Infrared nano-imaging of Dirac magnetoexcitons in graphene
Infrared nano-imaging of Dirac magnetoexcitons in graphene
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DOI：
10.1038/s41565-023-01488-y
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发表时间：
2023-08-21
影响因子：
38.3
通讯作者：
Liu, Mengkun
中科院分区：
文献类型：
--
作者：
Dapolito, Michael;Tsuneto, Makoto;Liu, Mengkun
磁场可以对量子材料中电子的运动产生深远的影响。二维电子系统受到强磁场的预期表现出量子化霍尔电导率，手性边缘电流和独特的集体模式称为磁等离子体和磁激子。在电荷中性的样品中产生这些传播的集体模式，并在它们的原生纳米长度尺度上对它们进行成像，迄今为止在实验上是难以捉摸的。在这里，我们可视化传播磁激子极化激元在其原生的长度尺度，并报告其磁场可调分散在近电荷中性石墨烯。成像这些集体模式及其相关的纳米电光响应，使我们能够识别极化激元调制的光学和光热电效应在样品的边缘，这是最明显的近电荷中性。我们的工作是通过低温近场光学显微镜技术的创新实现的，该技术允许在高达7 T的磁场下对二维材料的近场响应进行纳米成像。这种纳米磁光学方法使我们能够探索和操纵样品中的磁极化子与低载流子掺杂通过利用高磁场。狄拉克磁激子与非平凡的纳米电动力学形成的朗道水平的激发电荷中性石墨烯。在这里，狄拉克磁激子色散直接成像高达7 T通过磁低温近场显微镜。
Magnetic fields can have profound effects on the motion of electrons in quantum materials. Two-dimensional electron systems subject to strong magnetic fields are expected to exhibit quantized Hall conductivity, chiral edge currents and distinctive collective modes referred to as magnetoplasmons and magnetoexcitons. Generating these propagating collective modes in charge-neutral samples and imaging them at their native nanometre length scales have thus far been experimentally elusive. Here we visualize propagating magnetoexciton polaritons at their native length scales and report their magnetic-field-tunable dispersion in near-charge-neutral graphene. Imaging these collective modes and their associated nano-electro-optical responses allows us to identify polariton-modulated optical and photo-thermal electric effects at the sample edges, which are the most pronounced near charge neutrality. Our work is enabled by innovations in cryogenic near-field optical microscopy techniques that allow for the nano-imaging of the near-field responses of two-dimensional materials under magnetic fields up to 7 T. This nano-magneto-optics approach allows us to explore and manipulate magnetopolaritons in specimens with low carrier doping via harnessing high magnetic fields.Dirac magnetoexcitons with non-trivial nanoscale electrodynamics are formed from the excitation of Landau levels in charge-neutral graphene. Here, the Dirac magnetoexciton dispersion is directly imaged up to 7 T via a magneto cryogenic near-field microscope.