Edge magnetism impact on electrical conductance and thermoelectric properties of graphenelike nanoribbons

TL;DR

This study investigates how magnetic edge states in narrow zigzag nanoribbons influence their electrical and thermoelectric properties, revealing potential for high thermoelectric efficiency and spin-polarized conductance in materials like silicene, germanene, and stanene.

Contribution

It demonstrates the impact of magnetic edge states on electronic band structure, conductance, and thermoelectric performance, highlighting the effects of gate voltage and potential for high thermoelectric figures of merit.

Findings

Seebeck coefficient and power factor are enhanced near charge neutrality.

Gate voltage induces spin-polarized conductance and reduces thermoelectric efficiency.

Room-temperature figure of merit can exceed 3 with phonon thermal conductance reduction.

Abstract

Edge states in narrow quasi two-dimensional nanostructures determine, to a large extent, their electric, thermoelectric and magnetic properties. Non-magnetic edge states may quite often lead to topological insulator type behavior. However another scenario develops when the zigzag edges are magnetic and the time reversal symmetry is broken. In this work we report on the electronic band structure modifications, electrical conductance and thermoelectric properties of narrow zigzag nanoribbons with spontaneously magnetized edges. Theoretical studies based on the Kane-Mele- Hubbard tight-binding model show that for silicene, germanene and stanene both the Seebeck coefficient and the thermoelectric power factor are strongly enhanced for energies close to the charge neutrality point. Perpendicular gate voltage lifts the spin degeneracy of energy bands in the ground state with antiparallel magnetized zigzag edges and makes the electrical conductance significantly spin-polarized. Simultaneously the gate voltage worsens the thermoelectric performance. Estimated room-temperature figures of merit for the aforementioned nanoribbons can exceed a value of 3 if phonon thermal conductances are adequately reduced.