Circular photogalvanic effect in an inversion-symmetry-broken bilayer germanium nanosheet

TL;DR

This study demonstrates spin-to-charge conversion via the circular photogalvanic effect in inversion-symmetry-broken bilayer germanium nanosheets, highlighting the role of the top layer and intrinsic germanene properties.

Contribution

It reveals the dominant contribution of the top layer in bilayer germanium nanosheets to the CPGE and links the effect to the intrinsic properties of germanene with broken inversion symmetry.

Findings

Maximum CPGE current in bilayer germanene

Top layer mainly contributes to spin-to-charge conversion

Potential relation to intrinsic germanene features

Abstract

Spin-to-charge conversion in monolayer and bilayer germanium(Ge) nanosheets was demonstrated via the circular photogalvanic effect (CPGE). The CPGE current generated in a spin-splitting state of the Ge nanosheet reached a maximum value when the thickness of the Ge nanosheet corresponded to bilayer germanene, indicating that the top layer of the bilayer Ge nanosheet mainly contributed to the spin-to-charge conversion. Because the hybridization of orbitals is suppressed by isolation from the bottom Al layer for the top Ge nanosheet, the observed spin-to-charge conversion has a possibility to be related to the intrinsic features of germanene with breaking of inversion symmetry.