Alam Mir Waqas, Souayeh Basma, Islam Sk Firoz
Department of Physics, College of Science, King Faisal University, Al-Hassa 31982, PO Box 400, Saudi Arabia.
Institute of Physics, Sachivalaya Marg, Bhubaneswar-751005, India.
J Phys Condens Matter. 2019 Sep 6;31(48). doi: 10.1088/1361-648X/ab3bf6.
We present electronic and transport properties of a zigzag nanoribbon made oflattice. Our particular focus is on the effects of the continuous evolution of the edge modes (from flat to dispersive) on the thermoelectric transport properties. Unlike the case of graphene nanoribbon, the zigzag nanoribbon oflattice can host a pair of dispersive edge modes at the two valleys for specific width of the ribbon. Moreover, gap opening can also occur at the two valleys depending on the width. The slope of the dispersive edge modes and the energy gap strongly depend on the relative strength of two kinds of hoping parameters present in the system. We compute corresponding transport coefficients such as conductance, thermopower, thermal conductance and the thermoelectric figure of merits by using the tight-binding Green function formalism, in order to explore the roles of the dispersive edge modes. It is found that the thermopower and thermoelectric figure of merits can be enhanced significantly by suitably controlling the edge modes. The figure of merits can be enhanced by thirty times under suitable parameter regime in comparison to the case of graphene. Finally, we reveal that the presence of line defect, close to the edge, can cause a significant impact on the edge modes as well as on electrical conductance and thermopower.
我们展示了由晶格制成的锯齿形纳米带的电学和输运性质。我们特别关注边缘模式（从平坦到色散）的连续演化对热电输运性质的影响。与石墨烯纳米带的情况不同，晶格的锯齿形纳米带在特定宽度的带状结构的两个能谷中可以容纳一对色散边缘模式。此外，根据宽度的不同，两个能谷处也可能出现能隙打开的情况。色散边缘模式的斜率和能隙强烈依赖于系统中存在的两种跳跃参数的相对强度。我们使用紧束缚格林函数形式计算了相应的输运系数，如电导、热电势、热导和热电优值，以探究色散边缘模式的作用。结果发现，通过适当控制边缘模式，可以显著提高热电势和热电优值。与石墨烯的情况相比，在合适的参数范围内，优值可以提高三十倍。最后，我们揭示了靠近边缘的线缺陷的存在会对边缘模式以及电导和热电势产生显著影响。
