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arXiv 1702.07494cond-mat.mes-hallcond-mat.mtrl-sci
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石墨烯中热载流子的界面缺陷辅助声子散射

Interface defect-assisted phonon scattering of hot carriers in graphene

Sergey Menabde, Hyunwoo Cho, Namkyoo Park

摘要:

石墨烯的宽带和超快光响应近年来得到了广泛的研究,尽管光激发载流子动力学仍然远未完全理解。不同的实验方法意味着热电子的两种根本不同的散射机制之一。一种是高能光学声子,另一种是无序驱动的声学声子超碰撞。然而,通过光学和声学声子的并发弛豫尚未考虑到目前为止,阻碍了在一个统一的框架内解释不同的实验。在这里,我们扩大了光学声子介导的冷却模型,包括电子散射的声学声子。通过假设增强的电声声子超碰撞从本地化缺陷在光热电电流生成界面,我们提供了一个更广阔的视角超快的光响应的石墨烯,突出了以前被忽视的影响的接口冷却动力学。我们表明,瞬态光热电响应,这已完全归因于超碰撞,可以成功地解释不拒绝建立光学声子弛豫路径,表明这两种冷却机制不是相互排斥的,而是相辅相成的。

英文摘要:

The broadband and ultrafast photoresponse of graphene has been extensively studied in recent years, although the photoexcited carrier dynamics is still far from being completely understood. Different experimental approaches imply either one of two fundamentally different scattering mechanisms for hot electrons. One is high-energy optical phonons, while the other is disorder-driven supercollisions with acoustic phonons. However, the concurrent relaxation via both optical and acoustic phonons has not been considered so far, hindering the interpretation of different experiments within a unified framework. Here we expand the optical phonon-mediated cooling model, to include electron scattering with the acoustic phonons. By assuming the enhancement of electron-acoustic phonon supercollisions from the localized defect at the photothermoelectric current-generating interface, we provide a broader perspective to the ultrafast photoresponse of graphene, highlighting the previously overlooked effect of the interface for cooling dynamics. We show that the transient photothermoelectric response, which has been attributed exclusively to supercollisions, can be successfully explained without rejecting the established optical phonon relaxation pathway, demonstrating that the two cooling mechanisms are not mutually exclusive but complement each other.

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