Controlling inelastic light scattering quantum pathways in graphene
Controlling inelastic light scattering quantum pathways in graphene
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DOI：
10.1038/nature09866
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发表时间：
2011-03-31
期刊：
影响因子：
64.8
通讯作者：
Wang, Feng
中科院分区：
文献类型：
--
作者：
Chen, Chi-Fan;Park, Cheol-Hwan;Wang, Feng
非弹性光散射光谱学，因为它的第一个发现（1，2），是一个不可或缺的工具，在物理科学中探测基本激发，如声子（3），磁振子（4）和等离子体激元（5）在散装和纳米材料。在非弹性光散射的量子力学图像中，入射光子首先激发一组中间电子态，然后产生晶体基元激发并辐射能量移动的光子（6）。因此，中间电子激发在非弹性光散射中作为量子路径具有关键作用，这可以通过共振拉曼散射（6）和拉曼干涉（7，8）来举例说明。控制这些激发途径的能力可以为探测、操纵和利用非弹性光散射开辟新的机会。在这里，我们实现了静电掺杂石墨烯的激发途径控制。我们的研究揭示了石墨烯中不同拉曼途径之间的量子干涉：当一些途径被阻断时，单声子拉曼强度不会像通常预期的那样减弱，而是急剧增加。这一发现为理解石墨烯中的共振拉曼散射提供了新的思路。此外，我们证明了热电子发光9在石墨烯的费米能量接近一半的激光激发能量。这种热发光是非弹性光散射的另一种形式，它是由激发态弛豫通道引起的，这种通道只在重掺杂的石墨烯中才能得到。
Inelastic light scattering spectroscopy has, since its first discovery(1,2), been an indispensable tool in physical science for probing elementary excitations, such as phonons(3), magnons(4) and plasmons(5) in both bulk and nanoscale materials. In the quantum mechanical picture of inelastic light scattering, incident photons first excite a set of intermediate electronic states, which then generate crystal elementary excitations and radiate energy-shifted photons(6). The intermediate electronic excitations therefore have a crucial role as quantum pathways in inelastic light scattering, and this is exemplified by resonant Raman scattering(6) and Raman interference(7,8). The ability to control these excitation pathways can open up new opportunities to probe, manipulate and utilize inelastic light scattering. Here we achieve excitation pathway control in graphene with electrostatic doping. Our study reveals quantum interference between different Raman pathways in graphene: when some of the pathways are blocked, the one-phonon Raman intensity does not diminish, as commonly expected, but increases dramatically. This discovery sheds new light on the understanding of resonance Raman scattering in graphene. In addition, we demonstrate hot-electron luminescence9 in graphene as the Fermi energy approaches half the laser excitation energy. This hot luminescence, which is another form of inelastic light scattering, results from excited-state relaxation channels that become available only in heavily doped graphene.