Observation of anomalous phonon softening in bilayer graphene.
Observation of anomalous phonon softening in bilayer graphene.
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DOI：
10.1103/physrevlett.101.136804
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发表时间：
2007-12
影响因子：
8.6
通讯作者：
Jun Yan;E. Henriksen;P. Kim;A. Pinczuk
中科院分区：
文献类型：
--
作者：
Jun Yan;E. Henriksen;P. Kim;A. Pinczuk
电子空穴对与晶格振动的相互作用表现出许多有趣的物理现象，例如著名的科恩异常。在这里，我们报告了在双层石墨烯中观察到的不寻常的声子软化，这为另一种类型的声子异常提供了第一个实验证据。与科恩异常类似，科恩异常是声子群速度的对数奇点 [W.科恩，物理学家。莱特牧师。 2, 393 (1959)]，观察到的声子异常表现出光学声子能量的对数奇点。由于共振电子声子耦合效应，单层石墨烯中也出现了这种异常现象，尽管没有观察到。我们提出了为什么在双层样品中更容易观察的解释。
The interaction of electron-hole pairs with lattice vibrations exhibits a wealth of intriguing physical phenomena such as the renowned Kohn anomaly. Here we report the observation in bilayer graphene of an unusual phonon softening that provides the first experimental proof for another type of phonon anomaly. Similar to the Kohn anomaly, which is a logarithmic singularity in the phonon group velocity [W. Kohn, Phys. Rev. Lett. 2, 393 (1959)], the observed phonon anomaly exhibits a logarithmic singularity in the optical-phonon energy. Arising from a resonant electron-phonon coupling effect, the anomaly was also expected, albeit not observed, in monolayer graphene. We propose an explanation for why it is easier to observe in bilayer samples.