In van der Waals bonded or rotationally disordered multilayer stacks of two-dimensional (2D) materials, the electronic states remain tightly confined within individual 2D layers. As a result, electron-phonon interactions occur primarily within layers and interlayer electrical conductivities are low. In addition, strong covalent in-plane intralayer bonding combined with weak van der Waals interlayer bonding results in weak phonon-mediated thermal coupling between the layers. We demonstrate here, however, that Coulomb interactions between electrons in different layers of multilayer epitaxial graphene provide an important mechanism for interlayer thermal transport, even though all electronic states are strongly confined within individual 2D layers. This effect is manifested in the relaxation dynamics of hot carriers in ultrafast time-resolved terahertz spectroscopy. We develop a theory of interlayer Coulomb coupling containing no free parameters that accounts for the experimentally observed trends in hot-carrier dynamics as temperature and the number of layers is varied.

中文翻译：

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通过多层外延石墨烯中的层间库仑耦合进行电子冷却。

在二维（2D）材料的范德华粘合或旋转无序多层堆叠中，电子态保持紧密地限制在​​各个2D层内。结果，电子-声子相互作用主要发生在层内，并且层间电导率低。另外，强共价面内层内键合与弱范德华层间键合导致层之间由声子介导的弱热耦合。但是，我们在这里证明，即使所有电子状态都严格限制在单个2D层中，多层外延石墨烯不同层中电子之间的库仑相互作用为层间热传输提供了重要的机制。这种效应在超快时间分辨太赫兹光谱中热载流子的弛豫动力学中得到体现。我们开发了一种不包含自由参数的层间库仑耦合理论，该理论解释了随着温度和层数的变化，热载流子动力学实验观察到的趋势。