Nonadiabatic Kohn anomaly in a doped graphene monolayer
Nonadiabatic Kohn anomaly in a doped graphene monolayer
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DOI：
10.1103/physrevlett.97.266407
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发表时间：
2006-12-31
影响因子：
8.6
通讯作者：
Mauri, Francesco
中科院分区：
文献类型：
--
作者：
Lazzeri, Michele;Mauri, Francesco
我们计算，从第一性原理，作为电荷掺杂的函数的石墨烯的E-2g，伽马声子（拉曼G带）的频率。计算使用（i）绝热Born-Oppenheimer近似和（ii）含时微扰理论，以探索超出此近似的动力学效应。这两种方法提供了非常不同的结果。而绝热声子频率弱依赖于掺杂，动态的一个迅速变化，因为一个Kohn异常。绝热近似被认为在大多数材料中是有效的。在这里，我们表明掺杂的石墨烯是一个壮观的例子，这种近似悲惨地失败了。
We compute, from first principles, the frequency of the E-2g, Gamma phonon (Raman G band) of graphene, as a function of the charge doping. Calculations are done using (i) the adiabatic Born-Oppenheimer approximation and (ii) time-dependent perturbation theory to explore dynamic effects beyond this approximation. The two approaches provide very different results. While the adiabatic phonon frequency weakly depends on the doping, the dynamic one rapidly varies because of a Kohn anomaly. The adiabatic approximation is considered valid in most materials. Here, we show that doped graphene is a spectacular example where this approximation miserably fails.