Interlayer coupling in two-dimensional MoS2 and phosphorene bilayers: Benchmark quantum Monte Carlo study of interaction energies and quasiparticle band gaps

Abstract

Using high-accuracy many-body quantum Monte Carlo (QMC) methods, we study the effect of interlayer coupling on the properties of two-dimensional freestanding bilayers (BLs) of MoS2 and phosphorene. The properties of the two BL-materials are very different and largely determined by the interlayer interaction, which is purely van der Waals in MoS2 and partially electronic/chemical in phosphorene, resulting in a modest layer-dependent property modulation in MoS2 and strong modulation in phosphorene. Multireference and symmetry considerations are used to construct state-of-the-art accuracy QMC trial wave functions. We determine the quasiparticle band gaps for both materials, ΔqpΓ→K=2.45±0.05eV in BL-MoS2 and ΔqpΓ→Γ=1.59 ±0.1eV in BL-phosphorene. These benchmark band-gap values make it possible to consolidate the interpretation of the widely scattered experimental and theory data.