Dapolito Michael, Tsuneto Makoto, Zheng Wenjun, Wehmeier Lukas, Xu Suheng, Chen Xinzhong, Sun Jiacheng, Du Zengyi, Shao Yinming, Jing Ran, Zhang Shuai, Bercher Adrien, Dong Yinan, Halbertal Dorri, Ravindran Vibhu, Zhou Zijian, Petrovic Mila, Gozar Adrian, Carr G L, Li Qiang, Kuzmenko Alexey B, Fogler Michael M, Basov D N, Du Xu, Liu Mengkun
Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, USA.
Department of Physics, Columbia University, New York, NY, USA.
Nat Nanotechnol. 2023 Dec;18(12):1409-1415. doi: 10.1038/s41565-023-01488-y. Epub 2023 Aug 21.
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.
磁场会对量子材料中的电子运动产生深远影响。预计处于强磁场中的二维电子系统会表现出量子化的霍尔电导率、手性边缘电流以及被称为磁等离子体激元和磁激子的独特集体模式。迄今为止，在电荷中性样品中产生这些传播的集体模式并在其原生纳米长度尺度上对其进行成像在实验上一直难以实现。在这里，我们在其原生长度尺度上可视化传播的磁激子极化激元，并报告它们在近电荷中性石墨烯中的磁场可调色散。对这些集体模式及其相关的纳米电光响应进行成像，使我们能够识别样品边缘处极化激元调制的光学和光热电效应，这些效应在电荷中性附近最为明显。我们的工作得益于低温近场光学显微镜技术的创新，该技术能够对二维材料在高达7 T磁场下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通过利用高磁场来探索和操纵低载流子掺杂样品中的磁极化激元。
