Enhancement of thermoelectric performance of a nanoribbon made of alpha-${\mathcal{T}}_3$ lattice

Abstract

We present electronic and transport properties of a zigzag nanoribbon made of alpha-${\mathcal{T}}_3$ lattice. Our particular focus is on the effects of the continous evolution of the edge modes ( from flat to dispersive) on the thermoelectric transport properties. Unlike the case of graphene nanoribbon, the zigzag nanoribbon of $\alpha -{\mathcal{T}}_3$ lattice can host a pair of dispersive (chiral) 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 chiral 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, thermalconductivity 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 ten 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. However, thermopower is relatively less sensitive to such defects.

To appear in JPCM

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• Holstein polaron in a pseudospin-$1$ quantum spin Hall system: first and second order topological phase transitions
• Electrical and thermal transport through $\alpha -T_3$ NIS junction
• Zigzag dice lattice ribbons: Distinct edge morphologies and structure-spectrum correspondences