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Coherent control of current injection in zigzag graphene nanoribbons

机译：之字形石墨烯纳米带电流注入的相干控制

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摘要

We present Fermi's "golden rule" calculations of the optical carrier injection and the coherent control of current injection in graphene nanoribbons with zigzag geometry, using an envelope function approach. This system possesses strongly localized states (flat bands) with a large joint density of states at low photon energies; for ribbons with widths above a few tens of nanometers, this system also posses large number of (nonflat) states with maxima and minima close to the Fermi level. Consequently, even with small dopings the occupation of these localized states can be significantly altered. In this work, we calculate the relevant quantities for coherent control at different chemical potentials, showing the sensitivity of this system to the occupation of the edge states. We consider coherent control scenarios arising from the interference of one-photon absorption at 2hω with two-photon absorption at hω, and those arising from the interference of one-photon absorption at hω with stimulated electronic Raman scattering (virtual absorption at 2hω followed by emission at hω. Although at large photon energies these processes follow an energy-dependence similar to that of 2D graphene, the zigzag nanoribbons exhibit a richer structure at low photon energies, arising from divergences of the joint density of states and from resonant absorption processes, which can be strongly modified by doping. As a figure of merit for the injected carrier currents, we calculate the resulting swarm velocities. Finally, we provide estimates for the limits of validity of our model.
机译：我们使用包络函数方法，对具有锯齿形几何形状的石墨烯纳米带中的光载波注入和电流注入的相干控制提出了费米的“黄金法则”。该系统具有强局部化态​​（平坦带），在低光子能量下具有大的联合态密度。对于宽度超过几十纳米的色带，该系统还具有大量（非平坦）状态，其最大值和最小值接近费米能级。因此，即使使用少量掺杂，也可以显着改变这些局部状态的占有率。在这项工作中，我们计算了在不同化学势下进行相干控制的相关量，显示了该系统对边缘态占据的敏感性。我们考虑了由2hω处的一个光子吸收与hω处的两个光子吸收的干扰引起的相干控制方案，以及由hω处的一个光子吸收与受激电子拉曼散射的干扰引起的相干控制方案（在2hω处的虚拟吸收然后发射）尽管在大光子能量下，这些过程遵循类似于二维石墨烯的能量依赖性，但之字形纳米带在低光子能量下表现出更丰富的结构，这是由于状态的联合密度的发散和共振吸收过程所致。可以通过掺杂来强力修改。作为注入的载流子的品质因数，我们计算了形成的群速度，最后，提供了对模型有效性极限的估计。

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  • 来源
    《Physical review》 |2016年第7期|075442.1-075442.16|共16页
  • 作者

    Cuauhtemoc Salazar; J. L. Cheng; J. E. Sipe;

  • 作者单位

    Department of Physics and Institute of Optical Sciences, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada, M5S 1A7;

    Department of Physics and Institute of Optical Sciences, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada, M5S 1A7,Brussels Photonics Team (B-PHOT), Department of Applied Physics and Photonics (IR-TONA), Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussel, Belgium;

    Department of Physics and Institute of Optical Sciences, University of Toronto, 60 St. George Street, Toronto, Ontario, Canada, M5S 1A7;

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