Observation of a universal donor-dependent vibrational mode in graphene
Observation of a universal donor-dependent vibrational mode in graphene
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DOI：
10.1038/ncomms4257
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发表时间：
2014-02-01
影响因子：
16.6
通讯作者：
Gruneis, A.
中科院分区：
文献类型：
--
作者：
Fedorov, A. V.;Verbitskiy, N. I.;Gruneis, A.
插层石墨中的电声耦合和超导电性的出现已经得到了广泛的研究。然而，在这些材料的2D等效材料中，从未观察到声子介导的超导电性，即掺杂单层石墨烯。在这里，我们进行角度分辨光电子能谱，试图找到一个石墨烯的电子给体，能够诱导强烈的电子-声子耦合和超导。我们研究了电子给体Cs、Rb、K、Na、Li、Ca，并根据光谱函数确定了它们的全电子能带结构、Eliashberg函数和超导临界温度T-c。所有的掺杂剂都出现了一个意想不到的低能峰，其能量和强度取决于掺杂剂原子。我们证明了这个峰值是与掺杂剂相关的振动的结果。这一峰的低能量和高强度对于实现超导性至关重要，其中钙是实现石墨烯超导性的最有希望的候选者。
Electron-phonon coupling and the emergence of superconductivity in intercalated graphite have been studied extensively. Yet, phonon-mediated superconductivity has never been observed in the 2D equivalent of these materials, doped monolayer graphene. Here we perform angle-resolved photoemission spectroscopy to try to find an electron donor for graphene that is capable of inducing strong electron-phonon coupling and superconductivity. We examine the electron donor species Cs, Rb, K, Na, Li, Ca and for each we determine the full electronic band structure, the Eliashberg function and the superconducting critical temperature T-c from the spectral function. An unexpected low-energy peak appears for all dopants with an energy and intensity that depend on the dopant atom. We show that this peak is the result of a dopant-related vibration. The low energy and high intensity of this peak are crucially important for achieving superconductivity, with Ca being the most promising candidate for realizing superconductivity in graphene.