Large spin Seebeck effects in zigzag-edge silicene nanoribbons

Xi-Feng Yang,Xue-Feng Wang,Yu-Shen Liu,Jin-Fu Feng

doi:10.1063/1.4892956

Xi-Feng Yang, Xue-Feng Wang + Show 2 more

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https://doi.org/10.1063/1.4892956

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Abstract

Using the first-principles methods, we investigate the thermospin properties of a two-probe model based on zigzag-edge silicene nanoribbons (ZSiNRs). Compared with the odd-width ZSiNRs, the spin Seebeck coefficient of the even-width ZSiNRs is obviously enhanced at room temperature. This fact is attributed to a nearly perfect symmetry of the linear conductance gap with the different spin index with respect to the Fermi level induced by the different parity of the wave functions. More interestingly, the corresponding charge Seebeck coefficient is near zero. Therefore, when a thermal bias is presented in the even-width ZSiNRs, a nearly pure spin current is achieved. Meanwhile, the spin polarization of the current approaches infinite.

Highlights

Silicene, a monolayer honeycomb network of silicon (Si), has attracted the wide attentions in recent years.[1,2,3,4] Since the silicene possesses a low-buckled structure, some interesting properties have been reported.[5,6,7] according to the edge characteristics, silicene nanoribbons can be divided into zigzag-edge silicene nanoribbons (ZSiNRs) and armchair-edge silicene nanoribbons (ASiNRs)
The 6-ZSiNR has a metallic property at the Fermi level, but its linear conductance Gσ has an obvious gap for the different spin index in the different energy range
Even more interesting is that the linear conductance spectrum for the different spin index has a nearly mirror symmetry to the Fermi level (i.e. G↑(E − EF) G↓(EF − E))

Summary

Introduction

A monolayer honeycomb network of silicon (Si), has attracted the wide attentions in recent years.[1,2,3,4] Since the silicene possesses a low-buckled structure, some interesting properties have been reported.[5,6,7] according to the edge characteristics, silicene nanoribbons can be divided into zigzag-edge silicene nanoribbons (ZSiNRs) and armchair-edge silicene nanoribbons (ASiNRs). Since the spin Seebeck effect was first observed in ferromagnetic materials,[11] a novel research field, called spin caloritronics, has been widely investigated in various systems.[12,13,14,15,16,17] In addition, Zeng et al investigated a thermal magnetoresistance effect in graphene-based thermospin devices by switching the magnetic configurations.[18] The high spin polarization and large spin Seebeck effect at the Fermi level can be simultaneously achieved in graphene-based thermospin devices by the edge doping.[19] Very recently, Zberecki et al found the spin thermopower could be enhanced by properly arranging impurities.[20]

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Conclusion