Quasiparticle band structures, spontaneous polarization, and spin-splitting in noncentrosymmetric few-layer and bulk $\gamma$-GeSe

Abstract

Group-IV monochalcogenides have attracted much attention due to their potential of ferroelectric and multiferroic properties. Recently, centrosymmetric gamma-phase GeSe in a double-layer honeycomb lattice has been theoretically predicted, but the synthesized gamma-phase GeSe showed a noncentrosymmetric atomic structure, leading to the possibility of ferroelectricity and spin-splitting. Here, we study the quasiparticle band structures, spontaneous polarization, and spin-splitting in noncentrosymmetric gamma-GeSe using density functional theory and GW calculations. Our results show that noncentrosymmetric few-layer and bulk gamma-GeSe have semiconducting band structures with indirect band gaps, which depend almost linearly on the reciprocal of the number of layers. Spontaneous polarization occurs due to a small charge transfer between the layers, which increases with compressive strain, and ferroelectric switching can be achieved by an interlayer translation with a small energy barrier. Spin-splitting is found to be more significant at the highest valence band than at the lowest conduction band. Our results provide insights into the fundamental electronic properties of a layered ferroelectric semiconductor applicable to devices with ferroelectric/nonferroelectric junctions.

9 pages, 8 figures, 2 tables

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• Abnormal behavior of preferred formation of cationic vacancy from the interior in γ-GeSe monolayer with the stereo-chemical antibonding lone-pair state