Resonant and nonresonant spin filtering in bismuthene-silicon cowrie shell-like nanostructures

Abstract

We predict that two distinct strong spin filtering mechanisms in two-terminal geometries at zero magnetic field should be exhibited by bismuthene-silicon nanostructures with cowrie shell-like geometries. One of these is resonant spin filtering where a peak in resonant transmission of one spin species through the nanostructure coincides with an antiresonant transmission dip for the other spin species. The second is strong nonresonant spin filtering where nonresonant transmission of one spin species is much weaker than that of the other spin species. These mechanisms arise from localized electronic states associated with strong disorder and strong spin-orbit coupling in the bismuthene and differ fundamentally from edge state-related spin filtering and from the spin Hall effect. Our density functional theory (DFT)-based simulations suggest that such cowrie shell-like nanostructures can form by spontaneous folding of bismuthene-silicon bilayer domes with armchair edges.