Spatial confinement of excitons in van-der-Waals monolayers induced by electric fields from an adjacent ferroelectric material

Recent studies have demonstrated quantum confinement of excitons in 2D semiconductors by means of localized in-plane electric fields, which act on excitons through their static polarizability. To date, such confinement has been accomplished using lithographically fabricated gates to control the electric fields. An alternative approach is based on localized electric fields created by adjoining ferroelectric materials. Here we examine the influence of the 2D ferroelectric material In₂Se₃, which we study in a dual-gated In₂Se₃/MoSe₂ heterostructure with a thin hBN spacer separating the two selenide crystals. In addition to the expected neutral exciton state, we observe in this structure an additional neutral state, shifted to lower in energy. From the hysteric behavior of the state under electrical gating, we identify it as a field-confined exciton created by the ferroelectric In₂Se₃ layer. A strong polarization anisotropy is also observed in the optical response of the exciton. This suggests exciton localization along a line, which we attribute to the effect of ferroelectric domain boundaries in the In₂Se₃ crystal.