Efficient Fizeau drag from Dirac electrons in monolayer graphene
Efficient Fizeau drag from Dirac electrons in monolayer graphene
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DOI：
10.1038/s41586-021-03574-4
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发表时间：
2021-06
期刊：
影响因子：
64.8
通讯作者：
Wenyu Zhao;Sihan Zhao;Hongyuan Li;Sheng Wang;Shaoxin Wang;M. Iqbal Bakti Utama;S. Kahn;Yue Jiang;Xiao Xiao-Xiao;SeokJae Yoo;Kenji Watanabe;T. Taniguchi;A. Zettl;Feng Wang
中科院分区：
文献类型：
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作者：
Wenyu Zhao;Sihan Zhao;Hongyuan Li;Sheng Wang;Shaoxin Wang;M. Iqbal Bakti Utama;S. Kahn;Yue Jiang;Xiao Xiao-Xiao;SeokJae Yoo;Kenji Watanabe;T. Taniguchi;A. Zettl;Feng Wang
菲索在1850年证明了当光在运动介质中传播时，它的速度是可以改变的。然而，这种对光速的控制还不能有效地通过通过电流的快速移动的电子介质来实现。由于电子与光之间的强电磁耦合导致等离子体激元的集体激发，因此假设电子流系统中的菲索阻力表现为等离子体多普勒效应。电子系统中等离子体多普勒效应的实验观测一直是一个挑战，因为等离子体的传播速度远远快于传统贵金属中的电子漂移速度。在这里，我们报告了通过利用高电子迁移率和无质量狄拉克电子的慢等离子体传播，在强偏态单层石墨烯中直接观察到等离子体极化子的菲索阻力。石墨烯中的大偏置电流产生了承载等离子激元极化子的快速漂移狄拉克电子介质。这导致了非互反等离子体传播，其中等离子体与漂移的电子介质一起运动，以增强的速度传播。我们使用低温近场红外纳米显微镜测量多普勒位移等离子体波长，直接成像低温下偏置石墨烯中的等离子体极化模式。我们观察到，在顺电子介质运动的等离子体激元和逆电子介质运动的等离子体激元之间，等离子体激元的波长差高达3.6%。我们关于等离子体多普勒效应的发现为非平衡系统中非互易表面等离子体激元的电控制提供了机会。
Fizeau demonstrated in 1850 that the speed of light can be modified when it is propagating in moving media. However, such control of the light speed has not been achieved efficiently with a fast-moving electron media by passing an electrical current. Because the strong electromagnetic coupling between the electron and light leads to the collective excitation of plasmon polaritons, it is hypothesized that Fizeau drag in electron flow systems manifests as a plasmonic Doppler effect. Experimental observation of the plasmonic Doppler effect in electronic systems has been challenge because the plasmon propagation speed is much faster than the electron drift velocity in conventional noble metals. Here we report direct observation of Fizeau drag of plasmon polaritons in strongly biased monolayer graphene by exploiting the high electron mobility and the slow plasmon propagation of massless Dirac electrons. The large bias current in graphene creates a fast-drifting Dirac electron medium hosting the plasmon polariton. This results in non-reciprocal plasmon propagation, where plasmons moving with the drifting electron media propagate at an enhanced speed. We measure the Doppler-shifted plasmon wavelength using cryogenic near-field infrared nanoscopy, which directly images the plasmon polariton mode in the biased graphene at low temperature. We observe a plasmon wavelength difference of up to 3.6 per cent between a plasmon moving with and a plasmon moving against the drifting electron media. Our findings on the plasmonic Doppler effect provide opportunities for electrical control of non-reciprocal surface plasmon polaritons in non-equilibrium systems.