Ultrafast collinear scattering and carrier multiplication in graphene
Ultrafast collinear scattering and carrier multiplication in graphene
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DOI：
10.1038/ncomms2987
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发表时间：
2013-06-01
影响因子：
16.6
通讯作者：
Polini, M.
中科院分区：
文献类型：
--
作者：
Brida, D.;Tomadin, A.;Polini, M.
石墨烯正在成为传统光电、等离子体和纳米光子材料的可行替代品。光与电荷载流子的相互作用产生了一个非平衡分布，它在超快时间尺度上弛豫到热的费米-狄拉克分布，随后冷却了发射声子。虽然较慢的弛豫机制已被广泛研究，初始阶段仍然构成了挑战。实验上，由于极快的亚100 fs载波动态，它们无视大多数泵浦探测设置的分辨率。理论上，无质量的狄拉克费米子代表了一个新的多体问题，与薛定谔费米子有着根本的不同。在这里，我们结合联合收割机泵探测光谱与微观理论研究电子-电子相互作用的早期阶段的放松。我们确定的机制控制的超快动力学，特别是共线散射的作用。这引起了俄歇过程，包括电荷倍增，这是光电压产生和光电探测器的关键。
Graphene is emerging as a viable alternative to conventional optoelectronic, plasmonic and nanophotonic materials. The interaction of light with charge carriers creates an out-of-equilibrium distribution, which relaxes on an ultrafast timescale to a hot Fermi-Dirac distribution, that subsequently cools emitting phonons. Although the slower relaxation mechanisms have been extensively investigated, the initial stages still pose a challenge. Experimentally, they defy the resolution of most pump-probe setups, due to the extremely fast sub-100 fs carrier dynamics. Theoretically, massless Dirac fermions represent a novel many-body problem, fundamentally different from Schrodinger fermions. Here we combine pump-probe spectroscopy with a microscopic theory to investigate electron-electron interactions during the early stages of relaxation. We identify the mechanisms controlling the ultrafast dynamics, in particular the role of collinear scattering. This gives rise to Auger processes, including charge multiplication, which is key in photovoltage generation and photodetectors.