Controllable spin splitting in 2D ferroelectric few-layer γ-GeSe

Abstract γ -GeSe is a new type of layered bulk material that was recently successfully synthesized. By means of density functional theory first-principles calculations, we systematically studied the physical properties of two-dimensional (2D) few-layer γ -GeSe. It is found that few-layer γ -GeSe are semiconductors with band gaps decreasing with increasing layer number; and 2D γ -GeSe with layer number n ⩾ 2 are ferroelectric with rather low transition barriers, consistent with the sliding ferroelectric mechanism. Particularly, spin–orbit coupling induced spin splitting is observed at the top of valence band, which can be switched by the ferroelectric reversal; furthermore, their negative piezoelectricity also enables the regulation of spin splitting by strain. Finally, excellent optical absorption was also revealed. These intriguing properties make 2D few-layer γ -GeSe promising in spintronic and optoelectric applications.