Valley transport in strained silicene heterojunctions with zigzag and armchair interfaces

Abstract

We study the carrier transport through a strained silicene heterojunction based on the tight-binding Hamiltonian, focusing on the effect of the interfaces, i.e., zigzag or armchair, on the valley polarization. We find that inter-valley transmission is prevented in the zigzag configuration owing to the conservation of transverse momentum, but this restriction is lifted for the armchair configuration. More importantly, the preservation of certain valley symmetries of the Fermi surfaces in the zigzag configuration even under strain distortion results in complete cancellation of the valley polarization after summing over all incident angles. In contrast, such symmetries are absent in the forward-propagating states for the strained armchair configuration, resulting in a sizable net valley polarization even after summation over all incident angles. Our findings provide insight toward the key role of interfaces in strained silicene-based valleytronics.