Reversible out-of-plane spin texture in a two-dimensional ferroelectric material for persistent spin helix

Although spin-orbit coupling (SOC) in ferroelectrics contributes to the manipulation of the electron spin by an electric field, it also breaks the spin rotation symmetry resulting in the decay of spin polarization. Here, we showed that the [110] Dresselhaus model in the two-dimensional ferroelectrics with in-plane ferroelectricity can host a persistent spin helix and render the spin lifetime infinite. Taking a WO2Cl2 monolayer as an example, we demonstrated from first principles that SOC leads to a sizable [110] Dresselhaus-type band splitting near the conduction-band minimum accompanied by an out-of-plane Dresselhaus-type spin texture which is decisive for a long spin lifetime. More interestingly, such a spin texture can be reversed by switching the ferroelectric polarization, suggesting the fully electrically controllable persistent spin helix. Our findings uncover the possibility of an electrically controllable persistent spin helix in ferroelectrics, offering a promising platform for novel spintronics applications.