Mihnev Momchil T, Tolsma John R, Divin Charles J, Sun Dong, Asgari Reza, Polini Marco, Berger Claire, de Heer Walt A, MacDonald Allan H, Norris Theodore B
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
Center for Ultrafast Optical Science, University of Michigan, Ann Arbor, Michigan 48109, USA.
Nat Commun. 2015 Sep 24;6:8105. doi: 10.1038/ncomms9105.
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.
在范德华键合或旋转无序的二维（2D）材料多层堆叠中，电子态被紧密限制在各个二维层内。因此，电子 - 声子相互作用主要发生在层内，层间电导率较低。此外，强共价面内层内键合与弱范德华层间键合相结合，导致层间声子介导的热耦合较弱。然而，我们在此证明，多层外延石墨烯不同层中的电子之间的库仑相互作用为层间热传输提供了重要机制，尽管所有电子态都被强烈限制在各个二维层内。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表现出来。我们开发了一种不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变化，热载流子动力学中实验观察到的趋势。
