Extremely ImprovedInterlayer Exciton Lifetime byAsymmetric Sliding Ferroelectricity in Transition Metal DichalcogenideHeterobilayers

Recently, van der Waals (vdW) heterobilayers have attracted much attention, especially due to their type II band alignments and the lowest-energy excitonic state formed by interlayer excitons. In this work, based on the GW + BSE method, we investigate the ferroelectric and optical properties of transition metal dichalcogenide (TMD) heterobilayers and reveal the important role of interlayer charge distribution tuned by sliding ferroelectricity in deciding the excited-state properties, including the band alignment and interlayer exciton lifetime. Due to the asymmetric structure of TMD heterobilayers, the polarized states are divided into polar-up (P_↑) states and polar-down (P_↓) states. In particular, the interlayer exciton lifetime of P_↑ states exhibits a 2 order-of-magnitude improvement compared to TMD monolayers, while the exciton lifetime of P_↓ states can be further enhanced by an order of magnitude. We also provide an effective understanding of the essential physics of correlations between interlayer exciton lifetime and interlayer charge distribution, which allows the extension to other heterobilayers. Our work clarifies the physical picture of interlayer excitons tuned by sliding ferroelectricity and provides a new path to control excited-state properties of vdW heterobilayer optoelectronic devices.