  ${\gamma}$-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 ${\gamma}$-GeSe. It is found that
few-layer ${\gamma}$-GeSe are semiconductors with band gaps decreasing with
increasing layer number; and 2D ${\gamma}$-GeSe with layer number $n \geq 2$
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 the 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
${\gamma}$-GeSe promising in spintronic and optoelectric applications.
