的激子物理提供了机会。
Excitons, the bound states of an electron and a hole in a solid material, play a key role in the optical properties of insulators and semiconductors. Here, we report the observation of excitons in bilayer graphene (BLG) using photocurrent spectroscopy of high-quality BLG encapsulated in hexagonal boron nitride. We observed two prominent excitonic resonances with narrow line widths that are tunable from the mid-infrared to the terahertz range. These excitons obey optical selection rules distinct from those in conventional semiconductors and feature an electron pseudospin winding number of 2. An external magnetic field induces a large splitting of the valley excitons, corresponding to a g-factor of about 20. These findings open up opportunities to explore exciton physics with pseudospin texture in electrically tunable graphene systems.